Inferring the goals of a nonhuman agent

Susan C. Johnsona,*, Amy Boothb, Kirsten O’Hearnc

aDepartment of Psychology, Jordan Hall, Building 420, Stanford University, Stanford, CA 94305, USAbNorthwestern University, Evanston, IL, USAcUniversity of Pittsburgh, Pittsburgh, PA, USA

Received 1 January 2000; accepted 1 January 2001

Abstract

Johnson, Slaughter, and Carey [Dev. Sci. 1 (1998) 233.] used infants’ ability to follow

the ‘gaze’ of novel objects to claim that infants’ recognition of mentalistic agents is not

isomorphic with person recognition but rather based on a set of nonarbitrary object

recognition cues including the presence of a face and the ability to interact contingently with

other agents. The current studies extend these findings with data based on infant imitation

and the production of communicative gestures. The first study replicated Meltzoff’s [Dev.

Psychol. 31 (1995) 838.] reenactment of goals paradigm with a novel, nonhuman agent.

Fifteen-month-olds were found to reenact both the completed and uncompleted/unseen

goals of a novel object that had a face and interacted contingently with the experimenter and

infant. Concurrently, infants directed many communicative gestures at the object. A second

study excluded the possibility that the communicative gestures apparently directed at the

object in Study 1 were in fact imitations of the experimenter’s own behavior. The

suggestion that novel, nonhuman objects are capable of eliciting such divergent behaviors

as gaze-following, goal reenactment, and communicative gestures from infants, supports

the claim that all of these behaviors are mediated by a central conceptual notion of

mentalistic being, at least by the ages studied, and that that concept is not isomorphic with

the concept person. D 2001 Elsevier Science Inc. All rights reserved.

Keywords: Mentalistic agents; Infant social cognition; Nonhuman agent

0885-2014/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved.

PII: S0885 -2014 (01 )00043 -0

* Corresponding author. Tel.: +1-650-725-8964.

E-mail address: scj@psych.stanford.edu (S.C. Johnson).

Cognitive Development 16 (2001) 637–656

1. Introduction

One commonly held position in the study of infant social cognition is that (1)

infants distinguish between people and nonpeople and (2) infants’ earliest

understanding of other minds maps directly onto this distinction. While the first

claim has been well documented, the second has been largely taken for granted

(see Johnson, 2000; Legerstee, 1992, 1994; Meltzoff, 1995; Poulin-Dubois,

1999; Wellman, 1993 for related reviews). This second point can be broken

down into two related questions. When do children first attribute mental states to

others and when they do, whom do they attribute mental states to? The answer to

these questions may well provide insight into the nature of the representational

systems underlying mentalistic reasoning.

Mental states are unobservable constructs that must be inferred by observers

rather than perceived directly. They are distinguished from other sorts of

unobservables or internal states by the specific kind of relationship they hold

with the world. That is, mental states are directed at the world; they are about

things. Other commonplace, commonsense unobservables (e.g., life, essences,

atoms, etc.), although presumed by lay thinkers to exist in the world, are not

presumed to be about the world. The ability to construe ourselves and others as

agents with mental states such as perceptions, attention, desires, and beliefs is

critical. With this mentalizing ability, we can communicate referentially, predict

and explain others’ behaviors, and manipulate both our own and others’ mental

states for the purposes of complex problem-solving and learning, not to mention

deception. Mentalizing is so critical, in fact, that its absence is thought by some

to be a central cause of autism (Baron-Cohen, 1995; Baron-Cohen, Tager-

Flusberg, & Cohen, 1993).

Garnering evidence sufficient to demonstrate mentalizing is difficult how-

ever. Many behaviors that could potentially serve as indices of mentalizing

(e.g., gaze-following, pointing, and goal imitation) can typically be interpreted

in both mentalistic and nonmentalistic ways. Nonmentalistic explanations

based on signal releasers, attentional enhancement, and object affordances

have all been proposed to explain the variety of behaviors produced by

prelinguistic infants (Butterworth & Jarrett, 1991; Gerwitz & Pelaez-Nogueras,

1992; Hood, Willen, & Driver, 1998; Moore & Corkum, 1994). The inter-

pretative problems are particularly acute for the attribution of mental states that

are correlated with reality (e.g., perception or goals) and can thus be mimicked

by conditioned or reality-driven behaviors. It was this problem that led Dennett

(1978) to suggest that the only convincing evidence for mentalizing must come

from successful reasoning about false beliefs, because false beliefs drive

behaviors not otherwise predicted by reality. Dennett’s argument motivated

an entire generation of research on the development of successful false belief

reasoning in children between the ages of 2 and 4 years (Flavell & Miller,

1998; Fodor, 1992; Gopnik & Astington, 1988; Leslie, 1994a; Wellman, 1993;

Wimmer & Perner, 1983).

