1 00:00:01,680 --> 00:00:04,080 The following content is provided under a Creative 2 00:00:04,080 --> 00:00:05,620 Commons license. 3 00:00:05,620 --> 00:00:07,920 Your support will help MIT OpenCourseWare 4 00:00:07,920 --> 00:00:12,280 continue to offer high quality, educational resources for free. 5 00:00:12,280 --> 00:00:14,910 To make a donation, or view additional materials 6 00:00:14,910 --> 00:00:18,870 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:18,870 --> 00:00:21,360 at ocw.mit.edu. 8 00:00:21,360 --> 00:00:22,860 JESSICA SOMMERVILLE: So this morning 9 00:00:22,860 --> 00:00:24,930 we heard Laura give a really beautiful overview 10 00:00:24,930 --> 00:00:26,747 of her research program, and my talk today 11 00:00:26,747 --> 00:00:28,330 is going to be a little bit different. 12 00:00:28,330 --> 00:00:29,700 I'm going to talk about some things that 13 00:00:29,700 --> 00:00:31,399 are going to be highly related to what 14 00:00:31,399 --> 00:00:32,940 Laura was talking about, particularly 15 00:00:32,940 --> 00:00:34,320 at the end of her talk. 16 00:00:34,320 --> 00:00:37,350 But because this is like brand new hot off the press work, 17 00:00:37,350 --> 00:00:40,860 some of it's actually ongoing as you'll see as the talk unfolds. 18 00:00:40,860 --> 00:00:43,650 I'm going to be focusing on a more kind of specific detail 19 00:00:43,650 --> 00:00:44,150 level. 20 00:00:44,150 --> 00:00:46,108 So I may tell you about four different studies, 21 00:00:46,108 --> 00:00:48,779 three of which are completed, one of which is ongoing. 22 00:00:48,779 --> 00:00:50,820 And they all have to do with infants' sensitivity 23 00:00:50,820 --> 00:00:53,270 to costs and benefits. 24 00:00:53,270 --> 00:00:54,190 OK. 25 00:00:54,190 --> 00:00:56,332 So, as we all know, cost benefit analyses 26 00:00:56,332 --> 00:00:57,790 are really central to the decisions 27 00:00:57,790 --> 00:01:00,105 we make at both a conscious and an unconscious level. 28 00:01:00,105 --> 00:01:02,230 And, of course, there's all kinds of different ways 29 00:01:02,230 --> 00:01:03,861 that we make decisions, right? 30 00:01:03,861 --> 00:01:05,319 But one of the things that we often 31 00:01:05,319 --> 00:01:07,000 do when we're making a decision is 32 00:01:07,000 --> 00:01:10,660 we think about what rewards do we anticipate from following 33 00:01:10,660 --> 00:01:12,594 a particular course of action, and how 34 00:01:12,594 --> 00:01:14,260 do those compare to the costs that we'll 35 00:01:14,260 --> 00:01:16,900 incur from performing that same action. 36 00:01:16,900 --> 00:01:18,580 And we will act in a sense to try 37 00:01:18,580 --> 00:01:22,179 to maximize the value that we get out of a particular choice. 38 00:01:22,179 --> 00:01:24,220 That's true of simple decisions like this, right? 39 00:01:24,220 --> 00:01:26,553 This woman deciding what she's going to eat for dessert. 40 00:01:26,553 --> 00:01:28,180 And we can also apply these analyses 41 00:01:28,180 --> 00:01:29,950 to more complex decisions, like things 42 00:01:29,950 --> 00:01:32,449 like where we're going to go to college, what kind of career 43 00:01:32,449 --> 00:01:34,750 are we going to pursue, where are we going to live. 44 00:01:34,750 --> 00:01:35,339 OK. 45 00:01:35,339 --> 00:01:37,630 One of the things that we heard from Laura this morning 46 00:01:37,630 --> 00:01:39,721 is that cost benefit analyses don't just 47 00:01:39,721 --> 00:01:41,970 apply to her own behavior and her own decision making. 48 00:01:41,970 --> 00:01:43,720 She showed some really neat evidence 49 00:01:43,720 --> 00:01:46,150 that these types of analyses form 50 00:01:46,150 --> 00:01:48,970 the basis for the inferences that we make about other people 51 00:01:48,970 --> 00:01:51,010 and that we make about their behavior. 52 00:01:51,010 --> 00:01:53,140 So that raises the very interesting question 53 00:01:53,140 --> 00:01:55,605 of the developmental origins of these types analyses. 54 00:01:55,605 --> 00:01:56,980 And that's what I'm going to talk 55 00:01:56,980 --> 00:01:58,355 about today, infants' sensitivity 56 00:01:58,355 --> 00:02:00,872 to costs and benefits. 57 00:02:00,872 --> 00:02:03,080 My talk is going to kind of have two different parts. 58 00:02:03,080 --> 00:02:04,496 In the first part, I'm going to be 59 00:02:04,496 --> 00:02:05,950 talking about cases where infants 60 00:02:05,950 --> 00:02:07,720 are observing other people. 61 00:02:07,720 --> 00:02:10,120 And what the question that I'm asking there is 62 00:02:10,120 --> 00:02:13,210 do infants-- are they able to register the costs that are 63 00:02:13,210 --> 00:02:15,425 behind other people's actions? 64 00:02:15,425 --> 00:02:17,050 And then in the second part of my talk, 65 00:02:17,050 --> 00:02:18,250 I'm actually going to switch gears, 66 00:02:18,250 --> 00:02:20,440 and I'm going to talk about infants' registration 67 00:02:20,440 --> 00:02:23,579 and minimization of costs, the registration of benefits, 68 00:02:23,579 --> 00:02:25,870 to guide their own behavior, their own decision making. 69 00:02:25,870 --> 00:02:27,872 I'm going to talk about a particular test case. 70 00:02:27,872 --> 00:02:30,205 And that's the test case of infants' prosocial behavior. 71 00:02:33,310 --> 00:02:34,180 OK. 72 00:02:34,180 --> 00:02:35,860 And I want to be kind of specific here. 73 00:02:35,860 --> 00:02:37,450 So across all of these studies, I'm 74 00:02:37,450 --> 00:02:39,250 talking about cost in one particular way. 75 00:02:39,250 --> 00:02:40,750 Of course, there's all kinds of ways 76 00:02:40,750 --> 00:02:42,640 you could operationalize cost. 77 00:02:42,640 --> 00:02:44,470 But what we've been focusing on so far 78 00:02:44,470 --> 00:02:46,540 is physical effort, the physical effort 79 00:02:46,540 --> 00:02:48,880 behind an action as a cost. 80 00:02:48,880 --> 00:02:50,662 Why would we start here? 81 00:02:50,662 --> 00:02:52,620 Well, there's several different reasons, right? 82 00:02:52,620 --> 00:02:55,090 And the basic kind of evolutionary level, it's 83 00:02:55,090 --> 00:02:57,910 really important that we can register 84 00:02:57,910 --> 00:03:00,070 and that we can minimize energetic costs, 85 00:03:00,070 --> 00:03:01,150 effortful costs, right? 86 00:03:01,150 --> 00:03:02,830 Our very survival depends on that. 87 00:03:02,830 --> 00:03:05,050 We have to metabolically and energetically budget, 88 00:03:05,050 --> 00:03:07,044 or we won't stick around, right? 89 00:03:07,044 --> 00:03:08,710 So that gives us good reason that that's 90 00:03:08,710 --> 00:03:11,860 a good starting place in terms of looking at young infants' 91 00:03:11,860 --> 00:03:16,390 ability to register costs and minimize cost potentially. 92 00:03:16,390 --> 00:03:19,240 Another reason is that for decades, scholars 93 00:03:19,240 --> 00:03:22,970 have really given a central role to effort in decision-making. 94 00:03:22,970 --> 00:03:24,490 And this dates back to the 1940s, 95 00:03:24,490 --> 00:03:26,170 the whole in Solomon who postulated 96 00:03:26,170 --> 00:03:27,580 the law of least effort. 97 00:03:27,580 --> 00:03:30,406 So the idea here is that if there are two lines of actions 98 00:03:30,406 --> 00:03:31,780 that lead to equal rewards, we're 99 00:03:31,780 --> 00:03:33,863 going to take the path of least resistance, right? 100 00:03:33,863 --> 00:03:36,250 We're going to seek to minimize effort. 101 00:03:36,250 --> 00:03:38,530 And then, finally, in more contemporary work 102 00:03:38,530 --> 00:03:40,570 that's looked at cost-benefit decision-making, 103 00:03:40,570 --> 00:03:43,120 both in adults and in nonhuman animals, a lot of this work 104 00:03:43,120 --> 00:03:46,530 comes from the neuroimaging literature. 105 00:03:46,530 --> 00:03:49,125 Effort has been a fairly heavily studied cost. 106 00:03:49,125 --> 00:03:50,500 So this is a good starting place, 107 00:03:50,500 --> 00:03:52,583 because we have a pretty good understanding of how 108 00:03:52,583 --> 00:03:55,030 effort and various benefits or reward are integrated 109 00:03:55,030 --> 00:03:57,010 at both the neural and a behavioral level, 110 00:03:57,010 --> 00:04:01,930 at least for nonhuman animals and for human adults. 111 00:04:01,930 --> 00:04:02,740 OK. 112 00:04:02,740 --> 00:04:04,690 So the first question we might ask 113 00:04:04,690 --> 00:04:06,820 is, what is the existing evidence 114 00:04:06,820 --> 00:04:08,710 in terms of the question of whether infants 115 00:04:08,710 --> 00:04:11,909 have a basic ability to register cost behind actions. 116 00:04:11,909 --> 00:04:13,450 And there's really two different ways 117 00:04:13,450 --> 00:04:14,620 we could pose this question. 118 00:04:14,620 --> 00:04:16,899 We can think about the question with respect 119 00:04:16,899 --> 00:04:19,390 to infants own behavior, their own actions. 120 00:04:19,390 --> 00:04:23,260 Is there evidence that infants will act to recognize costs 121 00:04:23,260 --> 00:04:25,890 and to minimize costs in their own behavior. 122 00:04:25,890 --> 00:04:27,640 The other way that we can ask the question 123 00:04:27,640 --> 00:04:29,980 is in terms of infants observation of other people's 124 00:04:29,980 --> 00:04:30,480 behavior. 125 00:04:30,480 --> 00:04:34,972 Do they recognize the cost behind other people's actions. 126 00:04:34,972 --> 00:04:36,430 You know, surprisingly there really 127 00:04:36,430 --> 00:04:38,290 hasn't been a lot of work that's looked directly 128 00:04:38,290 --> 00:04:40,000 at this when we're talking about infants 129 00:04:40,000 --> 00:04:42,620 own behavior, their own decision making. 