Young Children Want to See Others Get the Help They Need

Robert HepachLeipzig University, Max Planck Institute for Evolutionary

Anthropology

Amrisha Vaish, and Tobias GrossmannUniversity of Virginia

Michael TomaselloDuke University, Max Planck Institute for Evolutionary Anthropology

Children’s instrumental helping has sometimes been interpreted as a desire to complete action sequences or torestore the physical order of things. Two-year-old children (n = 51) selectively retrieved for an adult the objecthe needed rather than one he did not (but which equally served to restore the previous order of things), andthose with greater internal arousal (i.e., pupil dilation) were faster to help. In a second experiment (n = 64),children’s arousal increased when they witnessed an adult respond inappropriately to another adult’s need.This was not the case in a nonsocial control condition. These findings suggest that children’s helping is notaimed at restoring the order of things but rather at seeing another person’s need fulfilled.

When young children see another person in need,they often respond with prosocial behavior such ascomforting (Eisenberg & Miller, 1987; Zahn-Waxler,Radke-Yarrow, Wagner, & Chapman, 1992), inform-ing (Liszkowski, Carpenter, & Tomasello, 2008),sharing resources (Brownell, Svetlova, & Nichols,2009; Svetlova, Nichols, & Brownell, 2010), and moregenerally aiding others in completing their goal-directed instrumental actions (Warneken & Toma-sello, 2006, 2007). Given that these behaviors benefitothers, it is tempting to conclude that children aremotivated by the prosocial desire to enhance others’welfare. However, in order to conclude that earlyprosocial behavior is the result of truly prosocialmotives, alternative explanations first need to beruled out (Hepach, Vaish, & Tomasello, 2013a).

In a recent study, Hepach, Vaish, and Tomasello(2012) addressed one such alternative explanationof instrumental helping behavior, namely, that

children may be motivated to seek out recognitionfor their actions rather than caring for others’ well-being. The authors found that 2-year-old children’sinternal arousal decreased not only when theythemselves returned an object that an adult hadaccidentally dropped but also when they could notprovide help but someone else did so, whereas itremained high when the adult was not helped atall. Furthermore, the greater children’s internalarousal after witnessing the situations, the quickerthey were to help the adult (Hepach et al., 2013a).This suggests that children were not merely moti-vated to “get credit” for helping but were genuinelyconcerned to see the person in need be helped.

Nonetheless, in all documented cases of children’sinstrumental helping, one could hypothesize that thechild is motivated by the social exchange (e.g., Lennon& Eisenberg, 1987) or simply attempting to completea sequence and restore the previous order of thingsregardless of the person’s actual need, for instance,that objects that have been dropped have to be pickedup and put back where they were. This latter alterna-tive interpretation also holds true when consideringthe control conditions of previous studies in whichchildren do not return an object if the adult explicitlydiscards it by intentionally throwing it on the floor,that is, when there is no incomplete sequence (Dun-field, O’Connell, Kuhlmeier, & Kelley, 2011;

We thank all the parents and children who participated in ourstudies and Jana Jurkat and Elvira Portner for their help withrunning the study. The house apparatus was built by HenrikR€othel and decorated by Isabelle de Gaillande-Mustoe, AlinaSch€onfuß, Cleo Meinicke, and Parissa Chokrai. We are gratefulto Jessica B€urgel and Julia Ulber for their help with coding andreliability as well as to Roger Mundry for his advice on statistics.In addition, we thank Robert Schettler for his IT support, RonnyBarr for his support with Adobe, and Karla Schm€olling for herhelp with the videos. This research was partially supported by agrant from the DFG (German Research Foundation) ExcellenceCluster 302: Languages of Emotions.

Correspondence concerning this article should be addressed toRobert Hepach, Department of Research Methods in Early ChildDevelopment, Faculty of Education, Leipzig University, 04109Leipzig. Electronic mail may be sent to robert.hepach@uni-leipzig.de.

© 2016 The AuthorsChild Development © 2016 Society for Research in Child Development, Inc.All rights reserved. 0009-3920/2016/8706-0005DOI: 10.1111/cdev.12633

Child Development, November/December 2016, Volume 87, Number 6, Pages 1703–1714

Warneken & Tomasello, 2006). Indeed, children’sgoal-directed helping (as it also occurs in other nonhu-man primates such as chimpanzees) could be drivennot by a concern for the individual in need but ratherout of a desire to fulfill incomplete action sequences(K€ohler, 1925). Given the parallels between youngchildren’s and nonhuman primates’ instrumentalhelping behavior, the alternative explanations forchimpanzee helping may equally well apply to that ofyoung children (Warneken, Hare, Melis, Hanus, &Tomasello, 2007). Thus, what is commonly referred toas helping may actually be driven by an underlyingnonsocial motive to see the order of things restored.