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656638

Although the point is well-taken, the absence of successful false belief

reasoning before the age of 4 does not mean that younger children and infants

do not attribute any mental states to agents; only that sufficient evidence for such

a claim is difficult to generate. It does mean, however, that as long as the agents

used to test infants’ competency are highly familiar to infants, as are people,

nonmentalistic explanations are difficult, if not impossible, to rule out. Much of

the work in this area has nonetheless presupposed the role of people in infants’

attributions of mental states. Between the ages of 9 and 18 months, infants have

begun to interact with people as though they believe people have minds. They

produce communicative gestures such as points, requests, and displays for other

people (Bates, Camaioni, & Volterra, 1975; Bretherton, McNew, & Beeghly-

Smith, 1981; Butterworth & Grover, 1988; Leung & Rheingold, 1981); they

follow adults’ gazes (Butterworth & Jarrett, 1991; Corkum & Moore, 1998;

D’Entremont, Hains & Muir, 1997; Lempers, 1979; Scaife & Bruner, 1975) and

they guide their own behavior toward objects on the basis of other people’s

emotional and goal-directed behavior toward those objects (Baldwin & Moses,

1996; Meltzoff, 1995; Repacholi & Gopnik, 1997; Woodward, 1998; see also

Johnson, 2000 for a recent review).

The emphasis on humans as the target of infants’ mentalizing is not accidental.

A great deal of evidence has accumulated showing that very young infants can

and do distinguish between humans and nonhumans. At birth, infants preferen-

tially track the movement of faces (Morton & Johnson, 1991) and imitate the

facial and hand gestures of people (Field, Woodson, & Greenberg, 1982; Meltzoff

& Moore, 1977, 1983) but not inanimate objects (Legerstee, 1991). From 3

months to 1 year, infants smile, vocalize, and gesture more in the presence of

people than inanimate objects while visually fixating and reaching more towards

animals or inanimate objects, even when the inanimate objects resemble people in

very salient ways both perceptually and behaviorally such as dolls, interactive

robots, and animals (Ellsworth, Muir, & Hains, 1993; Klein & Jennings, 1979;

Legerstee, 1994, 1997; Legerstee, Pomerleau, Malcuit, & Feider, 1987; Poulin-

Dubois, Lepage, & Ferland, 1996; Ricard & Allard, 1993; but see Frye, Rawling,

Moore, & Myers, 1983 for contradictory results).

The ability to discriminate people from nonpeople, however, is no more

sufficient evidence of mentalizing abilities than any of that described above. It is

possible that person discrimination could develop in support of important social

and cognitive processes that are independent of mental state attributions (e.g.,

attachment and/or observational learning). Neither is person discrimination

logically necessary for mentalizing abilities. That is, object recognition processes

for identifying mentalistic agents need not be isomorphic with the processes for

identifying people.

Given these two concerns, (1) the problem of interpreting infants’ behavior

in the context of highly familiar agents like people and (2) the still under-

specified function of the person/nonperson distinction in infancy, it may be time

to look more closely at infants’ interpretation of nonhumans. It is particularly

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 639

important to do so using measures that are more directly associated with

mentalizing abilities, such as communicative behaviors, joint attention behav-

iors, and so on.

In fact, several largely untested theoretical proposals have been offered about

the cues that lay thinkers may use to identify mentalistic agents, human or

otherwise. The features proposed fall into several overlapping classes: morpho-

logical features such as faces and eyes (Baron-Cohen, 1995; Carey & Spelke,

1994, 1996), asymmetry along one axis (Baron-Cohen, 1995; Premack, 1990,

1991), nonrigid transformation (Gibson, Owsley, & Johnson, 1978), self-propul-

sion (Baron-Cohen, 1995; Leslie, 1994b, 1995; Premack, 1990, 1991), and the

ability to engage in contingent and reciprocal interactions with other agents

(Spelke, Phillips, & Woodward, 1995; Premack, 1990).

Drawing on these proposals, Johnson, Slaughter, and Carey (1998) examined

whether any of the cues would elicit gaze-following (a putative reflection of

mentalizing) by 12-month-olds in the context of a novel, nonhuman object. To do

this, they created a small novel object that could be introduced to infants as the

agent in a standard gaze-following paradigm (Scaife & Bruner, 1975). Infants’

willingness to follow the ‘gaze’ of the object when it reoriented itself in space

was then measured. Several potential mentalistic cues were studied, including the

presence of a face, self-generated behavior/movement, and contingent interaction

with the subject. Only the presence of a face and/or the ability to interact

contingently with the infant elicited gaze-following by the infant. Importantly,

infants did not follow the gaze of the same faceless object producing exactly the

same self-generated behaviors seen in the contingent condition if those behaviors

were not contingent upon the infants’ own behavior. Based on this, Johnson et al.

argued that around the same age that infants seem able to attribute mental states

such as perception and attention to people (12 months), infants also seem able to

attribute these mental states to novel entities other than people.