130 00:04:42,620 --> 00:04:44,970 There is some work from the weight perception literature 131 00:04:44,970 --> 00:04:46,660 that's looked at how infants interact 132 00:04:46,660 --> 00:04:48,049 with blocks of different ways. 133 00:04:48,049 --> 00:04:49,840 And so what people will do in these studies 134 00:04:49,840 --> 00:04:52,215 is they'll present little babies, nine-month-old infants, 135 00:04:52,215 --> 00:04:55,030 with two blocks that look virtually identical. 136 00:04:55,030 --> 00:04:56,560 They only differ from one another 137 00:04:56,560 --> 00:04:58,665 in terms of their respective weights. 138 00:04:58,665 --> 00:05:00,040 And what these studies have shown 139 00:05:00,040 --> 00:05:02,260 is if you give infants a choice between these two objects, 140 00:05:02,260 --> 00:05:04,330 they'll systematically prefer the light object 141 00:05:04,330 --> 00:05:05,897 over the heavy object. 142 00:05:05,897 --> 00:05:08,230 So one way to think about these findings is what infants 143 00:05:08,230 --> 00:05:10,840 are doing here is exactly what we're interested 144 00:05:10,840 --> 00:05:12,850 in, they're minimizing the physical cost, right? 145 00:05:12,850 --> 00:05:15,756 They're taking the past of-- the path of least effort. 146 00:05:15,756 --> 00:05:17,380 One challenge, though, for interpreting 147 00:05:17,380 --> 00:05:19,630 these finding is oftentimes in these studies, 148 00:05:19,630 --> 00:05:21,130 the heavy blocks that are being used 149 00:05:21,130 --> 00:05:23,370 are beyond infants lifting capacity. 150 00:05:23,370 --> 00:05:25,870 So what that means is it's hard to know if these results are 151 00:05:25,870 --> 00:05:27,874 about infants registering cost per se, 152 00:05:27,874 --> 00:05:29,290 or if what we're really getting at 153 00:05:29,290 --> 00:05:32,500 is just infants repeating a sort of successful interaction 154 00:05:32,500 --> 00:05:35,960 with an object that they've acted on previously. 155 00:05:35,960 --> 00:05:36,460 OK. 156 00:05:36,460 --> 00:05:38,680 So Laura talked a little bit about this in her talk today. 157 00:05:38,680 --> 00:05:40,680 What about the evidence of registration of costs 158 00:05:40,680 --> 00:05:41,971 and other people's actions. 159 00:05:41,971 --> 00:05:43,720 And one of the things that Laura mentioned 160 00:05:43,720 --> 00:05:46,030 that we know from many, many different studies, 161 00:05:46,030 --> 00:05:48,370 is that infants appear to expect efficiency 162 00:05:48,370 --> 00:05:49,870 in other people's actions. 163 00:05:49,870 --> 00:05:51,490 Laura showed you one example of that. 164 00:05:51,490 --> 00:05:52,760 I'll show you a different example 165 00:05:52,760 --> 00:05:54,510 of that, which comes from actually a study 166 00:05:54,510 --> 00:05:56,709 that Liz did with one of her graduate students. 167 00:05:56,709 --> 00:05:58,250 So here we see someone who's reaching 168 00:05:58,250 --> 00:06:00,080 over a barrier in order to get an object. 169 00:06:00,080 --> 00:06:01,670 The barrier is then removed. 170 00:06:01,670 --> 00:06:03,870 Infants have the expectation that that person 171 00:06:03,870 --> 00:06:05,620 is going to reach directly for the object, 172 00:06:05,620 --> 00:06:08,640 right, rather than performing that funny arcing motion. 173 00:06:08,640 --> 00:06:10,730 So, again, one way to think about these findings 174 00:06:10,730 --> 00:06:12,260 is that what infants are doing is 175 00:06:12,260 --> 00:06:14,060 they're expecting that the person is going to take 176 00:06:14,060 --> 00:06:15,380 the least costly action, right? 177 00:06:15,380 --> 00:06:17,510 And, in fact, there's all kinds of costs 178 00:06:17,510 --> 00:06:19,430 to this particular arcing motion, right? 179 00:06:19,430 --> 00:06:21,950 It's indirect, it probably takes longer, 180 00:06:21,950 --> 00:06:26,396 it's probably more difficult, it's more effortful. 181 00:06:26,396 --> 00:06:28,145 And so we wanted to ask the question, too, 182 00:06:28,145 --> 00:06:31,550 to begin with if infants were able to register costs. 183 00:06:31,550 --> 00:06:33,320 But unlike in this situation where 184 00:06:33,320 --> 00:06:35,740 there's multiple potentially redundant cues 185 00:06:35,740 --> 00:06:38,630 that this arching motion is a costly behavior, 186 00:06:38,630 --> 00:06:40,310 we wanted to really kind of focus 187 00:06:40,310 --> 00:06:42,830 in on situations in which there aren't 188 00:06:42,830 --> 00:06:45,980 a lot of overt observable cues to the costs underlying 189 00:06:45,980 --> 00:06:46,980 another person's action. 190 00:06:50,100 --> 00:06:52,680 So the way that we did this is we showed infants 191 00:06:52,680 --> 00:06:56,820 different actions that look similar on their surface level, 192 00:06:56,820 --> 00:06:58,299 but these actions differ in terms 193 00:06:58,299 --> 00:07:00,840 of the degree of physical effort that are required to perform 194 00:07:00,840 --> 00:07:02,490 them, and the way that we achieve 195 00:07:02,490 --> 00:07:05,464 that is by having infants watch people lift objects 196 00:07:05,464 --> 00:07:06,630 of different weights, right? 197 00:07:06,630 --> 00:07:10,180 So, obviously, heavy weighted objects are harder to lift. 198 00:07:10,180 --> 00:07:14,830 They're more effortly costly than lifting a light object. 199 00:07:14,830 --> 00:07:17,070 And what we wanted to know is can infants 200 00:07:17,070 --> 00:07:20,400 recognize under conditions where they have really minimal, 201 00:07:20,400 --> 00:07:23,280 observable cues, no cues about, for example, straining 202 00:07:23,280 --> 00:07:24,810 or sweating or things like that that 203 00:07:24,810 --> 00:07:27,480 might be really obvious for figuring out the effort. 204 00:07:27,480 --> 00:07:30,109 Will they be able to understand that when someone is lifting 205 00:07:30,109 --> 00:07:32,400 a heavy block, that's a more effortful action than when 206 00:07:32,400 --> 00:07:35,460 they're lifting a light block. 207 00:07:35,460 --> 00:07:37,390 In addition to that kind of primary question, 208 00:07:37,390 --> 00:07:39,990 we were also interested in whether this ability in infants 209 00:07:39,990 --> 00:07:42,074 might be individually variable. 210 00:07:42,074 --> 00:07:43,740 So this might come as a surprise to you, 211 00:07:43,740 --> 00:07:46,755 but infants, like adults, are individually variable. 212 00:07:46,755 --> 00:07:48,630 And they're individually variable, of course, 213 00:07:48,630 --> 00:07:49,380 in many ways. 214 00:07:49,380 --> 00:07:51,450 But one way in which they vary from one another 215 00:07:51,450 --> 00:07:53,199 is in terms of how strong they are, right? 216 00:07:53,199 --> 00:07:54,880 Just like human adults, right? 217 00:07:54,880 --> 00:07:57,900 We're variable in terms of how strong we are. 218 00:07:57,900 --> 00:08:00,240 And we have an idea, or hypothesis, 219 00:08:00,240 --> 00:08:02,820 that infants individual differences in strength 220 00:08:02,820 --> 00:08:05,029 might actually be important for registering 221 00:08:05,029 --> 00:08:07,320 the effort-related costs behind these different lifting 222 00:08:07,320 --> 00:08:09,502 actions with different weighted objects. 223 00:08:09,502 --> 00:08:11,460 One of the reasons that they might be important 224 00:08:11,460 --> 00:08:14,580 is because of core strength gates the type of experience 225 00:08:14,580 --> 00:08:17,250 that infants are going to have in their everyday life, right? 226 00:08:17,250 --> 00:08:19,860 If you're a strong baby, you can lift heavier objects 227 00:08:19,860 --> 00:08:20,820 than a weak baby. 228 00:08:20,820 --> 00:08:24,030 You can also lift a wider contrast of range of objects, 229 00:08:24,030 --> 00:08:24,750 right? 230 00:08:24,750 --> 00:08:26,370 So we thought maybe there's something 231 00:08:26,370 --> 00:08:29,100 about individual differences in strength, particularly, 232 00:08:29,100 --> 00:08:30,930 for babies who are stronger where they'll 233 00:08:30,930 --> 00:08:33,960 be better at recognizing the differential effort that 234 00:08:33,960 --> 00:08:35,610 goes along with lifting actions when 235 00:08:35,610 --> 00:08:38,980 you're talking about blocks of different weight. 236 00:08:38,980 --> 00:08:39,480 OK. 237 00:08:39,480 --> 00:08:41,010 So let me tell you about the study 238 00:08:41,010 --> 00:08:43,559 that we conducted to ask this question. 239 00:08:43,559 --> 00:08:45,570 We tested 12-month-old infants in this study. 240 00:08:45,570 --> 00:08:47,880 They took part in a turn taking procedure 241 00:08:47,880 --> 00:08:49,920 where we recorded EEG, electrical activity 242 00:08:49,920 --> 00:08:52,580 from the brain as it propagates the scalp. 243 00:08:52,580 --> 00:08:55,050 And in the course of this task, what they did is 244 00:08:55,050 --> 00:08:57,470 they took part in different types of trials. 245 00:08:57,470 --> 00:09:00,720 On observation trials, they would watch an experimenter who 246 00:09:00,720 --> 00:09:03,720 would lift these different objects or these blocks, 247 00:09:03,720 --> 00:09:06,030 and these blocks looked perceptually identical 248 00:09:06,030 --> 00:09:07,240 in terms of size and shape. 249 00:09:07,240 --> 00:09:09,300 They were different colors so infants could individuate them 250 00:09:09,300 --> 00:09:12,090 and keep track of them, but what varied from trial to trial 251 00:09:12,090 --> 00:09:13,980 was exactly how much the objects weighed. 252 00:09:13,980 --> 00:09:17,700 So they range from being the weight of a typical bath toy 253 00:09:17,700 --> 00:09:19,500 to being quite heavy. 