We conducted two experiments to address thisalternative explanation of young children’s instru-mental helping behavior. We did so by using anexperimental paradigm recently developed byHepach et al. (2012) to study the motives underlyingchildren’s behavior. The authors measured changesin children’s internal arousal via their pupil dilation,an established measure in psychophysiology (Beatty& Lucero-Wagoner, 2000; Laeng, Sirois, & Gre-deb€ack, 2012) indicative of changes in arousal of theautonomous nervous system (Loewenfeld, 1958). Inthe present work, in the first experiment, we investi-gated whether children would help an adult byhanding him the object he needed rather than one hedid not (but which equally served to restore the pre-vious order of things) and whether children’s inter-nal arousal, that is, pupil dilation, was related totheir willingness to help. In the second experiment,we investigated whether children’s internal arousalvaried as a function of whether an actor’s need wasfulfilled by the response of another person (socialcondition) and included a nonsocial control condi-tion in which the movement of objects was identicalto the social condition but no persons were presentand thus there was no unfulfilled need. The twoexperiments were conducted during the same labo-ratory visit in a fixed order for all children. For prac-tical purposes, Experiment 1 was run afterExperiment 2, but we present Experiment 1 first forconceptual reasons and to increase the clarity andcoherence of the article for the reader. Experiment 1serves the function of validating pupil dilation as ameasure of motivation and is therefore foundationalto and facilitates the interpretation of Experiment 2(see Supporting Information for further details).

Experiment 1

The aim of Experiment 1 was to validate the use ofpupil dilation as a measure of internal arousal to

assess children’s motivation to help (see alsoHepach et al., 2012, 2013a) and to investigatewhether children would be sensitive to another’sneed if they could provide help themselves. Chil-dren were presented with a live situation in whichan adult dropped multiple objects that he could notreach, and thus he could not finish his task. Halfthe objects were relevant, the other half irrelevantto his task. Children’s pupil dilation before they gotto help the adult as well as their latency to pick upthe first object were measured. In addition, wecoded for the type of object (relevant or irrelevant)that children picked up first. We hypothesized thatchildren would be more likely to pick up the rele-vant over the irrelevant objects and that the level ofchildren’s arousal would be correlated with theirlatency to help (see also Hepach et al., 2013a).Additional data and analyses are provided in theSupporting Information.

Method

Participants

Participants were 2-year-old children recruitedfrom the department’s database (medianage = 2 years, 1 month, 2 days; age range = 2;0;0–2;2;0). Data collection took place at the Max PlanckInstitute for Evolutionary Anthropology in the mid-sized city of Leipzig, Germany, between May 2012and April 2013. Children came from mixed socioe-conomic backgrounds and all children were nativeGerman speakers. A total of 51 children (25 boys)were included in the final analyses. Six additionalchildren were tested but excluded from the finalsample because of fussiness.

Materials and Design

Children were presented with a wooden houseapparatus (1.35 m wide 9 1.64 m high 9 0.20 mdeep). A window (64 9 68 cm; 46 cm above theground) held the computer monitor (24-in.;52 9 32 cm) at a resolution of 1920 9 1080 pixels aswell as the eye tracking unit (Tobii model X120;Tobii Technology, Stockholm, Sweden) with a sam-pling frequency of 60 Hz and bright pupil capturesetting (see also Jackson & Sirois, 2009) that was usedto measure children’s eye movements and pupildiameter (see Figure 1). Participants’ eyes were cali-brated using a 5-point calibration procedure (see alsoGredeb€ack, Johnson, & von Hofsten, 2010). Stimuluspresentation and data recording was carried outusing Tobii Studio (Version 3.1.3; Tobii Technology).

1704 Hepach, Vaish, Grossmann, and Tomasello

Each child saw two test situations adapted fromWarneken and Tomasello (2006). In one situation,Experimenter 1 (E1) sat behind a table and hung uppieces of cloth with clothes pegs. In another situa-tion, E1 drew a picture with a set of crayons.Placed at the center of the table were 12 objects, 6clothes pegs and 6 crayons. At a predeterminedpoint, E1 “accidentally” dropped all 12 objects onthe floor. A separate preference test with nine par-ticipants (from a different group of children) estab-lished that children at this age do not prefercrayons over clothes pegs. To measure pupil dila-tion, we presented neutral clips (see SupportingInformation and Figure 1) at the beginning of eachtrial (baseline measure) and before children got thechance to pick up objects for the adult (processmeasure). The order of the two test situations andthe color of the neutral clips (blue or purple) werecounterbalanced across children.

To obtain a wider range of values for children’slatency to help the adult we used a distracter toy (ababy swimming pool filled with balls) such that

children had to decide whether to first help theadult or to engage in a fun activity themselves (seealso Warneken & Tomasello, 2012).

Procedure

The experiment was run by three experimentersand was divided into three phases: warm-up, famil-iarization, and test. During the warm-up phase E1played with the child while Experimenter 2 (E2)explained the study to the parent. Parents gaveinformed consent before the study began and wereinstructed to close their eyes while sitting in frontof the monitor during the test phase and to not pro-vide their children with any cues. E2 introducedthe child to the house apparatus. This was thebeginning of the familiarization phase (adaptedfrom Hepach et al., 2012; see Supporting Informa-tion for details). Children followed an exchange ofobjects while sitting in front of the computer moni-tor thus establishing a contingency between E1’sand the child’s side. Furthermore, children wereencouraged to move to the inside and back to theoutside of the house. After the familiarization, E3entered the room and brought with her the dis-tracter toy and placed it at approximately 2.25 maway from E1. E2 and the child examined the dis-tracter toy.