Of course, even these findings could be reinterpreted as a generalization of

previously conditioned behavior from people to novel objects that share some

relevant but nonmentalistically interpreted feature (e.g., see Corkum and Moore’s

(1998) account of gaze-following in infancy), thus leading us back to Dennett’s

original quandary. However, nonmentalistic accounts in this domain give rise to a

prediction not made by the theorists described above. That is, under non-

mentalistic accounts, the infant’s behavioral competency will vary across differ-

ent behavioral contexts (e.g., gaze-following, communication, and imitation). For

instance, in an account of gaze-following based purely on conditioned associa-

tions, there is no reason to assume that the production of head turns as seen in

gaze-following should agree with measures of object manipulation as seen in

imitation. Similarly, with signal-releaser accounts, different behavioral responses

will depend on the existence of independent, evolutionarily specified mecha-

nisms. Conversely, the degree to which putative mentalizing is manifested across

a variety of diverse behaviors and contexts is evidence against nonmentalistic

interpretations. It is, therefore, all the more important to reexamine the person/

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656640

nonperson distinction in infancy using as wide a variety of putative mentalizing

behaviors as possible.

The current study is a first attempt to extend this reasoning and the results

of Johnson et al. (1998) to behavioral contexts other than gaze-following. If

results consistent with mentalistic interpretations are obtained in divergent

methodological paradigms, objections based on local interpretative issues of

individual methods will no longer obtain. To this end, two additional behav-

ioral methods have been adapted in such a way that infants can be introduced

to a novel, contingently interacting agent and then given the opportunity to (1)

reenact the agent’s unseen goals (Meltzoff, 1995) and (2) interact communica-

tively with the agent by directing greetings, object requests, and object displays

at the agent.

2. Study 1

In Meltzoff’s (1995) paradigm, 18-month-olds were shown to reenact the

object-related goals of human actors (for instance, dropping a string of beads into

a cup). When a human actor tried but failed to accomplish his goal, 18-month-

olds reenacted the inferred, unseen goal rather than the spatiotemporally

witnessed event. Meltzoff argued that the infants’ performance could not be

motivated purely by the spatiotemporal information in the action itself, because in

a condition in which the human actor was replaced by a mechanical set of pincers

performing the same spatiotemporal actions, infants failed to reenact any unseen

actions. Meltzoff attributed this differential behavior to an early naive psychology

based on and restricted to the infants’ knowledge of people.

Study 1 examines the degree to which infants do in fact restrict their

attribution of goals to human actors. A nonhuman actor is used that, like the

novel object in Johnson et al. (1998) and unlike Meltzoff’s mechanical pincers,

embodies some of the characteristics thought to imply the presence of a mind,

specifically the presence of a face and hands, self-generated behavior, and the

ability to engage in contingent interactions.

2.1. Method

2.1.1. Participants

Fifty-six 15-month-olds (M = 15 months 12 days; range 14 months 27 days–

15 months 28 days) completed three conditions: Baseline (n = 20), Completed

Target Actions (Complete; n = 16), and Incompleted Target Actions (Incomplete;

n = 20). Infants were recruited through a mailing list of new parents in a mid-

Atlantic American city. Only healthy, full-term infants were included. Nine

infants were excluded for fussiness (2), experimenter error (3), equipment error

(1), and for failing to engage in the task by refusing to touch any toys (2; both in

the Complete condition).

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 641

2.1.2. Materials

2.1.2.1. The agent. A store-bought stuffed orangutan was adapted in the lab to

fit these requirements (see Fig. 1). The orangutan was approximately the size of a

15-month-old infant, sitting 18 in. high and 12 in. wide. It was covered in long

reddish-brown fur, with black vinyl hands, feet, and belly. It also had a black

vinyl face with two brown glass eyes and a nose sculpted of the same black

fabric, but no mouth. The face was encircled with long white fur. The

orangutan’s arms and hands were modified to allow an experimenter to fit his

or her own hands and arms inside them in the manner of a puppeteer. When

operated by the puppeteer, the orangutan agent was capable of contingent and

reciprocal action with both the experimenter and infant as well as perceptually

guided and goal-directed behavior and possessed the morphological features of

both a face and hands. It also necessarily exhibited self-generated and bio-

logically real movement. The experimenter operating the orangutan never spoke

or produced any sounds.

2.1.2.2. The setup. The child was seated on a caretaker’s lap at a table. The

orangutan agent was seated on top of the table directly across from the infant.

The orangutan backed up against a floor-length curtain behind which sat the

puppeteer. Two holes were cut in the curtain, allowing the puppeteer to extend

Fig. 1. The novel agent for Study 1 (left) and the surrogate for Study 2 (right).

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656642

her/his own arms through the curtain and into the arms of the orangutan (see

Fig. 2). The puppeteer’s own arms were never visible to the infant. The

puppeteer could watch the scene in front of the curtain via a TV monitor linked

to a videocamera that was mounted to the side of the setup and on which the

entire procedure was videotaped.