254 00:09:19,500 --> 00:09:21,689 So infants can lift the heaviest blocks, 255 00:09:21,689 --> 00:09:23,730 but they're pretty effortful in order for infants 256 00:09:23,730 --> 00:09:25,200 to be able to lift them. 257 00:09:25,200 --> 00:09:27,810 In the trials where they watched an experiment or interact 258 00:09:27,810 --> 00:09:29,268 with these blocks, the experimenter 259 00:09:29,268 --> 00:09:31,740 would do things like put the block up on a platform, 260 00:09:31,740 --> 00:09:35,370 drop it into a bucket after full type of actions where you can 261 00:09:35,370 --> 00:09:37,920 sort of register at least in principle 262 00:09:37,920 --> 00:09:39,930 the type of effort behind the action, 263 00:09:39,930 --> 00:09:42,430 and then infants would also have the opportunity to act. 264 00:09:42,430 --> 00:09:45,340 They could perform the same actions with objects. 265 00:09:45,340 --> 00:09:47,250 Infants also for measurement purpose 266 00:09:47,250 --> 00:09:49,470 received baseline trials where we're just 267 00:09:49,470 --> 00:09:52,620 registering EEG in response to abstract images 268 00:09:52,620 --> 00:09:54,970 like a checkerboard pattern, for example. 269 00:09:54,970 --> 00:09:55,470 OK. 270 00:09:55,470 --> 00:09:57,880 So what are we interested in here? 271 00:09:57,880 --> 00:09:59,490 So, in this particular study, we were 272 00:09:59,490 --> 00:10:01,740 looking at the suppression of a particular oscillatory 273 00:10:01,740 --> 00:10:04,110 frequency called sensorimotor alpha, 274 00:10:04,110 --> 00:10:07,930 or some people call it mu attenuation. 275 00:10:07,930 --> 00:10:10,050 So we know that at rest, neurons in sensorimotor 276 00:10:10,050 --> 00:10:14,440 cortex fire spontaneously and they fire in synchrony. 277 00:10:14,440 --> 00:10:16,980 And what that means is we get these large amplitude EEG 278 00:10:16,980 --> 00:10:20,670 oscillations in the alpha frequency band. 279 00:10:20,670 --> 00:10:23,190 When the motor cortex is activated in remote motor 280 00:10:23,190 --> 00:10:25,390 cortex is activated, and that happens, of course, 281 00:10:25,390 --> 00:10:25,980 when we act. 282 00:10:25,980 --> 00:10:29,040 It also happens when we watch other people act. 283 00:10:29,040 --> 00:10:31,620 What you see is you see a suppression in sensorimotor 284 00:10:31,620 --> 00:10:33,720 alpha. 285 00:10:33,720 --> 00:10:35,730 So many people recently have been interested 286 00:10:35,730 --> 00:10:38,250 in suppression of sensorimotor alpha new attenuation 287 00:10:38,250 --> 00:10:41,130 from the perspective of looking at the mirror neuron system. 288 00:10:41,130 --> 00:10:42,910 More broadly and for our purposes, 289 00:10:42,910 --> 00:10:44,670 we're really just thinking about this 290 00:10:44,670 --> 00:10:47,520 as a measure of sensorimotor cortex activation. 291 00:10:47,520 --> 00:10:50,580 So greater suppression equals more sensorimotor cortex 292 00:10:50,580 --> 00:10:52,920 activation. 293 00:10:52,920 --> 00:10:56,250 And our question here was whether infants activation 294 00:10:56,250 --> 00:10:58,200 sensorimotor cortex wouldn't vary 295 00:10:58,200 --> 00:11:00,390 as a function of watching people lift 296 00:11:00,390 --> 00:11:01,560 blocks of different weights. 297 00:11:01,560 --> 00:11:04,140 Would you get greater activation when people 298 00:11:04,140 --> 00:11:06,270 were lifting heavier objects? 299 00:11:06,270 --> 00:11:07,694 Which would, of course, be a sign 300 00:11:07,694 --> 00:11:10,110 that infants were distinguishing between different actions 301 00:11:10,110 --> 00:11:12,651 on the basis of effort. 302 00:11:12,651 --> 00:11:13,150 OK. 303 00:11:13,150 --> 00:11:15,820 So in addition to looking at that, 304 00:11:15,820 --> 00:11:18,040 we also gave infants a group strength assessment. 305 00:11:18,040 --> 00:11:18,540 OK. 306 00:11:18,540 --> 00:11:20,220 So let me tell you a little bit about the grip strength 307 00:11:20,220 --> 00:11:22,594 measure, only because it took us several years to come up 308 00:11:22,594 --> 00:11:25,800 with this so I feel like I need to talk about it a little bit. 309 00:11:25,800 --> 00:11:28,230 So we wanted to measure infant strength, and the way 310 00:11:28,230 --> 00:11:30,150 that we did that is by measuring infants' grip strength. 311 00:11:30,150 --> 00:11:31,410 But, of course, the challenge here, 312 00:11:31,410 --> 00:11:32,610 if you're an adult, right, and you 313 00:11:32,610 --> 00:11:34,200 want to measure an adult's grip strength, 314 00:11:34,200 --> 00:11:36,120 you just get something called the dynamometer, 315 00:11:36,120 --> 00:11:38,400 you have an adult squeeze a bulb or squeeze the hand grip 316 00:11:38,400 --> 00:11:40,560 and then you get this nice force reading from that, right? 317 00:11:40,560 --> 00:11:43,040 And that all works very smoothly with adults but, of course, you 318 00:11:43,040 --> 00:11:44,040 can't just hand that to an infant 319 00:11:44,040 --> 00:11:45,539 and say, squeeze as hard as you can, 320 00:11:45,539 --> 00:11:47,220 that doesn't work, obviously. 321 00:11:47,220 --> 00:11:49,930 So what we did here is we had an experimenter who had a toy, 322 00:11:49,930 --> 00:11:51,580 the infant had the same toy. 323 00:11:51,580 --> 00:11:54,340 The experimenter would squeeze her toy, and what we hoped 324 00:11:54,340 --> 00:11:56,710 is that this would motivate infants, or lead infants, 325 00:11:56,710 --> 00:11:58,420 to squeeze their toy. 326 00:11:58,420 --> 00:12:01,540 Their toy, in contrast to the experimenter's toy, 327 00:12:01,540 --> 00:12:05,830 had both a hidden sensor embedded within the toy, which 328 00:12:05,830 --> 00:12:08,080 led to playing Old McDonald, which, of course, 329 00:12:08,080 --> 00:12:09,530 infants greatly like, right? 330 00:12:09,530 --> 00:12:11,200 They find that very enjoyable. 331 00:12:11,200 --> 00:12:14,420 And it also had a hidden pressure sensor within it. 332 00:12:14,420 --> 00:12:16,720 So we were able to get-- or to measure how 333 00:12:16,720 --> 00:12:18,584 hard infants squeezed the toy. 334 00:12:18,584 --> 00:12:20,500 Now, the trick here was we want to get infants 335 00:12:20,500 --> 00:12:21,541 strongest squeeze, right? 336 00:12:21,541 --> 00:12:23,440 So what we did is we set up our device so 337 00:12:23,440 --> 00:12:25,690 that each time the infant squeezes it, 338 00:12:25,690 --> 00:12:28,300 they have to squeeze harder to get Old McDonald to play. 339 00:12:28,300 --> 00:12:30,670 And, of course, they want Old McDonald to play, right? 340 00:12:30,670 --> 00:12:32,630 So they're motivated to keep doing that. 341 00:12:32,630 --> 00:12:34,930 So that's how we record infants' maximum grip strength. 342 00:12:34,930 --> 00:12:37,420 We like essentially keep going as long as infants will 343 00:12:37,420 --> 00:12:39,656 allow us to do that, basically. 344 00:12:39,656 --> 00:12:41,530 There are some other things that we measured. 345 00:12:41,530 --> 00:12:43,030 We measured infants weight. 346 00:12:43,030 --> 00:12:45,946 Our motivation for doing this is that an adults' strength 347 00:12:45,946 --> 00:12:47,320 and weight are highly correlated. 348 00:12:47,320 --> 00:12:49,695 They were in our sample so that kind of helps to validate 349 00:12:49,695 --> 00:12:51,130 or grip strength paradigm. 350 00:12:51,130 --> 00:12:53,860 And there were things like general motor maturity that we 351 00:12:53,860 --> 00:12:56,170 measured, gross motor skills. 352 00:12:56,170 --> 00:12:58,324 We measured how frequently infants lift blocks 353 00:12:58,324 --> 00:13:00,490 within the task, because we want a control for these 354 00:13:00,490 --> 00:13:01,210 in our analyses. 355 00:13:01,210 --> 00:13:02,626 We're wanting to look specifically 356 00:13:02,626 --> 00:13:04,910 at the effective grip strength. 357 00:13:04,910 --> 00:13:06,140 OK. 358 00:13:06,140 --> 00:13:06,640 OK. 359 00:13:06,640 --> 00:13:10,127 So let me tell you a bit-- the first thing that we looked at. 360 00:13:10,127 --> 00:13:12,210 So I'm going to show you a series of scatter plots 361 00:13:12,210 --> 00:13:14,830 that look at the relation between sensorimotor alpha 362 00:13:14,830 --> 00:13:17,620 suppression, and infant's grip strength. 363 00:13:17,620 --> 00:13:19,750 And these are plotted as a function 364 00:13:19,750 --> 00:13:21,460 of the weight of the block. 365 00:13:21,460 --> 00:13:24,847 And these are when infants are observing other people. 366 00:13:24,847 --> 00:13:27,180 So the thing to know is we're talking about suppression, 367 00:13:27,180 --> 00:13:28,763 so you're looking for negative scores. 368 00:13:28,763 --> 00:13:31,450 More negative scores mean more suppression. 369 00:13:31,450 --> 00:13:33,130 And we had a particular hypothesis 370 00:13:33,130 --> 00:13:35,920 about how this would go, or idea about how this would go. 371 00:13:35,920 --> 00:13:39,070 We thought that when the blocks were relatively light, 372 00:13:39,070 --> 00:13:41,630 grip strength would be less of a good predictor 373 00:13:41,630 --> 00:13:43,600 of sensorimotor alpha suppression. 374 00:13:43,600 --> 00:13:45,310 And the reason for thinking that is 375 00:13:45,310 --> 00:13:48,100 that whether an infant is relatively strong or relatively 376 00:13:48,100 --> 00:13:50,770 weak, they all probably have lifetime experience lifting 377 00:13:50,770 --> 00:13:52,700 relatively light objects. 378 00:13:52,700 --> 00:13:54,800 However, where strength really comes into play 379 00:13:54,800 --> 00:13:57,160 is as objects get heavier, right? 380 00:13:57,160 --> 00:13:59,410 So stronger infants, very likely, 381 00:13:59,410 --> 00:14:03,640 have a greater lifetime history of lifting heavier objects. 382 00:14:03,640 --> 00:14:05,470 So our prediction was that these two things 383 00:14:05,470 --> 00:14:09,100 would be increasingly tightly integrated as block weight goes 384 00:14:09,100 --> 00:14:10,130 up. 385 00:14:10,130 --> 00:14:12,460 And, in fact, that's exactly what we found. 