The test phase began with E1 either hanging uppieces of cloth or drawing a picture. After 40 s E2,the parent, and the child moved back in front ofthe house and the child sat on the parent’s lap (seeFigure 1 for a sequence of the test stimuli). Afterchildren saw E1 needing help and after the processmeasure of pupil dilation was taken, parents car-ried their child to the inside of the house to a dis-tance of approximately 2.5 m from E1 andapproximately 2 m from the distracter toy. Childrenwere allowed to move around freely. E1 showed aneutral facial expression and then systematicallyincreased the cues expressing his need for help: (a)alternating gaze between the objects and the child,(b) after 7 s (from the start) reaching for the objectand looking at the child, (c) after 15 s saying “Ohlook child’s name [. . .] Look down there. [. . .] I can-not get to it,” (d) after 30 s directly addressing thechild to ask for help (see Svetlova et al., 2010 for asimilar cue procedure). E1 continued to provide theabove cues until children had picked up at least sixobjects (whether relevant or irrelevant), after whichhe began sorting the objects on the table. If a childoffered him the toy, the adult took it regardless ofwhether or not it was a relevant or an irrelevantone. E1 did not provide the child with any verbal

Figure 1. Apparatus used in Experiment 1 (A and B) and stimu-lus sequence during the test trial (C). Between the two neutralclips, E1 continued his action and after 2 s “accidentally”dropped 12 objects from the center of the table. He expressedconfusion, pretending to not know where the objects went (5 s).

Young Children’s Sensitivity to Others’ Needs 1705

feedback such as “Thank you.” The trial endedeither after children had picked up all the objects orif they did not pick up any objects, then after 45 shad passed. Once children started picking upobjects, the trial did not end after 45 s but endedwhen they had picked up all the objects or if theydisengaged from the activity and moved away fromthe table.

Data Analysis

Pupil dilation. For pupil dilation analyses, onlydata from the neutral clips were used. As an indica-tor of the extent of pupil dilation, we identified theaverage absolute minimum in pupil dilation foreach time point in each test trial (see also Stein-hauer, Condray, & Kasparek, 2000 for a similaranalysis). The idea is that an increase in internalarousal will lead to an inhibited pupillary lightreflex, therefore leaving the pupils more dilated.More specifically, because the neutral clips con-sisted of two presentations of the colorful images,two pupillary light reflexes (PLR) were elicited, andtherefore two absolute minima were obtained. Theaverage of those two minima within a neutralsequence was used for further analyses Measuringpupil dilation in this way greatly reduces noise toallow for single-trial analyses. The identification ofPLRs was standardized using an algorithm writtenin R (version 2.15.1, R Core Team, 2012; see Sup-porting Information for details). On a given trial, aparticipant provided data for two time points: thebaseline measure and the process measure.

Behavioral data. We coded how many objectschildren picked up and how long it took them topick up the first object from the moment whenparents carried children to the marked spot insidethe house until the first object was either placedon the table or in E1’s hand. Children who didnot help were assigned the maximum latency of120 s, which was approximately the duration of atrial until children picked up all the objects. Fur-thermore, we were also interested in whether chil-dren gave a relevant or an irrelevant object to E1first. For this, we identified the type of object chil-dren handed to E1 first. Furthermore, we lookedat the ratio of relevant objects among the first sixobjects children picked up in order to have a morerobust measure of their preference for the type ofobject. The first coder, not blind to hypotheses,coded all the trials. A second coder, blind tohypotheses, looked at a random sample of 30% ofthe data and reliability was high for the totalnumber of objects, j(Cohen) = .95, for the type of

object, j(Cohen) = .89, and for the ratio of correctobjects, j(Cohen) = .91. In addition, agreement forthe latencies was perfect (Intraclass CorrelationCoefficient (ICC) = 1). To assess children’s initial,unbiased responses, we focused our analyses onthe first test trial. Additional data and analyses areprovided in the Supporting Information.

Results

The majority of children (33 of the 51; ~65%)picked up an object. The average number of objectspicked up by a child was 9 (range = 1–12). Further-more, 23 of the 33 (~70%) children picked up a rele-vant object first, binomial test (two-tailed) p = .035.In addition, the average ratio of relevant objectsamong the first six objects (M = 0.6, SD = .28) wassignificantly above chance (50%), t(32) = 2.1,p = .04. Of the 18 children who did not pick up anobject, two stood close to E1 but did not intervene,seven went to the distracter game, and nine chil-dren stayed with their parent. To investigate therelation between children’s pupil dilation and theirmotivation to help, we calculated correlationsbetween both children’s baseline measure and pro-cess measure of pupil dilation and children’slatency to pick up the first object. In case a partici-pant did not pick up an object at all, the maximumlatency value of 120 s was used (see Data Analysis).Children started picking up the first object after25.58 s (SD = 16.3 s), and those children whoshowed greater pupil dilation in the process mea-sure were faster to pick up the first object for theadult, Spearman’s rho (q; n = 45) = �.31; p = .04.Importantly, there was no association between chil-dren’s baseline level of pupil dilation and theirlatency to pick up the first object, q (n = 47) = �.13;p = .37. In addition, there was no difference in chil-dren’s process measure of pupil dilation betweenchildren who picked up the irrelevant object first(M = 3.792, SD = .69) and those who picked up therelevant object first (M = 3.788, SD = .55), t(29) = 0.02, p = .98.