2.1.2.3. The objects. Four object sets compatible with the manual dexterity of

15-month-olds were selected, including beads in a cup, an elastic band on a peg, a

dumbbell, and a cap placed on a column (see Fig. 3).

2.1.3. Procedure

The experimental procedure followed Meltzoff’s (1995) original paradigm as

closely as possible. Infants were randomly assigned to one of the three

conditions: the Completed Action condition, the Incompleted Action condition,

or the Baseline condition.

2.1.3.1. The warm-up period. In all three conditions, the experimental trials

were preceded by a brief period designed to allow infants to acclimate to the

presence of the novel orangutan. The experimenter brought the infant into the

experimental room with their caretaker and introduced the infant to the

Fig. 2. The experimental setup for Study 1.

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 643

orangutan. The experimenter called the agent by name (‘‘Tang’’) and encour-

aged the infant to wave and ‘‘say hello to Tang.’’ The agent also waved to the

infant at the experimenter’s request. The infant was then encouraged to play

with a warm-up toy — a wooden box with an accompanying block — in the

presence of the orangutan. A variety of holes were cut in the lid of the box so

that differently shaped blocks could be dropped through. The infant was

allowed to keep the toy briefly, then she was asked to pass it to ‘‘Tang’’ so

that ‘‘Tang could have a turn.’’ The agent reached out his hands to accept the

toy and played with it by dropping the block into one of the holes. The

Fig. 3. The object sets for Study 1.

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656644

experimenter then asked him to give the toy back to the child. This continued

until the experimenter judged the child to be comfortable enough in the

orangutan’s presence to attend to the experimental task and had at least

touched the toy. In all cases, all of the information provided to the infant

about the orangutan and its behavioral capabilities during the warm-up period

was also available during the experimental trials. Following the warm-up

period, each infant completed four experimental object trials, including the

dumbbell, beads in a cup, an elastic band on a peg, and an inverted cup

placed on a column.

2.1.3.2. Completed and Incompleted Action trials. In the Completed and

Incompleted conditions, the child watched the agent act on each set of objects

three times, either successfully or unsuccessfully (see below). The object(s) was

then placed in front of the child by the experimenter in the same orientation used

with the agent. Each test trial lasted 20 s from the moment the child first touched

one of the objects. They were as follows.

The cup and beads. In all cases, the cup was presented to the agent (and the

child) upside down with the beads placed on the table to the side of the cup. For

the completed action, the agent turned the cup over, picked up the beads, lifted

the string above the edge of the cup, and dropped the beads inside the cup. This

was repeated three times with the experimenter retrieving the beads and inverting

the cup between each attempt. For the Incompleted action, the agent turned the

cup over, picked up the beads, lifted the string above the edge of the cup, wavered

slightly over the cup, and then dropped the beads so that they landed just outside

the cup on the table. Again, this was repeated three times, each in a slightly

different fashion by alternating hands and having the beads land in a different

spot on the table each time.

The peg and elastic band. The peg was always presented with the board flat

on the table and the peg sticking straight up. The elastic band was placed on the

table next to it. For the completed action, the agent uprighted the board so that the

peg was parallel to the surface of the table. Then, it picked up the elastic band and

hung it on the peg. In the Incompleted action, the agent uprighted the board,

picked up the elastic band, and raised it up toward the peg while releasing it just

before it circled the peg, thus dropping it on the table. Again, this was attempted

three times, alternating hands each time.

The dumbbell. For the completed action, the agent simply grasped one end

of the dumbbell in each hand and with an exaggerated effort pulled the two

ends apart. In the Incompleted action, the agent grasped the dumbbell the same

way, exerted the same exaggerated effort, but allowed one hand to slip off the

end of the dumbbell before it came apart. The hand that slipped alternated

between attempts.

The column and cap. For this item, the column was always presented on its

side, with the cap presented in an inverted position next to it. For the completed

action, the agent uprighted the column, picked up and turned over the cap, and

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 645

then with an exaggerated motion placed the cap on the column, leaving it resting

on top. In the Incompleted action, the agent went through the same motions but

never fully fit the cap into a level position on the column so that when it was

released it fell to the table. Again, the hands were alternated between attempts.

2.1.3.3. Baseline trials. In the Baseline condition, each trial began with the

child being allowed to manipulate the object(s) for 20 s. After the child

manipulated the object(s), they were given to the agent. The agent then randomly

manipulated them in a non-goal-directed way for 20 s. The agent was given a turn

with the objects in order to keep the overall level of activity, interest, and pace of

the trials comparable to the other conditions.

The order of objects was counterbalanced across all three conditions.

2.2. Results

Infants were said to have produced a target outcome if they satisfied the

following criteria.

2.2.1. The cup and beads

Any action that placed the beads in the cup with or without touching the

bottom was counted as a success. Infants need not actually release the beads,

although if they did and some of them fell over the edge of the cup or if they

knocked the cup over, this was not counted against them.