386 00:14:12,460 --> 00:14:15,340 So there's weak relations when the block is light, 387 00:14:15,340 --> 00:14:17,110 when it's that heavy block-- 388 00:14:17,110 --> 00:14:19,420 we call them the heavy and the super heavy block-- 389 00:14:19,420 --> 00:14:20,590 there's a tighter relation. 390 00:14:20,590 --> 00:14:22,750 And you see the strongest relation here 391 00:14:22,750 --> 00:14:25,510 when the block is extremely heavy. 392 00:14:25,510 --> 00:14:28,030 And these analyses control for things 393 00:14:28,030 --> 00:14:30,610 like infants in task lifting experience, their weight, 394 00:14:30,610 --> 00:14:32,842 their motor development scores. 395 00:14:32,842 --> 00:14:34,300 So the next thing we wanted to know 396 00:14:34,300 --> 00:14:35,716 is we wanted to know whether there 397 00:14:35,716 --> 00:14:38,110 was any evidence that suppression of sensorimotor 398 00:14:38,110 --> 00:14:43,060 alpha would be greater in cases in which the block is heaviest 399 00:14:43,060 --> 00:14:44,710 versus the block is lightest. 400 00:14:44,710 --> 00:14:46,965 So this is really our index, or our measure, 401 00:14:46,965 --> 00:14:49,090 of whether infants are differentiating when they're 402 00:14:49,090 --> 00:14:52,000 watching other people act on objects, whether they're 403 00:14:52,000 --> 00:14:55,150 differentiating the degree of effort that goes along 404 00:14:55,150 --> 00:14:57,580 with lifting the object as a function of block weight. 405 00:14:57,580 --> 00:14:59,538 So what I'm going to show you is change scores. 406 00:14:59,538 --> 00:15:01,300 So more negative means that you're 407 00:15:01,300 --> 00:15:05,200 seeing increasing sensorimotor alpha suppression for heavy 408 00:15:05,200 --> 00:15:06,700 versus light blocks, and these are 409 00:15:06,700 --> 00:15:09,449 plotted as a function of infants' grip strength. 410 00:15:09,449 --> 00:15:11,740 So what you can see here is that for the weaker babies, 411 00:15:11,740 --> 00:15:13,781 the lower grip strength babies, you're not really 412 00:15:13,781 --> 00:15:16,060 seeing any systematic change from the latest 413 00:15:16,060 --> 00:15:17,475 block to the heaviest block. 414 00:15:17,475 --> 00:15:19,840 But you are for the stronger infants. 415 00:15:19,840 --> 00:15:22,510 So what these findings suggest to us is that the stronger 416 00:15:22,510 --> 00:15:24,912 infants appear to be differentiating these actions 417 00:15:24,912 --> 00:15:27,370 on the basis of the weight of the object that the person is 418 00:15:27,370 --> 00:15:30,950 lifting, the weaker infants aren't. 419 00:15:30,950 --> 00:15:31,450 OK. 420 00:15:31,450 --> 00:15:33,489 So what do we know from this data. 421 00:15:33,489 --> 00:15:35,280 Well, we have some evidence that activation 422 00:15:35,280 --> 00:15:37,750 of sensorimotor cortex as indexed by suppression 423 00:15:37,750 --> 00:15:40,330 of sensorimotor alpha, while babies are watching 424 00:15:40,330 --> 00:15:42,306 other people lift blocks of different weights, 425 00:15:42,306 --> 00:15:44,680 varies as the function of the weight of the block, right? 426 00:15:44,680 --> 00:15:46,360 So this might signal that infants 427 00:15:46,360 --> 00:15:49,330 are able to recognize that different actions have 428 00:15:49,330 --> 00:15:53,860 different degrees of physical effort that go along with them. 429 00:15:53,860 --> 00:15:56,440 And we also see that the ability to make this distinction 430 00:15:56,440 --> 00:15:59,800 is tied to infants own strength, their own grip strength. 431 00:15:59,800 --> 00:16:01,450 And our interpretation of this is 432 00:16:01,450 --> 00:16:04,420 that this might have to do with strength being 433 00:16:04,420 --> 00:16:06,310 a rate limiter, or a facilitator, 434 00:16:06,310 --> 00:16:08,890 or the type of experience that infants previously 435 00:16:08,890 --> 00:16:11,454 have with objects of different weights. 436 00:16:11,454 --> 00:16:13,120 And, in particular, the stronger infants 437 00:16:13,120 --> 00:16:15,580 might have more experience with lifting heavier objects. 438 00:16:15,580 --> 00:16:18,040 They might have more contrastive experience, which 439 00:16:18,040 --> 00:16:20,494 allows them to better recognize, or better differentiate, 440 00:16:20,494 --> 00:16:21,910 the degree of physical effort that 441 00:16:21,910 --> 00:16:23,680 go along with different actions when 442 00:16:23,680 --> 00:16:27,540 you're talking about lifting objects of different weight. 443 00:16:27,540 --> 00:16:28,450 OK. 444 00:16:28,450 --> 00:16:30,130 So that's part one. 445 00:16:30,130 --> 00:16:32,980 So I think what these data tell us is that in this context, 446 00:16:32,980 --> 00:16:34,660 infants have a means of registering 447 00:16:34,660 --> 00:16:35,680 effort related costs. 448 00:16:35,680 --> 00:16:38,290 I think where they go above past data is that they tell us 449 00:16:38,290 --> 00:16:41,410 that infants can do this under conditions in which they 450 00:16:41,410 --> 00:16:42,720 have minimal behavioral cues. 451 00:16:42,720 --> 00:16:44,720 So we think back to that reaching action, right? 452 00:16:44,720 --> 00:16:48,550 There's all kinds of cues that this is a costly action, right? 453 00:16:48,550 --> 00:16:51,230 There's all kinds of ways that it differs from a direct reach. 454 00:16:51,230 --> 00:16:54,020 In this situation, we're talking about actions 455 00:16:54,020 --> 00:16:57,230 that are really minimally different from one another. 456 00:16:57,230 --> 00:16:59,570 What I want to do now is I want to switch gears and talk 457 00:16:59,570 --> 00:17:01,850 about kind of the flip side of the coin. 458 00:17:01,850 --> 00:17:04,099 And that is infants use of costs and benefits, 459 00:17:04,099 --> 00:17:05,780 or reward, to guide their own behavior. 460 00:17:05,780 --> 00:17:07,550 And I'm going to be specifically focusing 461 00:17:07,550 --> 00:17:11,919 on the test case of infants prosocial behavior. 462 00:17:11,919 --> 00:17:13,460 So many of you may know this already, 463 00:17:13,460 --> 00:17:15,560 but infants are highly prosocial, right? 464 00:17:15,560 --> 00:17:17,528 There's been a lot of studies on this recently, 465 00:17:17,528 --> 00:17:19,069 and all of these studies have kind of 466 00:17:19,069 --> 00:17:20,780 come down on the conclusion that starting 467 00:17:20,780 --> 00:17:22,238 in the second year of life, infants 468 00:17:22,238 --> 00:17:24,920 will do things like help people achieve their goals, 469 00:17:24,920 --> 00:17:27,099 they will share toys or objects with other people, 470 00:17:27,099 --> 00:17:29,960 they're comfort people in distress. 471 00:17:29,960 --> 00:17:31,820 But there are questions and debates 472 00:17:31,820 --> 00:17:34,370 that are hotly contested about early prosocial development, 473 00:17:34,370 --> 00:17:38,760 and I just want to bring two of them to your attention. 474 00:17:38,760 --> 00:17:39,650 OK. 475 00:17:39,650 --> 00:17:42,560 So one question is, when does infants or children's 476 00:17:42,560 --> 00:17:46,880 prosocial behavior become selective or strategic, right? 477 00:17:46,880 --> 00:17:48,710 So we know that by preschool age, 478 00:17:48,710 --> 00:17:51,110 early school age, children's prosocial behavior 479 00:17:51,110 --> 00:17:52,841 is somewhat selective, meaning that there 480 00:17:52,841 --> 00:17:54,590 are some people, for example, that infants 481 00:17:54,590 --> 00:17:57,190 are more likely to help than others, right? 482 00:17:57,190 --> 00:17:59,990 And children are-- not infants, children-- children 483 00:17:59,990 --> 00:18:02,570 are more likely to help under situations 484 00:18:02,570 --> 00:18:06,080 where they are perhaps reputational concerns involved. 485 00:18:06,080 --> 00:18:08,510 But what we don't yet know is whether this 486 00:18:08,510 --> 00:18:10,922 is true of very early prosocial development. 487 00:18:10,922 --> 00:18:12,630 So what is the developmental course like? 488 00:18:12,630 --> 00:18:15,710 Do kids start off being selective and strategic? 489 00:18:15,710 --> 00:18:18,080 Or do they only get there over time with development? 490 00:18:18,080 --> 00:18:19,539 That's one question. 491 00:18:19,539 --> 00:18:21,080 There's another related question that 492 00:18:21,080 --> 00:18:23,420 has to do with what is the underlying motivation 493 00:18:23,420 --> 00:18:26,000 for prosocial behavior, right? 494 00:18:26,000 --> 00:18:27,890 So the kind of generous interpretation 495 00:18:27,890 --> 00:18:31,640 of infants prosocial is actions, children's prosocial action, 496 00:18:31,640 --> 00:18:34,086 is what is going on here is infants are motivated 497 00:18:34,086 --> 00:18:35,210 by empathic concern, right? 498 00:18:35,210 --> 00:18:36,751 They care about other people's needs, 499 00:18:36,751 --> 00:18:38,690 they care about other people's desires. 500 00:18:38,690 --> 00:18:40,250 And in these experimental context, 501 00:18:40,250 --> 00:18:42,830 what they're doing is they're acting to meet another person's 502 00:18:42,830 --> 00:18:45,260 needs, they're acting out of empathic concern. 503 00:18:45,260 --> 00:18:47,780 But there's also other reasons why infants, or anyone, 504 00:18:47,780 --> 00:18:49,750 for that matter, might behave prosocially, 505 00:18:49,750 --> 00:18:52,520 that might have to do with social affiliation 506 00:18:52,520 --> 00:18:55,880 biases, social motivation, that might have 507 00:18:55,880 --> 00:18:58,400 to do with wanting to see a goal being completed, 508 00:18:58,400 --> 00:19:01,490 et cetera, right? 509 00:19:01,490 --> 00:19:03,680 So one of the ways that we can start to get traction 510 00:19:03,680 --> 00:19:07,070 on these issues is by looking at the impact of various costs 511 00:19:07,070 --> 00:19:08,390 on infants' prosocial behavior. 