Further analyses revealed no effect of the type ofsituation (crayons vs. clothes pegs) or participants’gender on any of the dependent measures and nodifference in children’s process measure of pupildilation or its relation to the latency to helpdepending on what type of object children pickedup first (ps > .33). Moreover, with regard to themain findings, we obtained the same pattern ofresults on the second test trial though the effectsdid not reach statistical significance (see SupportingInformation for details).

1706 Hepach, Vaish, Grossmann, and Tomasello

Discussion

The aim of Experiment 1 was to investigatewhether children would be sensitive to an adult’sneed by preferentially providing him with theobjects relevant to his task. In addition, we wereinterested in whether there was an associationbetween children’s internal arousal, that is, pupildilation, and their motivation to help. The mainfinding was that children were sensitive to theadult’s need both in their initial choice and whenconsidering the ratio of the first half of objectspicked up. Overall, they preferred to pick upobjects relevant to the adult’s task to those thatwere irrelevant. This finding is particularly strikinggiven that children had to identify the six relevantobjects among a total of 12 objects that haddropped. This is conceivably more demanding thanthe instrumental helping tasks used in previousstudies, in which only one object dropped andhence the only decision children had to make waswhether or not to pick it up (Dunfield et al., 2011;Warneken, 2013; Warneken & Tomasello, 2006).Indeed, the rate of helping in the present study islower than the rate in studies in which only oneobject was dropped but is comparable to the overallhelping rate in other studies in which children hadto pick up multiple objects to help an adult (e.g.,Over & Carpenter, 2009) or in which children werealso presented with a distracter toy (Warneken &Tomasello, 2012). In addition, children had no priorexperience with either type of object. Furthermore,children’s pupil dilation was linked to how quickthey were to pick up the first object for the adult.In other words, the more aroused children werebefore upon seeing the adult needing help, the fas-ter they picked up an object for the adult. Chil-dren’s process measure of pupil dilation was notrelated to the type of object they picked up first,thereby suggesting that this change in internalarousal reflects a general motivation to help ratherthan the specific order in which children want topick up the objects to fulfill others’ needs.

One question that arises is why children did notonly pick up the relevant objects. It could beargued that if children wanted to help the adult,then they should only have picked up the relevantobjects and not the irrelevant ones. A possibleexplanation is that children found it difficult toinhibit an action once they had started it. That is,once the behavior of picking up objects was set inmotion, children continued to do so and the initialmotive to pick up a relevant object for the adulttransferred to a general motive to pick up all the

objects on the floor. In fact, children’s initial motivemay simply have been to help the adult pick up allthe objects and thus help him clean up. Neverthe-less, the important finding is that in doing so chil-dren were sensitive to the adult’s need bypreferentially handing him the relevant object first.

In sum, children were sensitive to the adult’sneed by selectively picking up objects relevant tohis task. The question is whether they did so to seean action sequence completed rather than respond-ing to the adult’s need. This question wasaddressed in a second experiment to investigatewhether children’s internal arousal is indeed trig-gered by another person’s unfulfilled need ratherthan merely by the physical aspects of the situation.

Experiment 2

The aim of Experiment 2 was to investigatewhether children’s arousal is triggered by a socialmotive to see others being helped appropriately. Ifchildren are sensitive to others’ needs, we predictedthat (a) children would anticipate the appropriateresolution, (b) children’s pupil dilation wouldincrease to the need situation, and (c) children’spupil dilation would decrease only if the other’sneed was appropriately fulfilled. We furtherincluded a nonsocial control condition to rule outthat such effects were driven by the physical prop-erties of the situation.

Method

Participants

Participants were 2-year-old children recruitedfrom the department’s database (medianage = 2 years, 1 month, 2 days; age range = 2;0;0–2;1;28). Data collection took place at the Max PlanckInstitute for Evolutionary Anthropology in the mid-sized city of Leipzig, Germany, between May 2012and April 2013. Children came from mixed socioe-conomic backgrounds, and all children were nativeGerman speakers. A total of 64 (32 male) childrenparticipated and were included in the final analy-ses. The total number of participants consisted of 51children who also participated in Experiment 1 plus13 children from the same overall population whoprovided data only for Experiment 2 (see Support-ing Information for details). Additional childrenwere tested but excluded from the final samplebecause of technical failure (n = 2), experimenter/parent error (n = 2), or fussiness (n = 2).

Young Children’s Sensitivity to Others’ Needs 1707

Materials and Design

Two types of videos were used in the experi-ment: action clips portrayed either an adult stackingobjects (social condition) or objects being stackedwithout any person present (nonsocial condition).In addition, based on prior work (Hepach et al.,2012), neutral clips showing colorful bubbles on acolored background were presented at specific timepoints to assess changes in participants’ pupil dila-tion (see also Experiment 1).