2.2.2. The peg and elastic band

Any action that placed the elastic band over the peg such that the peg

protruded through the center of the band was counted as a success. The

orientation of the peg and board relative to the table was ignored.

2.2.3. The dumbbell

Any action that resulted in the dumbbell coming apart into two separate parts

was counted as a success.

2.2.4. The column and cap

Any action that succeeded in orienting the inverted cap over the end of the

upright cone so that the cap was more horizontal than vertical was considered a

success regardless of whether the infant released the cap.

Three infants (one in the Completed and two in the Incompleted conditions)

completed only three of the four object trials. One infant in the Baseline condition

completed only two of the four trials. For the purpose of data analysis, missing

data in those cases were replaced by the mean for that subject. Otherwise, a blind

coder coded all of the infants’ behaviors from videotape. A second coder

achieved 93% agreement with the first coder. Disagreements were resolved

through review and discussion of the tapes.

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656646

Preliminary analyses revealed no main effects of sex so it was removed from

further analyses. The resulting overall mean values for each condition and item

are shown in Table 1. An analysis of variance (ANOVA) was performed on the

remaining factors of Condition (between-subjects) and Item (within-subjects).

A main effect of Item was found [F(3,159) = 3.02, P < .001], possibly reflect-

ing the low rate of reproductions with the peg relative to the other items.

(Review of the tapes suggested that the hairband used to loop over the peg was

in fact too difficult for the children to manipulate.) Importantly, there were no

Item�Condition interactions. Therefore, it does not appear that the overall low

production rate of the peg outcome should interfere with our ability to interpret

any effects of Condition, the factor of central interest. The Condition factor

produced a main effect [F(2,159) = 6.56, P < .001].

Infants produced the target outcomes only 10% of the time in the Baseline

condition, thus confirming that these outcomes were rarely produced sponta-

neously by infants of this age. On the other hand, when infants saw the target

outcome successfully produced by the novel agent, they reproduced it 52% of the

time. Using a Bonferroni procedure to control for inflated P values, a post-hoc

comparison between these two conditions revealed that the infants were signifi-

cantly more likely to produce the target outcome if they first saw it modeled by

the agent (P < .001).

The condition of most interest was the Incompleted Action condition in which

infants saw the agent attempt to produce the target outcomes but fail. In this

condition, infants produced the target outcomes 37% of the time even though

they had never actually seen it achieved. Again, a Bonferroni-corrected compar-

ison confirmed that this rate of target production differed significantly from that

in the Baseline condition (P < .001). The Completed and Incompleted conditions

did not differ from each other.

The percentages of infants in each condition who produced at least one of the

target outcomes were also calculated and are shown in Table 2. About 94% of the

infants (15/16) in the Complete condition produced at least one of the target

outcomes, 80% of the infants (16/20) in the Incomplete condition did so, and only

40% (8/20) in the Baseline condition did (i.e., 60% of the Baseline infants never

spontaneously produced a target outcome on any trial). These results yielded a

significant main effect of condition [c2(2) = 13.73, P < .001]. Pairwise compar-

isons between individual conditions revealed the same pattern of results seen in

Table 1

Mean target actions completed in Meltzoff’s replication with nonhuman agent

Individual objectsOverall mean target

Condition Beads Dumbbell Cap Peg actions per trial

Baseline 0.10 (20) 0.15 (20) 0.16 (19) 0.00 (19) 0.10

Complete 0.75 (16) 0.50 (16) 0.56 (16) 0.27 (15) 0.52

Incomplete 0.47 (19) 0.30 (20) 0.55 (20) 0.16 (19) 0.37

Exact n’s for each cell are shown in parentheses.

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 647

the group averages [Complete vs. Baseline c2(1) = 11.13, P < .001; Incomplete vs.

Baseline c2(1) = 6.67, P < .01; and Complete vs. Incomplete c2(1) = 1.40, n.s.].

Overall, these results replicate the patterns seen in Meltzoff’s (1995) original

reenactment paradigm. Not only were infants able to reproduce the same literal

outcomes of a series of actions produced by an agent on objects but they were

also able to produce the same target outcomes even when the agent tried but

failed to produce them himself. As argued by Meltzoff, this suggests that the

infants interpreted the agent’s actions in terms of the agent’s goals rather than the

spatiotemporal characteristics of the movements themselves.

3. Discussion

One major difference sets these results apart from Meltzoff’s. The goals in this

study were assigned to a nonhuman agent. This was true despite the fact that

infants are known to distinguish between people and nonpeople — as documented

by measures of attention, smiling, vocalizing, and reaching — even when the

nonhuman objects are perceptually or behaviorally similar to people as in the case

of dolls, animals, and contingently behaving robots (Legerstee, 1994, 1997;

Legerstee et al., 1987; Poulin-Dubois et al., 1996; Ricard & Allard, 1993). This

result therefore supports the prediction based on Johnson et al.’s (1998) claim that

infants attribute mentalism broadly, based on both the morphological and

behavioral features of objects — in this case, the presence of a face and hands,

self-generated movement, and contingent interactions with other social agents. It

is at some variance to Meltzoff’s (1995) claim that infants restrict their mental state

attributions to people. Nonetheless, both views agree that when infants reproduce

an unseen target action, they do so based on the attribution of a goal to the actor.