512 00:19:08,390 --> 00:19:11,060 And somewhat surprisingly, this is not a terribly well studied 513 00:19:11,060 --> 00:19:12,870 topic as of yet. 514 00:19:12,870 --> 00:19:15,089 So there are some studies that are both with infants 515 00:19:15,089 --> 00:19:16,880 and with children, where people have looked 516 00:19:16,880 --> 00:19:20,250 at the impact of personal cost on prosocial behavior 517 00:19:20,250 --> 00:19:22,670 and, usually, the way personal costs are operationalized 518 00:19:22,670 --> 00:19:24,599 is in terms of, let's say, an infant 519 00:19:24,599 --> 00:19:27,140 is tested in a paradigm where they need to help someone else, 520 00:19:27,140 --> 00:19:28,869 or share an object with someone else. 521 00:19:28,869 --> 00:19:30,410 And they might be required to give up 522 00:19:30,410 --> 00:19:33,000 their own object versus an object that's just sitting 523 00:19:33,000 --> 00:19:34,000 there in the lab, right? 524 00:19:34,000 --> 00:19:37,900 Presumably, their own object has higher personal cost. 525 00:19:37,900 --> 00:19:41,300 Now, we don't really know when personal costs start 526 00:19:41,300 --> 00:19:42,920 to impact infants' prosocial behavior, 527 00:19:42,920 --> 00:19:44,900 because there's been a lot of mixed evidence. 528 00:19:44,900 --> 00:19:47,270 And, particularly, in infancy, there's, as of yet, 529 00:19:47,270 --> 00:19:50,490 no systematic evidence that high personal costs actually reduce 530 00:19:50,490 --> 00:19:53,174 infants' prosocial responding. 531 00:19:53,174 --> 00:19:55,340 What about the question of energetic physical effort 532 00:19:55,340 --> 00:19:56,510 related costs? 533 00:19:56,510 --> 00:19:58,890 Well, again, here, this is really an understudy topic. 534 00:19:58,890 --> 00:20:00,350 So there's one existing study that 535 00:20:00,350 --> 00:20:02,030 has looked at infants helping under kind 536 00:20:02,030 --> 00:20:05,279 of minimal physical effort cost. 537 00:20:05,279 --> 00:20:07,820 And it's a little bit hard to know what to make of that study 538 00:20:07,820 --> 00:20:09,740 because we know that infants helping behavior 539 00:20:09,740 --> 00:20:11,679 is still present under those conditions, 540 00:20:11,679 --> 00:20:13,970 we just don't really know how it compares to conditions 541 00:20:13,970 --> 00:20:15,770 where the physical costs are low. 542 00:20:18,060 --> 00:20:18,560 OK. 543 00:20:18,560 --> 00:20:21,410 So we started off by asking a really super simple question 544 00:20:21,410 --> 00:20:23,180 about infants prosocial behavior, 545 00:20:23,180 --> 00:20:26,480 and that was whether the anticipated physical effort 546 00:20:26,480 --> 00:20:28,850 that goes along with prosocial responding 547 00:20:28,850 --> 00:20:31,160 influences infants prosocial responding. 548 00:20:31,160 --> 00:20:33,710 In particular, when the effort is high, does it increase, 549 00:20:33,710 --> 00:20:36,070 or rather, decrease infants prosociality. 550 00:20:38,710 --> 00:20:39,210 OK. 551 00:20:39,210 --> 00:20:42,396 So we tested 18-month-old infants in this study. 552 00:20:42,396 --> 00:20:44,520 Start by telling you about the critical test phase, 553 00:20:44,520 --> 00:20:45,900 it was a helping task. 554 00:20:45,900 --> 00:20:48,307 An experimenter was on the opposite side of the room. 555 00:20:48,307 --> 00:20:49,890 She needs a block in order to complete 556 00:20:49,890 --> 00:20:52,140 a tower that she's building. 557 00:20:52,140 --> 00:20:53,981 What happens before that is all infants 558 00:20:53,981 --> 00:20:55,230 take part in a training phase. 559 00:20:55,230 --> 00:20:56,813 They're faced with these vinyl blocks. 560 00:20:56,813 --> 00:20:58,560 You'll see a video clip in a moment. 561 00:20:58,560 --> 00:21:00,000 And these vinyl clocks have-- 562 00:21:00,000 --> 00:21:03,072 blocks have been rigged by us so that they range in weight. 563 00:21:03,072 --> 00:21:05,030 There's five of them, they're different colors, 564 00:21:05,030 --> 00:21:06,569 so infants can keep track of them. 565 00:21:06,569 --> 00:21:08,610 During training, what happens is the experimenter 566 00:21:08,610 --> 00:21:10,320 plays a game with an infant where 567 00:21:10,320 --> 00:21:13,860 they get them to drop each block into a bucket. 568 00:21:13,860 --> 00:21:16,590 Babies like to do that, it makes a cool noise, right? 569 00:21:16,590 --> 00:21:19,090 And, really, this training phase serves two purposes. 570 00:21:19,090 --> 00:21:20,580 The first purpose that it serves is 571 00:21:20,580 --> 00:21:23,460 we want infants to learn how much each block weighs. 572 00:21:23,460 --> 00:21:24,960 The second purpose that it serves 573 00:21:24,960 --> 00:21:27,000 is we want to be able to record what 574 00:21:27,000 --> 00:21:30,000 is the heaviest block that infants are capable of lifting. 575 00:21:30,000 --> 00:21:31,350 All right. 576 00:21:31,350 --> 00:21:32,850 In the test phase, as I told you, 577 00:21:32,850 --> 00:21:34,680 the experimenter's on the opposite side of the room, 578 00:21:34,680 --> 00:21:36,120 she's building a block tower, she 579 00:21:36,120 --> 00:21:38,072 needs a block to complete it. 580 00:21:38,072 --> 00:21:40,530 There's a single target block available to infants and what 581 00:21:40,530 --> 00:21:42,510 varies between our two conditions 582 00:21:42,510 --> 00:21:43,920 is the weight of that block. 583 00:21:43,920 --> 00:21:46,590 So for half of the babies, the lightest block of the training 584 00:21:46,590 --> 00:21:48,169 blocks is left behind. 585 00:21:48,169 --> 00:21:49,710 And for the other half of the babies, 586 00:21:49,710 --> 00:21:52,080 the heaviest block that infants are capable of lifting 587 00:21:52,080 --> 00:21:53,400 has been left behind. 588 00:21:53,400 --> 00:21:55,226 So we're contrasting effort here in terms 589 00:21:55,226 --> 00:21:56,850 of the weight of the block that infants 590 00:21:56,850 --> 00:22:01,960 have to carry across the room to help the experimenter. 591 00:22:01,960 --> 00:22:04,050 So we're looking at infants block retrievals. 592 00:22:04,050 --> 00:22:06,570 The other thing that we recorded was a parent report 593 00:22:06,570 --> 00:22:07,900 of infants walking experience. 594 00:22:07,900 --> 00:22:10,800 So these are 18-month-old infants, they can all walk. 595 00:22:10,800 --> 00:22:12,990 On average, they've been walking for six months 596 00:22:12,990 --> 00:22:14,970 so they're all experienced walkers. 597 00:22:14,970 --> 00:22:16,470 But there's individual variability 598 00:22:16,470 --> 00:22:19,290 in terms of how long they've been walking for. 599 00:22:19,290 --> 00:22:20,470 So why was this important? 600 00:22:20,470 --> 00:22:21,750 Well, here was our underlying logic. 601 00:22:21,750 --> 00:22:23,833 Imagine that you and a friend are going on a hike, 602 00:22:23,833 --> 00:22:26,550 you're both equally strong, you can both lift 60 pounds. 603 00:22:26,550 --> 00:22:28,260 But your friend is an expert hiker 604 00:22:28,260 --> 00:22:29,972 and you're a novice hiker, right? 605 00:22:29,972 --> 00:22:32,430 And you both have to carry a 60 pound backpack up the hill. 606 00:22:32,430 --> 00:22:35,244 Well, despite the fact that you might both be equally strong, 607 00:22:35,244 --> 00:22:36,660 if you're the novice hiker, that's 608 00:22:36,660 --> 00:22:38,451 probably going to be more effortful for you 609 00:22:38,451 --> 00:22:40,830 to get that backpack up the hill than it is going to be 610 00:22:40,830 --> 00:22:42,850 for your friend or your buddy. 611 00:22:42,850 --> 00:22:44,700 So we had a particular prediction 612 00:22:44,700 --> 00:22:48,060 that what we would see is a relationship between parent 613 00:22:48,060 --> 00:22:51,120 reporter walking experience, and infants likelihood do this-- 614 00:22:51,120 --> 00:22:53,160 likelihood to help the experimenter by carrying 615 00:22:53,160 --> 00:22:56,040 the block across the room, and that this would be selective, 616 00:22:56,040 --> 00:23:00,780 or at least stronger, for the high effort condition. 617 00:23:00,780 --> 00:23:02,070 OK. 618 00:23:02,070 --> 00:23:04,140 So let me show you a couple little video clips 619 00:23:04,140 --> 00:23:07,064 here so you can get a flavor of the procedure. 620 00:23:07,064 --> 00:23:08,730 This is just showing you the test phase, 621 00:23:08,730 --> 00:23:10,919 so it's exerted from the test phase. 622 00:23:10,919 --> 00:23:12,960 There's one thing I want to explain a little bit. 623 00:23:12,960 --> 00:23:17,765 So you can see up here there's this striped bucket here. 624 00:23:17,765 --> 00:23:19,140 And the reason that we have there 625 00:23:19,140 --> 00:23:21,514 is-- that there is because we want the experimenter to be 626 00:23:21,514 --> 00:23:23,670 unaware of the target block that is left behind, 627 00:23:23,670 --> 00:23:25,860 so they're naive to the infant's condition. 628 00:23:25,860 --> 00:23:27,780 It looks like from the infants' perspective that they can see 629 00:23:27,780 --> 00:23:29,180 the target block, but they actually can't. 630 00:23:29,180 --> 00:23:30,420 They don't know if they're in the high or low effort 631 00:23:30,420 --> 00:23:31,260 condition. 632 00:23:31,260 --> 00:23:34,440 So this is the baby who is tested in the low effort 633 00:23:34,440 --> 00:23:36,952 condition. 634 00:23:36,952 --> 00:23:37,618 [VIDEO PLAYBACK] 635 00:23:37,618 --> 00:23:40,500 I'm going to use these blocks to make a tower. 636 00:23:40,500 --> 00:23:42,010 These blocks can go here. 637 00:23:45,020 --> 00:23:47,976 This one can go here. 638 00:23:47,976 --> 00:23:50,560 And this block can go-- 639 00:23:50,560 --> 00:23:53,140 oh, no. 640 00:23:53,140 --> 00:23:58,010 Oh, no, I'm missing the block I need to finish my tower. 641 00:23:58,010 --> 00:23:59,994 I'm missing my block. 