In the social condition, one adult (actor) satbehind a table at the center of the screen andanother adult (observer) sat on a chair on the right-hand side of the screen. Five objects of similar kind(e.g., cans) were arranged on the right side of thetable, and two objects were positioned in the center:one relevant object (e.g., another can) and one irrel-evant object (e.g., a shoe). Subsequently, the actorstarted moving three objects, one by one, from theright to the left side of the table while the observerwatched. Next, the actor moved two more objectsfrom the right side to the left side and stacked themon top of the previous three. The observer turnedaway from the scene pretending to read. Whenadult 1 put the fifth can on top of the other four,the two objects in the center of the table “acciden-tally” dropped to the floor and rolled to the centerfront of the scene. The animations of the objectsdropping to the floor were edited into the moviesusing Adobe Premiere Pro to keep the movementsidentical in the social and nonsocial conditions (CS5, version 5.0.3). Adult 1 expressed confusion and,upon seeing the two objects lying on the floor,reached ambiguously between the two objects whiledisplaying an overall neutral expression. After look-ing at the scene for approximately 5 s the observergot up, picked up either the object matching theother five (relevant condition; e.g., the can wasreturned in the can-stacking situation) or the non-matching object (irrelevant condition; e.g., the shoewas returned in the can-stacking situation), andhanded it to the actor. The actor took the object,looked at it, and moved back to an upright positionbehind the table. In the nonsocial condition, one ofthe objects “flew back” on the table.

The timing of events within a segment, for exam-ple, when the objects dropped, as well as the over-all duration of segments was the same for allversions of the clips. In addition, the use of com-puter animation software allowed for the move-ment of objects to be kept identical between thesocial and nonsocial versions of the clips. Further-more, the position of the relevant and irrelevant

objects on the table, and subsequently the side towhich they fell on the floor, was counterbalanced.In order to measure pupil dilation on the samestimulus at specific time points during the presenta-tion of the action clips, the neutral clips were pre-sented while the actor was stacking (baselinemeasure), after he reached for the objects (processmeasure) and after the observer gave one object tothe actor (post measure). The total duration for atest trial was approximately 1 min 40 s.

Each participant watched a different situation oneach test trial (order counterbalanced), one in whichcans were stacked and a shoe was the irrelevantobject and another version in which shoes werestacked and a can was the irrelevant object. Chil-dren were either tested in the social or the nonso-cial condition (between subjects factor). All childrenwere presented with two test trials, one in whichthe relevant object (relevant condition; e.g., a canwas returned in the can-stacking situation) andanother in which the irrelevant object (irrelevantcondition; e.g., a can was returned in the shoe-stacking situation) returned (within subjects factor,order counterbalanced).

Procedure

The experiment was run by two female experi-menters (same experimenters as in Experiment 1)and included a warm-up, calibration, and testphase. During the warm-up, E1 explained the studyto parents, while E2 played with the child. Parentsgave informed consent before the commencementof the experiment and were asked to keep theireyes closed during the study and to not providetheir child with any cues. E2 left the study roomand E1 directed the child’s attention to a computerscreen. Children were seated on their parents’ lap.After the calibration phase, E1 moved behind theparent, out of the child’s view, and the test phasebegan. E2 ran the stimulus presentation procedurefrom a separate room (further details are providedin the Supporting Information).

Data Analysis

Looking time. For each participant, the raw gazedata were corrected based on a procedure devel-oped by Frank, Vul, and Saxe (2012). Each record-ing file was exported from Tobii Studio to Matlab(version 7.12, R2012a) and a series of Matlab routi-nes written by Frank et al. (2012) were adapted forthe present purposes to post hoc correct partici-pants’ point of gaze (see Supporting Information

1708 Hepach, Vaish, Grossmann, and Tomasello

for more details.). For two participants in the socialcondition, no such calibration correction could beperformed because of poor attention and dataacquisition during the video clip, and those subjectswere excluded from further looking time analyses.For the remaining subjects, only samples belongingto a fixation were used. Within Tobii Studio, fixa-tions were defined with a window length of 20 msand a velocity threshold of 30°/s. Furthermore,adjacent fixations were merged with a maximumtime of 75 ms and a maximum angle of 0.5°between fixations. In addition, the crucial time win-dow for analyzing looking behavior were the 13 safter the adult initiated reaching for the two objectson the floor (or the equivalent 13 s in the nonsocialcondition) until the end of that video sequence. Foreach participant, we determined how much timewas spent looking at both object regions of interest(width and height = 195 px; see Figure 2). For sta-tistical analyses, we calculated the proportion oftime children looked at the correct object, that is,time correct object/(time correct object + time incor-rect object). As a control variable, we included thetime (in collected samples) children watchedthe stacking action until the adult reached for theobjects (or the equivalent time point in the nonso-cial control condition). On the first test trial sevenparticipants did not look at the objects in the speci-fied time window (six in the social and one in thenonsocial condition).

Pupil dilation. The procedure for analyzing thedata followed that of Experiment 1. On a giventrial, a participant provided data for the neutralclips at three time points: the baseline measure, theprocess measure, and the postmeasure. Within eachtrial, data from the process and postmeasure werebaseline corrected, for example, in the case of theprocess measure, the difference of the average ofthe two PLRs of the process measure and baselinemeasure was divided by the average baseline mea-sure. Therefore, the actual data points used for fur-ther analyses were the baseline-corrected values forprocess measure and postmeasure. In summary,each participant could provide both process mea-sure and postmeasure for each of the two test trials,that is, four data points in total.

Similar to Experiment 1, we focused our analyseson the first test trial (see Supporting Informationfor additional data analyses). Consistent with ourhypotheses, we carried our three separate statisticalanalyses focusing on (a) children’s looking behaviorafter the objects had dropped, (b) the increase inpupil dilation following the accident, and (c) thechange in pupil dilation depending on how the

situation was resolved (i.e., with the relevant orirrelevant object). For analyses (a) and (b), we rananalyses of variance and the independent factorswere condition (social vs. nonsocial) and gender.For (c), we ran analyses of covariance including thetype of object returned as an independent factor aswell as children’s process measure of pupil dilationas a covariate and gender. Details regarding thechecks of statistical model assumptions are pro-vided in the Supporting Information.