As with all paradigms searching for nonverbal evidence of mentalistic

reasoning, however, alternative explanations exist for the mentalistic interpreta-

tion of the goal reenactment paradigm. These alternative explanations are based

on very different underlying mechanisms than those found in the gaze-following

case but are nonetheless applicable to the novel agent in the current study. The

leading alternative in this paradigm is an explanation based on a combination of

stimulus enhancement and object-based ‘‘affordances.’’ In short, the social agent

serves to direct the infant’s attention to the object, who can then discover the

Table 2

Number of infants completing target actions in Meltzoff’s replication with nonhuman agent

Total number of infants

Condition Never completed target actions Completed one or more target actions

Baseline 12 (60) 8 (40)

Complete 1 (6) 15 (94)

Incomplete 4 (20) 16 (80)

Percentages shown in parentheses.

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656648

target outcomes herself, based on the objective, discoverable properties of the

object. Meltzoff (1995) discussed this alternative at length and included a fourth

condition to control for the effects of both. In his version, infants saw the agent

manipulate the object in an undirected way. If infants’ performance in the

Incomplete condition were based on the combined effects of attentional enhance-

ment and object discovery, they should have performed just as well in this case.

However, they did not. In fact, they performed no differently in this condition

than they did in the Baseline spontaneous play condition. Nonetheless, alternative

versions of the counterarguments can be made based perhaps on fine-grained

analyses of attentional enhancement or the priming of action-based schema. As

with gaze-following, compelling evidence against all possible forms of a non-

mentalistic view is difficult (if not impossible) to generate from within the

paradigm. Therefore, it is still somewhat possible that the novel agents in both the

original gaze-following and the current goal reenactment paradigms elicit

‘‘successful’’ attributions for different, independent, and completely nonmental-

istic reasons.

The original motivation behind testing infants’ interpretations of nonhumans

in this goal reenactment paradigm (after the earlier gaze-following study by

Johnson et al., 1998) was to block just such paradigm-specific arguments.

Therefore, following the logic of collecting multiple behavioral measures, an

additional analysis was performed on the current videotapes — measuring the

infants’ nonverbal communicative gestures (Bates et al., 1975; Bretherton et al.,

1981; Tomasello, 1995) toward the novel object.

We reasoned that if infants were producing the target outcome in the

Incomplete condition because they interpreted the orangutan as a mentalistic

agent with goals, then they should also interact with it as a mentalistic agent (in

all three conditions). Alternatively, if the infants’ performance was based on

attentional enhancement and object discovery alone in the absence of mentalistic

attributions to the agent, they would not attempt to wave to it, show it toys, offer

it toys, make requests of it, or socially reference it (that is, alternate their own

gaze between it and the toys). Indeed, informal coding of the infants in Study 1

revealed that the majority of infants in all three conditions directed some sort of

social/communicative behavior at the agent at least once, including waving,

showing or giving objects, requesting objects, or alternating attention between

the agent’s face and a toy. This finding is consistent with the interpretation that

infants produced the target actions in the Incompleted Action condition, because

they viewed the orangutan as an agent with unfulfilled goals.

However, before the production of these communicative gestures can be taken

as converging evidence of a mentalistic attribution, one further alternative

explanation must be ruled out. Infants in the goal reenactment study received

a great deal of verbal and behavioral support from the experimenter over the

course of the procedure. The experimenter facilitated the infant’s interaction with

the novel agent by introducing them, passing objects back and forth between

them, and in general modeling a mentalistic interpretation of the agent by

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 649

directing communicative acts at it (talking, waving, giving objects, requesting

objects, etc.). Given infants’ propensity to imitate at this age, it is possible that

what appeared to be self-induced communicative gestures directed at the agent

by the infant were in fact merely instances of the infant imitating the exper-

imenter’s behavior toward the object. Note, however, that this explanation

applies only to the infants’ communicative gestures and cannot account for the

infants’ tendency to reenact the agent’s unseen and unachieved goals since the

experimenter herself never attempted any object manipulations.

To rule out this possibility, a faceless and handless surrogate for the agent was

created that the experimenter could direct communicative acts toward but that

would not respond.

4. Study 2

4.1. Method

4.1.1. Participants

Twenty-four 15-month-olds (M= 15 months 15 days; range 15 months 2

days–15 months 30 days) were tested in two conditions based on a modified

version of the Baseline condition of the goal reenactment study, an Agent

condition (n = 11) and a Surrogate condition (n = 13).