642 00:23:59,994 --> 00:24:02,994 Ah, oh, there it is, Joelle look. 643 00:24:02,994 --> 00:24:06,140 The block got moved on your blanket. 644 00:24:06,140 --> 00:24:09,048 Can you bring me the blocks so I can finish my tower? 645 00:24:14,327 --> 00:24:14,910 [END PLAYBACK] 646 00:24:14,910 --> 00:24:15,459 All right. 647 00:24:15,459 --> 00:24:17,000 Sorry, we exerted a little bit early. 648 00:24:17,000 --> 00:24:18,666 He goes over and he gives her the block. 649 00:24:18,666 --> 00:24:19,410 OK. 650 00:24:19,410 --> 00:24:19,910 OK. 651 00:24:19,910 --> 00:24:21,890 Now let's watch a baby in the high effort condition. 652 00:24:21,890 --> 00:24:23,840 Remember, the only difference between these two conditions 653 00:24:23,840 --> 00:24:26,210 is the weight of the block that's been left behind. 654 00:24:26,210 --> 00:24:27,412 OK. 655 00:24:27,412 --> 00:24:28,344 [VIDEO PLAYBACK] 656 00:24:28,344 --> 00:24:32,275 I'm going to use these blocks to make a tower These blocks can 657 00:24:32,275 --> 00:24:34,430 go here. 658 00:24:34,430 --> 00:24:37,150 This one can go here. 659 00:24:37,150 --> 00:24:39,548 And this one can go-- 660 00:24:39,548 --> 00:24:41,908 oh, no. 661 00:24:41,908 --> 00:24:46,462 Oh, no, I'm missing the block I need to finish my tower. 662 00:24:46,462 --> 00:24:48,872 I'm missing my block. 663 00:24:48,872 --> 00:24:50,318 Ah, oh. 664 00:24:50,318 --> 00:24:51,764 There it is, Rose. 665 00:24:51,764 --> 00:24:54,360 The block got left on your blanket. 666 00:24:54,360 --> 00:24:57,140 Can you bring me the block so I can finish my tower? 667 00:25:00,125 --> 00:25:07,035 [LAUGHTER] Can you bring me the block? 668 00:25:11,936 --> 00:25:16,972 Rose, can you bring me the block so I can finish my tower? 669 00:25:16,972 --> 00:25:17,472 No. 670 00:25:24,307 --> 00:25:24,890 [END PLAYBACK] 671 00:25:24,890 --> 00:25:26,430 So it's a little hard to hear what she was saying, 672 00:25:26,430 --> 00:25:28,700 but if you couldn't hear it, she was saying, no, thank you. 673 00:25:28,700 --> 00:25:29,240 So she said, no. 674 00:25:29,240 --> 00:25:29,770 No, thank you. 675 00:25:29,770 --> 00:25:30,353 No, thank you. 676 00:25:30,353 --> 00:25:31,760 OK. 677 00:25:31,760 --> 00:25:34,470 So that's a-- pretty illustrative of the procedure. 678 00:25:34,470 --> 00:25:34,970 OK. 679 00:25:34,970 --> 00:25:35,890 So what did we find? 680 00:25:35,890 --> 00:25:38,161 So here's infants' rates of helping in the low effort 681 00:25:38,161 --> 00:25:38,660 condition. 682 00:25:38,660 --> 00:25:40,880 In the high effort condition what you can see. 683 00:25:40,880 --> 00:25:42,440 So infants help much more frequently 684 00:25:42,440 --> 00:25:45,055 in the low effort condition than in a high effort condition. 685 00:25:45,055 --> 00:25:46,430 Here's what we found with respect 686 00:25:46,430 --> 00:25:47,900 to infants' walking experience. 687 00:25:47,900 --> 00:25:50,930 A walking experience, how long an infant has been walking 688 00:25:50,930 --> 00:25:53,390 predicts infants' likelihood of helping in the high effort 689 00:25:53,390 --> 00:25:54,470 condition. 690 00:25:54,470 --> 00:25:57,115 And what this tells us is that for each month 691 00:25:57,115 --> 00:25:58,490 of additional walking experience, 692 00:25:58,490 --> 00:26:00,950 infants are twice as likely to help. 693 00:26:00,950 --> 00:26:03,170 Now, what we can see here is that infants 694 00:26:03,170 --> 00:26:05,690 are less likely to help under high effort conditions, right? 695 00:26:05,690 --> 00:26:07,910 So infants prosocial behavior is influenced 696 00:26:07,910 --> 00:26:11,100 by the effort related costs of prosocial responding. 697 00:26:11,100 --> 00:26:14,430 And a critic, I guess, could say, 698 00:26:14,430 --> 00:26:16,820 well, maybe it's that-- it's not that infants 699 00:26:16,820 --> 00:26:18,920 are going by the effort, it's maybe 700 00:26:18,920 --> 00:26:21,600 that they're not able to help in the high effort condition. 701 00:26:21,600 --> 00:26:23,990 We don't think that that's the case, because infants have 702 00:26:23,990 --> 00:26:26,960 given us evidence that they're capable of lifting that block, 703 00:26:26,960 --> 00:26:27,480 right? 704 00:26:27,480 --> 00:26:29,854 That they're later-- later tested with in the high effort 705 00:26:29,854 --> 00:26:30,395 condition. 706 00:26:30,395 --> 00:26:31,895 But the next condition I'll show you 707 00:26:31,895 --> 00:26:35,250 will also kind of speak to that. 708 00:26:35,250 --> 00:26:37,550 And the important-- another important thing 709 00:26:37,550 --> 00:26:40,150 to recognize here is that infants 710 00:26:40,150 --> 00:26:43,280 seem to be recognizing these costs at an objective level. 711 00:26:43,280 --> 00:26:45,500 I think Laura called this in her talk an agent 712 00:26:45,500 --> 00:26:46,700 independent level, right? 713 00:26:46,700 --> 00:26:49,280 As a function of the circumstances of the situation, 714 00:26:49,280 --> 00:26:50,240 right? 715 00:26:50,240 --> 00:26:52,520 And they're also recognizing costs 716 00:26:52,520 --> 00:26:54,200 that at a more subjective level in terms 717 00:26:54,200 --> 00:26:56,000 of their own capabilities and how that 718 00:26:56,000 --> 00:26:57,440 influences the particular cost. 719 00:26:57,440 --> 00:26:59,690 In this case, it's their amount of walking experience, 720 00:26:59,690 --> 00:27:02,450 how expert a walker they are. 721 00:27:02,450 --> 00:27:04,850 OK. 722 00:27:04,850 --> 00:27:07,040 So what we wanted to do next is to find out 723 00:27:07,040 --> 00:27:09,230 whether if when infants are presented 724 00:27:09,230 --> 00:27:11,277 with these high effortful helping situations, 725 00:27:11,277 --> 00:27:12,860 whether infants helping behavior would 726 00:27:12,860 --> 00:27:16,160 vary as a function of the motivational benefits 727 00:27:16,160 --> 00:27:18,900 of prosocial responding. 728 00:27:18,900 --> 00:27:20,930 Now, it's been pretty firmly established 729 00:27:20,930 --> 00:27:23,180 that early prosocial responding appears to be 730 00:27:23,180 --> 00:27:24,750 immune to extrinsic rewards. 731 00:27:24,750 --> 00:27:26,270 So what that means is if you test 732 00:27:26,270 --> 00:27:27,936 a baby in one of these helping paradigms 733 00:27:27,936 --> 00:27:29,889 and you say, good job, way to go, good job. 734 00:27:29,889 --> 00:27:31,430 That's actually not going to increase 735 00:27:31,430 --> 00:27:32,846 their subsequent helping behavior. 736 00:27:32,846 --> 00:27:35,701 If anything, it will decrease it. 737 00:27:35,701 --> 00:27:38,360 But that doesn't mean that more intrinsic rewards 738 00:27:38,360 --> 00:27:39,860 don't influence how infants perform 739 00:27:39,860 --> 00:27:40,943 on these particular tasks. 740 00:27:44,030 --> 00:27:46,820 We know from some prior work that infants by this age 741 00:27:46,820 --> 00:27:49,250 have certain affiliated biases, right? 742 00:27:49,250 --> 00:27:51,200 They have biases for individuals who 743 00:27:51,200 --> 00:27:53,300 share their preferences, who share the-- 744 00:27:53,300 --> 00:27:55,290 who like the same things that the infant likes. 745 00:27:55,290 --> 00:27:57,140 They prefer to play with those people who-- 746 00:27:57,140 --> 00:27:59,690 than people who don't like the same thing that they like. 747 00:27:59,690 --> 00:28:03,110 And they also have-- possess affiliated biases for people 748 00:28:03,110 --> 00:28:03,860 who could be-- 749 00:28:03,860 --> 00:28:06,716 said to share sort of in-group member characteristics, right? 750 00:28:06,716 --> 00:28:08,090 So infants, like people who speak 751 00:28:08,090 --> 00:28:09,464 in native-- their native language 752 00:28:09,464 --> 00:28:12,200 over a nonnative language speaker. 753 00:28:12,200 --> 00:28:13,970 And, of course, these affiliated biases 754 00:28:13,970 --> 00:28:16,250 might have important functional consequences, right? 755 00:28:16,250 --> 00:28:19,070 They might be important for cultural learning. 756 00:28:22,840 --> 00:28:25,380 So what we wanted to know in this next study 757 00:28:25,380 --> 00:28:28,800 is whether we could kind of push around these intrinsic benefits 758 00:28:28,800 --> 00:28:30,870 for infants to see if their behavior would 759 00:28:30,870 --> 00:28:33,599 change under these high effort helping conditions. 760 00:28:33,599 --> 00:28:35,640 The way that we did this in this particular study 761 00:28:35,640 --> 00:28:40,530 is prior to the test procedure, the helping task, 762 00:28:40,530 --> 00:28:42,750 we had infants take part in this little task 763 00:28:42,750 --> 00:28:44,070 where they were given one-- 764 00:28:44,070 --> 00:28:44,580 two toys. 765 00:28:44,580 --> 00:28:45,840 They could choose between the two toys. 766 00:28:45,840 --> 00:28:47,190 This happened on three different trials, 767 00:28:47,190 --> 00:28:48,394 different toys each trial. 768 00:28:48,394 --> 00:28:49,560 Infants would make a choice. 769 00:28:49,560 --> 00:28:53,010 And then the experimenter would subsequently 770 00:28:53,010 --> 00:28:56,010 show that she liked one toy and disliked the other toy. 771 00:28:56,010 --> 00:28:57,720 And the really simple manipulation 772 00:28:57,720 --> 00:28:59,310 between these two different conditions 773 00:28:59,310 --> 00:29:02,400 was whether the experimenter liked the same toy as the baby, 774 00:29:02,400 --> 00:29:04,050 or whether she liked the other toy. 775 00:29:04,050 --> 00:29:06,420 So did she share the infant's preferences, 776 00:29:06,420 --> 00:29:08,706 or did she oppose their preferences, right? 777 00:29:08,706 --> 00:29:10,330 And we would think in terms of the data 778 00:29:10,330 --> 00:29:11,910 on infants affiliative biases, that they 779 00:29:11,910 --> 00:29:13,451 would prefer to interact with someone 780 00:29:13,451 --> 00:29:16,320 who shares their preferences. 