Results

Looking Time

The proportion of time children spent looking atthe relevant object after the objects dropped andbefore the resolution of the situation varied signifi-cantly between the social and nonsocial condition, F(1, 53) = 11.68, p = .001. Children looked signifi-cantly longer at the relevant compared to the irrele-vant object in the social (n = 26; M = 0.76, SD = .27)but not in the nonsocial condition (n = 31; M = 0.53,

Figure 2. Still frame from the moment when the adult was reach-ing for the objects. The regions of interest for both objects aremarked with rectangular shapes. The gaze behavior of partici-pants on the first trial with the relevant object being on the right-hand side is plotted on top of the images to illustrate the focalpoints of attention. Greater visual focus is represented throughred coloring (darker coloring in print). The top panel shows thesummary for the social condition and the bottom panel showsthe summary for the nonsocial condition.

Young Children’s Sensitivity to Others’ Needs 1709

SD = .24), Mann–Whitney U = 622.5, p = .0003. Fur-thermore, children’s longer looking at the relevantobject was significantly above chance, that is, morethan 50% of the time, in the social, Wilcoxon exactT = 315, n (without ties) = 26, p = .0001, but not inthe nonsocial condition, T = 288, n = 31, p = .44 (seeFigures 2 and 3A). There was no statistical effect ofgender (p = .99) or the time children spent lookingat the stacking action (p = .83). Overall, childrenshowed anticipatory looking toward the relevantobject in the social but not in the nonsocial controlcondition. The same pattern of results and a statisti-cally significant effect of condition emerged whenconsidering both test trials (see Supporting Informa-tion for details).

Pupil Dilation

The initial change in children’s pupil dilation dif-fered between the social and the nonsocial conditions,F(1, 61) = 4.01, p = .0497 (see Figure 3B). Children’spupil dilation increased more from baseline to processwhen watching the objects drop in the social (Mso-

cial = 0.07, SDsocial = .07) compared to the nonsocial con-dition (Mnonsocial = 0.04, SDnonsocial = .04), T = 363,n = 32, p = .046. In addition, girls (Mgirls = 0.07,SDgirls = .06) showed more increase in pupil dilationthan boys (Mboys = 0.04, SDboys = .05),b = �.03 � .01, t(59) = �2.39, p = .02. Moreover, thesame pattern of results was obtained when consider-ing both test trials, though no statistically significant

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CPost change in Pupil Dilation

Increase in Pupil Dilation (Process Measure)

Figure 3. Data illustration of children’s anticipatory looking and changes in pupil dilation on the first test trial. (A) For each participantthe proportion of time looked at the correct object (divided by the time looked at both objects) after the objects dropped is plotted forboth conditions. The gray circles represent the means. **p < .01. (B) The increase in children’s pupil dilation before the resolution of thesituation is plotted for both conditions. The means are illustrated by gray circles. The standard deviation is indicated by the black lines.*p < .05. (C) Children’s change in pupil dilation after the resolution of the situation depending on the initial increase in arousal. The leftpanel shows the data for the nonsocial condition. The solid lines represent the model lines. The right panel shows the data for the socialcondition with the model lines. Only in the social condition, when the irrelevant object was returned, did children show a pattern dif-ferent from values regressing to the mean, that is, only in this condition did large and small values in the premeasure align with largeand small values in the postchange measure, respectively.

1710 Hepach, Vaish, Grossmann, and Tomasello

effect of condition emerged (see Supporting Informa-tion for details).

To investigate changes in children’s pupil dila-tion in response to the resolution of the situationwe ran two separate analyses, one for the socialand the other for the nonsocial condition. Therewas a significant interaction between children’s ini-tial increase in pupil dilation and object relevancyin the social, F(1, 27) = 9.62, p = .004, but not in thenonsocial condition, F(1, 27) = 0.001, p = .98. Thatis, the more children’s internal arousal increased byseeing a person needing help, the more theyremained aroused only if the irrelevant object wasreturned (b = .01) and the more it decreased againif the relevant object was returned (b = �.05). Therewas no statistical effect of gender (p = .24). In thenonsocial condition, the initial arousal decreasedagain regardless of whether the irrelevant(b = �.01) or the relevant (b = �.009) object wasreturned (see Figure 3C). There was no statisticaleffect of gender (p = .44). Overall, the same patternof results reached statistical significance whenincorporating both test trials. For all dependentmeasures, additional analyses revealed no effect oftype of situation (stacking cans vs. stacking shoes)or of the location of the relevant object (left or right;see Supporting Information for details).

Discussion

The aim of Experiment 2 was to investigatewhether children’s internal arousal is triggered by asocial motive to see others being helped appropri-ately. In accordance with our predictions, we foundthat (a) children anticipate the appropriate solutionof another’s situation, (b) children’s pupil dilationincreases to the need situation, and (c) children’spupil dilation decreases only if the other’s needwas appropriately fulfilled (or when it did not mat-ter, as in the nonsocial control). In other words,children’s internal arousal remained high if an adultneeding help was given an object that did not ade-quately fulfill his need even though the physicalorder of things was restored in part and the adultstopped reaching. We included a nonsocial controlcondition and found that the effects on anticipatorylooking and pupil dilation were not driven purelyby the physical properties of the situation.Together, these results suggest that children’s inter-nal arousal increases as a consequence of witness-ing a person needing help, and it remains high ifappropriate help is not provided. Children are sen-sitive to others’ needs and expect others to behelped appropriately.