4.1.2. Materials

In the Agent condition, the orangutan from Study 1 was used. It was thus

capable of contingent and reciprocal action with both the experimenter and infant

as well as perceptually guided behavior and possessed the morphological features

of both a face and hands. It also necessarily exhibited self-generated and

biologically real movement. In the Surrogate condition, a new object was designed

that was roughly perceptually and morphologically similar to the orangutan

(Fig. 1) but incapable of self-generated movements of any sort — contingent,

reciprocal, perceptually guided, or biologically real. The surrogate was created by

covering a common table lamp of approximately the same size and proportions as

the orangutan with padding and a soft reddish-brown fabric. Like the orangutan,

it sat 18 in. high and 12 in. wide. A set of visually complex black and brown

features were attached to the lamp’s otherwise white shade in lieu of a face, and a

small, black, operational turntable was attached to the base of the lamp in lieu of

manipulatible hands. Thus, for the most part, both novel objects were soft

reddish-brown shapes, with black and white peripherals.

4.2. Procedure

Infants were guided through a prescribed interaction with either the agent or

surrogate. In both conditions, the experimenter talked throughout the procedure

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656650

to the agent/surrogate as though it were a real mentalistic agent. In order to

maintain equal levels of attention-getting activity across the two conditions, each

‘‘active’’ event produced by the orangutan as a self-generated response to the

experimenter or situation was matched by a ‘‘passive’’ event produced by the

experimenter on the lamp.1

4.2.1. Waves

First infants were introduced to the agent/surrogate by name (‘‘Tang’’ for the

orangutan and ‘‘Bob’’ for the lamp) and invited to wave to it. In the Agent

condition, the orangutan waved to the infant in response. In the ‘‘passive’’

condition, the experimenter turned the lamp’s light on and off (and then removed

her hands quickly in order to minimize the time they appeared in the visual field

around the lamp’s ‘‘head’’).

4.2.2. Offers and requests

After their introduction to the agent/surrogate, infants exchanged each of the

four toys with the agent/surrogate (see Study 1 for a description of the toys). At

each exchange, the infant was first asked by the experimenter to either give or

take the object directly from the agent/surrogate. The orangutan was capable of

accepting and passing the object itself. However, because the lamp was not

capable of doing this, in order to keep the experimenter’s participation as

comparable as possible in the two conditions, the experimenter mediated the

exchange in both cases, each time directing her own request or offer gesture at

the agent/surrogate. (It was possible to keep this intervention natural-appearing in

the Agent condition by seating the orangutan far enough away from the infant

that the infant and orangutan could not reach each other in any case). When the

agent received the toy, he held it and turned it over in his hands for 20 s as in the

Study 1 Baseline condition. Again, because the surrogate had no hands with

which to manipulate the toy, in order to maintain the attention-getting activity

level across the two conditions, when the surrogate ‘‘received’’ the toy, the

experimenter placed it on the turntable and spun it, again withdrawing her hands

as quickly as possible.1

4.3. Results

Two independent raters coded the infants’ communicative and social

behaviors into five categories based on general behavioral characteristics

1 It is important to note that although the passive events in the surrogate’s script were physical

rather than psychological events, we do not believe that this constitutes a confound. This is because

physical actions on agents are not considered category mistakes and are not by themselves cues to

category membership. People touch each other, push each other, and pull each other’s hair or clothing.

Such actions are not taken as evidence that the recipient is not an agent or that the actor does not

conceive of the recipient as an agent. Infants’ reactions to these scenarios were recorded on videotape.

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 651

and direction of gaze. The five categories were Greetings, Offers, Requests,

Gaze Alternation, and Withdrawals. Greetings were counted anytime the infant

lifted the fingers of the hand toward the agent/surrogate in a wave-like motion

while simultaneously looking at the agent/surrogate. Offers were counted each

time the infant held an object out toward the agent/surrogate while simulta-

neously shifting her gaze from the object to the agent/surrogate. Requests

were credited to the infant each time she extended her empty hand toward the

agent/surrogate as the agent/surrogate possessed the object while simultane-

ously shifting her gaze from the object to the agent/surrogate. A Withdrawal

was credited each time the baby actively pulled back from the agent/surrogate

by arching her back or pulling in her hands while glancing at least once at the

agent. Finally, a single act of Gaze Alternation with the agent/surrogate was

credited anytime the infant shifted her gaze from the object to the agent/

surrogate in the absence of other gestural actions. The two coders reached

93% agreement.

The sex of the infants had no effect on the results of a preliminary analysis and

will not be discussed further. As seen in Table 3, infants were quite unlikely to

direct these gestures at the passive lamp, despite the fact that the experimenter

herself both directed gestures at the lamp and talked to it in a communicative

manner. An analysis of variance with condition and gesture as variables showed

that infants were much more likely to produce the target behaviors in the presence

of the contingently behaving orangutan than they were in the presence of the

lamp [F(1,22) = 22.26, P < .0001]. Furthermore, this result held even when the

disproportionately frequent gaze alternation behaviors were removed from the

analysis [F(1,22) = 10.03, P < .005]. It appears therefore that infants’ communi-

cative interactions with the orangutan agent, both in this study and in Study 1,

were probably due to infants’ interpretation of the agent itself and not to imitation

of the experimenter’s behavior.