781 00:29:16,320 --> 00:29:18,570 Infants took part in the same helping task 782 00:29:18,570 --> 00:29:20,340 as they did in the first experiment. 783 00:29:20,340 --> 00:29:23,160 To streamline the procedure, we used the medium block weight 784 00:29:23,160 --> 00:29:26,174 that infants have been capable of lifting in the first study. 785 00:29:26,174 --> 00:29:28,590 The other thing that we did is we added a post-test phase. 786 00:29:28,590 --> 00:29:31,380 So we excluded any infants who were not 787 00:29:31,380 --> 00:29:34,350 capable in the post-test of lifting the target block 788 00:29:34,350 --> 00:29:35,490 or a heavier block, right? 789 00:29:35,490 --> 00:29:38,370 So we know for all of these infants in the sample 790 00:29:38,370 --> 00:29:39,690 that they can lift the block. 791 00:29:39,690 --> 00:29:43,084 The question is, do they help the experimenter. 792 00:29:46,491 --> 00:29:46,990 OK. 793 00:29:46,990 --> 00:29:48,760 So we again looked at infants' helping behavior, 794 00:29:48,760 --> 00:29:50,540 we looked at their walking experience. 795 00:29:50,540 --> 00:29:51,850 The other thing that we did in the study 796 00:29:51,850 --> 00:29:54,280 is we looked at infants helping as a function of the response 797 00:29:54,280 --> 00:29:54,780 period. 798 00:29:54,780 --> 00:29:56,435 Whether helping occurred in the-- 799 00:29:56,435 --> 00:29:58,810 rates of helping in the first half of the response period 800 00:29:58,810 --> 00:30:01,630 versus the rates of helping overall in the response period. 801 00:30:01,630 --> 00:30:03,220 And our motivation for doing this 802 00:30:03,220 --> 00:30:05,320 is that we thought that if there are differences 803 00:30:05,320 --> 00:30:06,819 in the degree of motivation to help, 804 00:30:06,819 --> 00:30:09,700 you might see early differences in the response period, right? 805 00:30:09,700 --> 00:30:11,620 So early on, infants might differentiate 806 00:30:11,620 --> 00:30:13,100 across the conditions. 807 00:30:13,100 --> 00:30:15,410 But these might attenuate over time. 808 00:30:15,410 --> 00:30:17,560 One thing I forgot to mention is that in the course 809 00:30:17,560 --> 00:30:19,540 of the response period, infants receive 810 00:30:19,540 --> 00:30:23,260 prompts at certain intervals in order to say, 811 00:30:23,260 --> 00:30:24,910 can you get me the block, right? 812 00:30:24,910 --> 00:30:26,590 So the question is with these prompts 813 00:30:26,590 --> 00:30:30,840 will any early differences that we see attenuate over time? 814 00:30:30,840 --> 00:30:31,377 OK. 815 00:30:31,377 --> 00:30:32,460 So here's what we can see. 816 00:30:32,460 --> 00:30:33,850 This is the first half of the response period. 817 00:30:33,850 --> 00:30:35,600 Infants in the shared preference condition 818 00:30:35,600 --> 00:30:38,530 are significantly more likely to help the experimenter 819 00:30:38,530 --> 00:30:41,350 than infants in the nonshared preference condition, right? 820 00:30:41,350 --> 00:30:43,690 So when there are intrinsic rewards associated 821 00:30:43,690 --> 00:30:45,310 with engaging in high effort behavior, 822 00:30:45,310 --> 00:30:47,670 infants are more likely to help the experimenter. 823 00:30:47,670 --> 00:30:49,450 And the other thing that we saw is 824 00:30:49,450 --> 00:30:51,970 that infants walking experience significantly 825 00:30:51,970 --> 00:30:55,870 predicts helping behavior in the nonshared preference condition. 826 00:30:55,870 --> 00:30:58,630 So when the motivational benefits are low, 827 00:30:58,630 --> 00:31:01,990 these subjective costs seem to exert a stronger-- 828 00:31:01,990 --> 00:31:04,980 a stronger role, have a stronger predictive value, 829 00:31:04,980 --> 00:31:07,819 than when the motivational consequences-- or, sorry, 830 00:31:07,819 --> 00:31:09,110 motivational benefits are high. 831 00:31:11,521 --> 00:31:14,020 And then here, this just shows you infants' helping behavior 832 00:31:14,020 --> 00:31:16,180 but, now, as a function of the overall response period. 833 00:31:16,180 --> 00:31:18,180 You can see they're still numerically different, 834 00:31:18,180 --> 00:31:19,870 but they start to come together, right? 835 00:31:19,870 --> 00:31:21,520 So the differences are really driven 836 00:31:21,520 --> 00:31:23,860 by what's happening early in the response period. 837 00:31:27,440 --> 00:31:28,087 OK. 838 00:31:28,087 --> 00:31:30,170 So these findings suggest that infants willingness 839 00:31:30,170 --> 00:31:31,730 to engage in high effort-- 840 00:31:31,730 --> 00:31:33,680 high cost helping is motivated or affected 841 00:31:33,680 --> 00:31:35,867 by intrinsic motivational factors. 842 00:31:35,867 --> 00:31:38,450 Infants are more likely to carry a heavy block to help someone 843 00:31:38,450 --> 00:31:39,740 who shares their preference. 844 00:31:39,740 --> 00:31:41,156 One thing I want to point out here 845 00:31:41,156 --> 00:31:43,426 is that these findings help us sort of 846 00:31:43,426 --> 00:31:45,800 interpret what's going on in the first experiment, right? 847 00:31:45,800 --> 00:31:48,140 If the first experiment was explained by the fact 848 00:31:48,140 --> 00:31:50,656 that it's a lack of ability versus a lack of effort, 849 00:31:50,656 --> 00:31:52,280 we shouldn't get these findings, right? 850 00:31:52,280 --> 00:31:54,620 Because the effort is equivalent across these two conditions 851 00:31:54,620 --> 00:31:55,119 here. 852 00:31:55,119 --> 00:32:00,625 And what simply varies are the kind of motivational benefits. 853 00:32:00,625 --> 00:32:01,432 OK. 854 00:32:01,432 --> 00:32:03,140 So, now, I want to tell you about a study 855 00:32:03,140 --> 00:32:05,885 that we're just in the middle of conducting. 856 00:32:05,885 --> 00:32:07,760 I think it's really exciting and interesting. 857 00:32:07,760 --> 00:32:08,820 I'd be curious to get your thoughts. 858 00:32:08,820 --> 00:32:10,760 So we're literally mid data collection, 859 00:32:10,760 --> 00:32:12,590 but I think I have enough data to tell you 860 00:32:12,590 --> 00:32:15,110 what's going on so far. 861 00:32:15,110 --> 00:32:17,630 So, now, we're trying to expand the scope of benefits 862 00:32:17,630 --> 00:32:19,400 that we're looking at, right? 863 00:32:19,400 --> 00:32:21,720 And as we sort of alluded to earlier, 864 00:32:21,720 --> 00:32:23,530 we don't-- really don't know as of yet, 865 00:32:23,530 --> 00:32:25,940 or we don't know very much, about what cost counts 866 00:32:25,940 --> 00:32:27,970 as a cost and a benefit for infants, right? 867 00:32:27,970 --> 00:32:29,345 That's something that we actually 868 00:32:29,345 --> 00:32:31,509 have to figure out to determine empirically. 869 00:32:31,509 --> 00:32:33,050 There's been some recent studies that 870 00:32:33,050 --> 00:32:35,510 have shown that three- and four-year-olds, perhaps 871 00:32:35,510 --> 00:32:38,540 paradoxically, when they're tested in sharing tasks, 872 00:32:38,540 --> 00:32:41,450 are more likely to share with a rich recipient 873 00:32:41,450 --> 00:32:43,460 than a poor recipient, right? 874 00:32:43,460 --> 00:32:45,740 And that is paradoxical in the sense that, of course, 875 00:32:45,740 --> 00:32:49,160 the rich recipient has less of a need than the poor recipient. 876 00:32:49,160 --> 00:32:52,550 But, perhaps, unsurprising in the sense 877 00:32:52,550 --> 00:32:54,470 that there's something self-serving, right, 878 00:32:54,470 --> 00:32:56,810 like it might be in your self-interest to affiliate 879 00:32:56,810 --> 00:32:59,018 with people who have a lot of resources versus people 880 00:32:59,018 --> 00:33:00,230 who have few resources. 881 00:33:00,230 --> 00:33:03,080 In our study, what we did, is before infants got the helping 882 00:33:03,080 --> 00:33:05,660 task, we demonstrated to them that one individual 883 00:33:05,660 --> 00:33:08,420 had more resources than the other individual. 884 00:33:08,420 --> 00:33:09,890 It's a really simple manipulation. 885 00:33:09,890 --> 00:33:11,690 What they did is they saw two individuals are 886 00:33:11,690 --> 00:33:12,481 sitting at a table. 887 00:33:12,481 --> 00:33:14,810 They both had these like transparent fish bowl looking 888 00:33:14,810 --> 00:33:18,110 balls, and on each trial they have different goods 889 00:33:18,110 --> 00:33:19,520 in the fish bowls. 890 00:33:19,520 --> 00:33:23,030 So what happens is that one individual always 891 00:33:23,030 --> 00:33:24,297 has lots of stuff, right? 892 00:33:24,297 --> 00:33:26,380 On one trial it's animal crackers, the other trial 893 00:33:26,380 --> 00:33:27,650 it's these cool little balls. 894 00:33:27,650 --> 00:33:31,280 The third trial it's these cool, flashing little blingy rings. 895 00:33:31,280 --> 00:33:33,800 And the other person has very few. 896 00:33:33,800 --> 00:33:35,930 But they both do exactly the same thing 897 00:33:35,930 --> 00:33:36,980 during this first phase. 898 00:33:36,980 --> 00:33:38,530 What they do is they take turns-- 899 00:33:38,530 --> 00:33:40,280 we counterbalance everything, of course-- 900 00:33:40,280 --> 00:33:42,260 they pull out three objects one at a time 901 00:33:42,260 --> 00:33:46,700 and, they say, hey, baby, look at all my toys, right? 902 00:33:46,700 --> 00:33:49,390 So they're both doing the same thing, exactly the same thing. 903 00:33:49,390 --> 00:33:53,690 What differs is the kind of resource contacts, right? 904 00:33:53,690 --> 00:33:55,050 One of them has a lot of stuff. 905 00:33:55,050 --> 00:33:57,240 One of them only has three things, right? 906 00:33:57,240 --> 00:33:58,670 And we do that on repeated trials, 907 00:33:58,670 --> 00:34:00,000 because we're trying to give babies 908 00:34:00,000 --> 00:34:02,240 the impression that, generally, this person has more 909 00:34:02,240 --> 00:34:03,945 stuff than the other person. 