The fact that children’s pupil dilation increasedmore in the social compared to the nonsocial condi-tion does not mean that children did not respondto seeing objects drop in the nonsocial condition,because in that case children’s pupil dilation alsoincreased (see Figure 3B), possibly as a function ofthe complexity of the situation (see also Jackson &Sirois, 2009). Our results in the social condition areconsistent with previous work on infants’ under-standing of social interaction showing that infantsshow more pupil dilation as a consequence of see-ing incongruent displays of emotional faces andactions (Hepach & Westermann, 2013) and unusualsocial interactions (Gredeb€ack & Melinder, 2010). Inthe present study, seeing an adult not providingthe appropriate help could be seen as an unusualinteraction or a resolution that is incongruent withwhat the adult needs. The additional effect thatgirls showed greater increase in pupil dilation thanboys after witnessing the problem could suggestthat girls became more involved than boys (see alsoFabes, Eisenberg, & Eisenbud, 1993). However, wefound no gender effect on children’s pupil dilationafter they saw the situation being resolved, suggest-ing that boys and girls alike were sensitive to see-ing the adult’s need fulfilled appropriately.

General Discussion

The main finding of the present experiments is thatchildren want to see others get the help they need.In a situation where 2-year-old children themselvesget the chance to help an adult and have to dis-criminate relevant from irrelevant objects, theyselectively hand the adult the objects he needs(Experiment 1). Although the task was conceivablydemanding, given that multiple objects dropped,children nevertheless preferably chose to help byhanding over the relevant objects first. During thosesituations children’s own level of internal arousalrelated to how quick they were to pick up the firstobject for an adult who could not reach it himself(as also reported by Hepach et al., 2013a). Further-more, when children are observers of a situation inwhich an adult needs help, they expect to see therelevant solution and their own internal arousalincreases and remains high if the adult does not getthe relevant object he needs to finish a task (Experi-ment 2).

These findings contribute to the results from pre-vious studies on children’s prosocial behavior asthey clarify the nature of young children’s motiva-tion to fulfill others’ instrumental goals. Although

Young Children’s Sensitivity to Others’ Needs 1711

prior work has shown that young children can bemade aware of other’s needs (e.g., Brownell et al.,2009; Svetlova et al., 2010; Warneken, 2013), thepresent experiments show that children at the ageof 2 spontaneously prefer to help in ways that areappropriate to another person’s unfulfilled need.The motivation is not only intrinsic (Warneken &Tomasello, 2008) but appears to be specifically trig-gered by the social component of the situationgiven that the nonsocial condition in the presentstudy failed to elicit a similar degree of involve-ment and attention.

Furthermore, the correlation we found in Experi-ment 1 replicates a previous finding that 2-year-oldchildren’s arousal state upon seeing a person needhelp correlates with their latency to help that per-son (see Hepach et al., 2013a). Importantly, ourmeasure of children’s baseline level of pupil dila-tion did not correlate with their latency to help,showing that the main source for the correlationwas not simply children’s baseline state of arousalbut specifically their arousal in response to seeingthe person need help. This further validates the useof physiological measures such as pupil dilation toassess children’s motivation to help (see also Fabeset al., 1993; Hastings, Zahn-Waxler, & McShane,2006). It is important to note that the results fromExperiment 1 suggest that the degree to which chil-dren’s internal arousal changes to others’ in needreflects a more general motivation to help ratherthan reflecting the specific in which children wantto help those in need.

Whereas previous studies had investigated whenand how often young children help others (e.g.,Dunfield et al., 2011; Svetlova et al., 2010; Warne-ken & Tomasello, 2006, 2007, 2013), the presentwork further specifies the motivational mechanismunderlying early helping behavior. First, pupil dila-tion is not a measure of a specific emotion such assympathy or a particular thought but rather asymptom of psychological engagement. At anygiven time, such a state of increased engagement isinfluenced by both affective and cognitive factors.Therefore, pupil dilation reflects the degree ratherthan the nature of a psychological process. Impor-tantly, in the case of motivation the degree of chil-dren’s change in pupil dilation is indicative of howmuch they were engaged by the process ofincreased tension toward the adult’s unfulfilled goal(see also Hepach et al., 2013a). In previous work,changes in pupil dilation have been used to mea-sure infants’ and young children’s responses tonovel events in violation of expectations paradigms(e.g., Gredeb€ack & Melinder, 2010; Jackson & Sirois,

2009). The fact that, in the current Experiment 2,children’s pupil dilation increased if the adult wasnot helped appropriately may be conceived of as aresponse to an unexpected event. Children remainpsychologically engaged if others’ needs are not ful-filled appropriately. In addition, the increase inpupil dilation in Experiment 2 suggests that chil-dren become engaged as they witness others in needof help. Furthermore, while the results from Experi-ment 1 show that changes in pupil dilation arelinked to motivational strength, the results ofExperiment 2 show (a) that this increase is greaterwhen the misplaced objects matter for another per-son and (b) that this triggered engagement is main-tained if the adult is not helped appropriately.Therefore, the present paradigm offers an approachto studying the underlying motives of behaviormore generally.