5. General discussion

It was hypothesized that by the beginning of the second year, (1) infants’ have

the ability to attribute mental states to others and (2) that this ability is not

restricted to people. Furthermore, it was argued that the degree to which

putatively mentalistic attributions can be elicited across multiple behavioral

Table 3

Mean number of communicative/social gestures per infant directed at the novel objects in Study 2

Behaviors

Condition Greetings Offers Requests Gaze alternation Withdrawal

Orangutan 2.36 2.09 0.54 11.91 0.82

Lamp 0.92 0.38 0.15 3.31 0.00

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656652

contexts by novel, nonhuman agents is evidence for a central conceptual

representation of mentalistic being, intermediary in the processing stream

between perception and action.

To this end, two studies were conducted in which 15-month-old infants were

presented with a novel object that either did or did not embody mentalistic cues

and invited to treat that object as a mentalistic agent. In Study 1, 15-month-olds

were presented with a novel agent in the form of a colorful stuffed orangutan

animated by an unseen puppeteer. Infants who saw the novel agent perform

object-directed actions (e.g., place beads inside a cup) reproduced those actions

and their outcomes when given the opportunity to play with the objects

themselves. Similarly, when infants who saw the agent ‘‘try’’ but fail to achieve

the same set of target outcomes were given the toys, they produced the inferred

target outcome rather than the actually witnessed spatiotemporal event. In both

cases, the rate of production of the target outcome was significantly higher than

that produced in a spontaneous play baseline during which infants nonetheless

interacted in the same way with the agent and watched it manipulate the toys

(though only after they themselves had had a chance to). Following Meltzoff

(1995), we interpret this pattern of findings as evidence that the infants attributed

goals to the agent; in this case, an animated, stuffed orangutan. We further argue

that the reason infants attributed goals to the nonhuman agent in these studies,

but not to the mechanical pincers in Meltzoff’s original study, is because

Meltzoff’s pincers embodied none of the features that are thought to characterize

mentalistic agents such as the ability to interact contingently with others or the

presence of a face.

Of course, taken alone, these data do not fully block alternative explanations

of the infants’ performance. Like Meltzoff’s original data on 18-month-olds’

imitation of adults, we need not attribute mentalistic interpretations to the child in

order to explain their behavior. If this were the only evidence offered, we might

be unable to eliminate an explanation of the behavior based on the spatiotemporal

trajectories of the movements, the social enhancement properties of people (or

animated apes), or the child’s own exploratory interest in and representations of

objects and the actions they support. Meltzoff blocked (1) the spatiotemporal

arguments with his pincer condition, (2) the social enhancement objection with a

non-goal-directed human manipulation condition, and (3) the object-discovery

objections with a baseline measure of spontaneous target action productions (or a

combination of all three).

We concur with all of those arguments and add an additional one of our own

based on the finding that the infants in our studies also directed communicative

gestures toward the agent. Infants in all three conditions of Study 1 directed

social communicative gestures at the novel agent, including waves hello and

goodbye, requests for toys the agent was holding or offers to give it a toy the

child was holding, and frequent social referencing — alternation of gaze between

the object and the agent. Study 2 confirmed that infants’ communicative gestures

towards the agent were not merely the result of imitation of the experimenter’s

S.C. Johnson et al. / Cognitive Development 16 (2001) 637–656 653

communicative behavior. Infants directed significantly fewer greetings, offers,

and requests towards a surrogate that grossly resembled the orangutan but

embodied no mentalistic diagnostic cues, even though the experimenter directed

communicative acts toward it such as talking and waving to it as well as offering

and requesting toys from it.

The addition of these two productive behaviors, the reenactment of unseen

goals and communicative gestures, to the existing case of gaze-following

(Johnson et al., 1998) strengthens the argument that infants of this age have

access to a conceptual representation of mentalistic agent, intermediary in the

processing stream between perception and action. In addition, we know from

other research that infants distinguish between people and nonpeople, as

documented by measures of attention, smiling, vocalizing, and reaching, even

when the nonhuman objects are perceptually or behaviorally similar to people as

in the case of dolls, animals, and contingently behaving robots (Legerstee, 1994,

1997; Legerstee et al., 1987; Poulin-Dubois et al., 1996; Ricard & Allard,

1993). Therefore, it seems likely that, at least by 15 months, infants have a

representation of mentalistic agent and it is not isomorphic with their repre-

sentation of people.

Acknowledgments

We thank Craig Glasgow, Nicole Peditto, Demmler Schenk, Erika Sockaci,

and Janine Wilmer for help with data collection and coding. This research was

supported by grants to the first author from the National Science Foundation

(#SBR-9709527) and the University of Pittsburgh’s Central Research Develop-

ment Fund and the Faculty of Arts and Sciences Faculty Grants Program.

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