910 00:34:03,945 --> 00:34:05,300 OK. 911 00:34:05,300 --> 00:34:07,197 So then we test infants in the helping task. 912 00:34:07,197 --> 00:34:09,530 This helping task is a little bit different than the one 913 00:34:09,530 --> 00:34:11,196 I just told you about, because now we're 914 00:34:11,196 --> 00:34:13,500 pitting these two experimenters against one another. 915 00:34:13,500 --> 00:34:16,280 The experimenters in the helping task have equivalent need. 916 00:34:16,280 --> 00:34:18,409 They both, like Miranda was doing earlier, 917 00:34:18,409 --> 00:34:19,701 are building this tower, right? 918 00:34:19,701 --> 00:34:21,450 They're missing a block, they need a block 919 00:34:21,450 --> 00:34:22,850 to complete their tower, right? 920 00:34:22,850 --> 00:34:24,020 The only thing that differentiates 921 00:34:24,020 --> 00:34:25,730 the experimenters is what happened previously. 922 00:34:25,730 --> 00:34:27,688 One person had a lot of stuff, the other person 923 00:34:27,688 --> 00:34:29,840 didn't have very much stuff. 924 00:34:29,840 --> 00:34:32,239 And the other thing that we're manipulating here 925 00:34:32,239 --> 00:34:35,420 is whether the infant has to engage 926 00:34:35,420 --> 00:34:39,830 in equally effortful actions to help the two experimenters, 927 00:34:39,830 --> 00:34:42,560 or whether helping one of the experimenters 928 00:34:42,560 --> 00:34:44,000 is more effortful. 929 00:34:44,000 --> 00:34:45,920 And the way that we've operationalized this so 930 00:34:45,920 --> 00:34:50,960 far in this study is by varying how long the baby has to walk. 931 00:34:50,960 --> 00:34:53,600 So, in one case, the person is within a few feet, 932 00:34:53,600 --> 00:34:55,440 in the other case, they're across the room. 933 00:34:55,440 --> 00:34:57,560 OK. 934 00:34:57,560 --> 00:34:59,990 So let me show you the data, first, for the equal effort 935 00:34:59,990 --> 00:35:00,580 condition. 936 00:35:00,580 --> 00:35:02,660 So these are-- this is-- 937 00:35:02,660 --> 00:35:06,410 what this graph shows you is who the baby is helping. 938 00:35:06,410 --> 00:35:09,950 And what you can see here is when effort is equivalent, 939 00:35:09,950 --> 00:35:12,290 infants are systematically helping the person 940 00:35:12,290 --> 00:35:13,490 who has more resources. 941 00:35:13,490 --> 00:35:16,346 They're helping the rich experimenter, right? 942 00:35:16,346 --> 00:35:17,720 So now the question becomes, what 943 00:35:17,720 --> 00:35:19,504 happens in cases of unequal effort? 944 00:35:19,504 --> 00:35:21,170 And as I said, this data is still coming 945 00:35:21,170 --> 00:35:23,086 and we're still testing this, so the condition 946 00:35:23,086 --> 00:35:26,150 that we started with, given that we have this initial pattern, 947 00:35:26,150 --> 00:35:28,760 is the condition where the rich experimenter is the one you 948 00:35:28,760 --> 00:35:30,021 have to walk a long way to. 949 00:35:30,021 --> 00:35:31,520 And the poor experimenter is the one 950 00:35:31,520 --> 00:35:34,432 you have to walk a short way to. 951 00:35:34,432 --> 00:35:35,390 And here's what we see. 952 00:35:35,390 --> 00:35:37,680 It flips. 953 00:35:37,680 --> 00:35:42,080 So I think what this suggests is that infants are both weighing 954 00:35:42,080 --> 00:35:45,080 the costs of the action they have to perform, 955 00:35:45,080 --> 00:35:48,770 and the intrinsic motivational benefits as defined 956 00:35:48,770 --> 00:35:50,240 by these sort of things that might 957 00:35:50,240 --> 00:35:52,370 be important for social affiliation. 958 00:35:55,050 --> 00:35:55,550 OK. 959 00:35:55,550 --> 00:35:57,008 So what implications does this have 960 00:35:57,008 --> 00:35:59,182 for infants' prosocial behavior? 961 00:35:59,182 --> 00:36:00,890 Well, it suggests that it may be the case 962 00:36:00,890 --> 00:36:02,750 that cost benefit analyses underlie 963 00:36:02,750 --> 00:36:04,070 infants prosocial behavior. 964 00:36:04,070 --> 00:36:06,890 In particular, their helping behavior. 965 00:36:06,890 --> 00:36:09,304 And I also want to take us back to two of the questions 966 00:36:09,304 --> 00:36:10,220 that I raised earlier. 967 00:36:10,220 --> 00:36:12,680 One was about the selective nature 968 00:36:12,680 --> 00:36:15,830 of early prosocial behavior, the strategic nature. 969 00:36:15,830 --> 00:36:19,160 And the other was about the underlying motivation. 970 00:36:19,160 --> 00:36:22,020 So think in terms of the selective strategic question, 971 00:36:22,020 --> 00:36:25,400 on the one hand, we can say, fairly early on at 18 months, 972 00:36:25,400 --> 00:36:28,340 infants' prosocial behavior is strategic in the sense 973 00:36:28,340 --> 00:36:30,350 that what they seem to be doing is 974 00:36:30,350 --> 00:36:33,330 minimizing costs and maximizing motivational benefits. 975 00:36:36,510 --> 00:36:38,300 And in terms of the motivation, I 976 00:36:38,300 --> 00:36:39,860 think what these findings tell us, 977 00:36:39,860 --> 00:36:42,170 and this is not to say that infants are never motivated 978 00:36:42,170 --> 00:36:43,586 by empathic concern, they're never 979 00:36:43,586 --> 00:36:45,270 motivated by other people's needs, 980 00:36:45,270 --> 00:36:47,620 but there are other things that come into play here. 981 00:36:47,620 --> 00:36:50,120 So infants' underlying motivation to help 982 00:36:50,120 --> 00:36:52,910 is influenced by a tendency to want to affiliate 983 00:36:52,910 --> 00:36:56,750 with particular individuals. 984 00:36:56,750 --> 00:36:57,377 OK. 985 00:36:57,377 --> 00:36:59,960 So I told you a little bit about infants registration of costs 986 00:36:59,960 --> 00:37:02,757 in the actions of other people, their use of costs and benefits 987 00:37:02,757 --> 00:37:04,340 to guide their own prosocial behavior. 988 00:37:04,340 --> 00:37:08,030 I just want to close by kind of raising some questions that I 989 00:37:08,030 --> 00:37:11,010 think we should be interested in pursuing in the future. 990 00:37:11,010 --> 00:37:11,510 OK. 991 00:37:11,510 --> 00:37:12,920 So this came up earlier, right? 992 00:37:12,920 --> 00:37:14,545 So one thing that we have to understand 993 00:37:14,545 --> 00:37:16,040 to understand infants' behavior is 994 00:37:16,040 --> 00:37:18,200 to understand what acts as a cost for infants 995 00:37:18,200 --> 00:37:19,984 and what acts as a benefit for infants. 996 00:37:19,984 --> 00:37:22,400 And I think the thing that's really important to point out 997 00:37:22,400 --> 00:37:26,000 here is it won't necessarily be what we think as adults, right? 998 00:37:26,000 --> 00:37:28,322 It won't be intuitive to us, right? 999 00:37:28,322 --> 00:37:29,780 And the classic example that we can 1000 00:37:29,780 --> 00:37:32,720 think about is, you know, you buy your child this toy, 1001 00:37:32,720 --> 00:37:34,280 you bring it home from the store, 1002 00:37:34,280 --> 00:37:36,830 you're so excited to give your child this cool snazzy toy, 1003 00:37:36,830 --> 00:37:39,530 and all they want to do is play with the box, right? 1004 00:37:39,530 --> 00:37:42,414 So what that shows us is we're not good models, necessarily. 1005 00:37:42,414 --> 00:37:44,330 We have to kind of determine this empirically. 1006 00:37:44,330 --> 00:37:49,550 We can't necessarily use our own intuitions to figure this out. 1007 00:37:49,550 --> 00:37:52,190 Another question is how are costs read, right? 1008 00:37:52,190 --> 00:37:54,000 So in the first study I showed you 1009 00:37:54,000 --> 00:37:56,270 that infants' experience potentially is important, 1010 00:37:56,270 --> 00:37:58,869 or factors that gait infants' experience, right? 1011 00:37:58,869 --> 00:38:00,410 But that's in a situation where there 1012 00:38:00,410 --> 00:38:03,220 aren't a lot of observable cues to effort. 1013 00:38:03,220 --> 00:38:04,970 So I think it may be the case that there's 1014 00:38:04,970 --> 00:38:06,350 some variability here. 1015 00:38:06,350 --> 00:38:09,080 Some costs infants may require experience 1016 00:38:09,080 --> 00:38:12,530 with in order to figure out what is the cost, right? 1017 00:38:12,530 --> 00:38:13,709 How much of a cost is this? 1018 00:38:13,709 --> 00:38:16,250 And maybe there are other costs that infants can more readily 1019 00:38:16,250 --> 00:38:19,250 read from the get go. 1020 00:38:19,250 --> 00:38:21,390 And then, finally, I think at some point, 1021 00:38:21,390 --> 00:38:23,390 we need to ask whether infants and, potentially, 1022 00:38:23,390 --> 00:38:26,622 children are sensitive to other types of costs beyond effort. 1023 00:38:26,622 --> 00:38:29,080 Also, if they have a kind of higher level category of cost. 1024 00:38:29,080 --> 00:38:31,490 So one thing that's really interesting in the literature 1025 00:38:31,490 --> 00:38:33,500 on nonhuman animals is that there are just 1026 00:38:33,500 --> 00:38:36,260 so simple neural systems that are responsible 1027 00:38:36,260 --> 00:38:38,210 for effort reward decision-making, 1028 00:38:38,210 --> 00:38:40,130 and for delay reward decision-making. 1029 00:38:40,130 --> 00:38:42,350 But, obviously, we, as adults, can group these things 1030 00:38:42,350 --> 00:38:44,660 together, or I wouldn't be able to give this talk today, 1031 00:38:44,660 --> 00:38:47,030 and Laura wouldn't have been able to give her talk today. 1032 00:38:47,030 --> 00:38:49,160 So one of the things we have to start to understand 1033 00:38:49,160 --> 00:38:51,530 is when did those things kind of come together 1034 00:38:51,530 --> 00:38:53,940 in service of this larger category of cost. 1035 00:38:53,940 --> 00:38:54,440 OK. 1036 00:38:54,440 --> 00:38:59,200 So I'm going to stop there and ask for questions.