It is important to note that the present experi-ments only assessed the case of children’s instru-mental helping for the age group of 2 years.Children’s helping occurs in a variety of domainsand can be specified according to the type of assis-tance children provide for others, for example,goods, information, and service (Warneken &Tomasello, 2009). Likewise, children’s helping canalso be categorized according to the type of need towhich they are responding (e.g., material, emo-tional, and instrumental; Dunfield et al., 2011). Theresults from the present experiments address themotivation of children to provide instrumental help.For the emotional helping domain, other studieshave shown that children’s empathic responding isindicative of their readiness to help another person(Eisenberg & Miller, 1987; Zahn-Waxler et al., 1992)and that this empathic responding relies to a greatextent on children’s appreciation of the context inwhich it occurs (Hepach, Vaish, & Tomasello,2013b; Vaish, Carpenter, & Tomasello, 2009). Theadult in the present experiments retained a neutralemotional expression suggesting that the effects onchildren’s anticipatory looking and pupil dilationwere not driven purely by an actor’s sad emotionalexpression. This is consistent with previous workdemonstrating that children help an adult to anequal degree regardless of whether she displays asad or a neutral emotional expression (Newton,Goodman, & Thompson, 2014). Nevertheless, thepresent findings—and in particular the internalarousal evident when children see others in need—may describe the more general mechanism of chil-dren’s motivation to help, which could also applyto other domains of prosocial behavior not limitedto instrumental helping. Further research is needed

1712 Hepach, Vaish, Grossmann, and Tomasello

to identify whether children show similar changesin internal arousal in situations in which othersneed comfort, information, or resources.

One additional interesting avenue for futureresearch is the systematic investigation of the devel-opment of children’s motivation to help others.Children’s prosocial behavior emerges as early as12 months for the case of informative pointing(Liszkowski et al., 2008) and at 14 months childrenbegin to help others achieve their instrumentalgoals (Warneken & Tomasello, 2007). It is possiblethat for those younger age groups systematicchanges in pupil dilation reveal their motivation tohelp others, too. On the other hand, children’s help-ing at earlier ages could be motivated by the socialengagement of the situation. Another related ques-tion is how the results of the present study relate toother domains of social and motor development,for example, whether children would respond withincreased pupil dilation to others not being helpedappropriately before they themselves have themotor abilities to help others. In this sense, the pre-sent experiments provide a starting point for futureresearch on the development of children’s intrinsicmotivation to help others. As children grow older,their motivation to help others may change andnew motives to help, for example, increased con-cerns for reciprocity, begin to emerge.

In summary, the present results critically extendprior work on the ontogeny of helping behaviorby demonstrating that in cases where childrenhelp an adult overcome a physical obstacle, theyare not simply motivated to see the order ofthings restored. Rather, children’s own internalarousal is mediated by how well another person’sneed is fulfilled. Importantly, by using a closelymatched nonsocial condition we were able to ruleout the crucial alternative explanation that childrenwere merely responding to perceptual aspects ofthe situation, that is, that they simply wanted tosee dropped objects returned to their place or seesimilar objects placed together. Therefore, itappears unlikely that early helping behavior is dri-ven by a concern to “get credit” (Hepach et al.,2012) or driven solely by a desire to completesequences—both of which have been given as pos-sible explanations nonhuman primate helpingbehavior (e.g., K€ohler, 1925). Instead, the presentresults lend support to the hypothesis that youngchildren’s helping behavior is guided by anotherperson’s unfulfilled need. Thus, children genuinelycare to see others’ well-being maintained orincreased.

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Supporting Information

Additional supporting information may be found inthe online version of this article at the publisher’swebsite:

Figure S1. An Example Sequence for the Nonso-cial Condition Showing the Situation of StackingCans

Table S1. Children’s Process Pupil DilationDepending on Their Behavior if They Did Not Helpthe Adult

Table S2. Results of the Analyses for the ModelInvestigating Children’s Looking at the ObjectsPrior to the Resolution of the Situation

Table S3. Results of the Analyses for the ModelInvestigating Children’s Looking at the ObjectsPrior to the Resolution of the Situation Incorporat-ing Both Test Trials

Table S4. Results of the Analyses for the ModelInvestigating Children’s Looking at the SituationIncorporating Both Test Trials

Table S5. Diagnostics for the Model on Chil-dren’s Change in Pupil Dilation After Witnessingthe Objects Drop

Table S6. Results of the Analyses for the ModelInvestigating Children’s Process Measure of PupilDilation Prior to the Resolution of the Situation

Table S7. Results of the Analyses for the ModelInvestigating Children’s Process Measure of PupilDilation Prior to the Resolution of the SituationIncorporating Both Test Trials

Table S8. Results of the Analyses for the ModelInvestigating Children’s Postmeasure of Pupil Dila-tion After the Resolution of the Situation

Table S9. Summary of Predictors for the FullModel Including Both Test Trials With the Post-change in Children’s Pupil Dilation (After the Reso-lution of the Situation) as the Dependent Measure

Appendix S1. Additional Experiments

1714 Hepach, Vaish, Grossmann, and Tomasello