The term imitation
has been used descriptively and theoretically to characterize a broad
range of animal behavior from physical antipredatory adaptations such as
eye spots, which are totally under genetic control, to the human capacity
for the exaggeration of individual characteristics, know as caricature,
which are largely under cognitive control. In the present review many
behaviors that have been called imitative are described, and are
distinguished from "true imitation." It is suggested that at
much of the ambiguity in the literature as to what should be called
imitation can be attributed to the distinction between the function of
imitation and the mechanisms responsible for it. Finally, the various
mechanisms that have been proposed to account for true imitation are
presented and an attempt is made to evaluate them.
the term imitation is used by psychologists it typically implies more than
the simple reproduction of behavior. Imitation carries with it the
implication of intentionality or purposiveness. When humans use the
term to describe their own behavior, it implies that there is an
understanding of the relation between that behavior and the behavior being
modeled (or demonstrated). For example, when a child imitates the behavior
of an adult, one assumes that the child understands that the two behaviors
match (see photo to left). According to Freud (1933), imitation forms an
integral part of the process of identification, and it is motivated by the
need to identify (e.g., with the same-sex parent). But when we look
for imitative learning in animals we must first pare away the mentalistic
terms often used to describe and explain it, and then identify and rule
out simpler mechanisms that might be involved in reports of its
The purpose of this chapter
is first to classify the various cases of social influence depending on
what mechanisms are thought to underlie them. For example, among the
simplest kinds of social influence are those social behaviors that are
typical of the species and that happen to occur in unison (e.g.,
schooling, flocking, and herding). These behaviors can be thought of as
genetically predisposed. Other behaviors may be made more likely to occur
whenever there is an change in the motivation of the observer, and the
mere presence of another animal may have a motivational effect on the
observer. Still other behaviors may occur because the demonstrator or
model can serve as a salient discriminative stimulus that predicts the
appearance of food and allows for an account based on simple associative
learning. It is also possible for the behavior of a demonstrator to
draw the observer’s attention to a location or to a stimulus that is the
focus of the target behavior (e.g., a bar that must be manipulated) and
the observer’s mere proximity to that location or stimulus may make the
target behavior more probable. Finally, it is possible for the behavior of
the observer to have an effect on the environment such that the observer
can learn how objects in the environment work. For example, seeing a door
open outward rather than inward. In some cases more than one simpler
mechanism may be involved. In many cases it may not be possible to
detect the presence of true imitative learning because of the potential
presence of other simpler accounts. After addressing each of these
classes of social influence in turn, we will identify procedures that may
separate them from what has come to be called true imitation.
A second purpose of this
chapter is to distinguish between the function of imitation for the
survival of the organism and mechanisms involved in its use. The
implication of this analysis is that social learning in general and
imitation in particular may be more wide spread than previously thought.
Finally, an attempt will be made to identify the mechanisms by which
organisms are able to imitate.
The broad use of the term
imitation extends to any influence that an organism may have on another
that results is a similarity of behavior or appearance between the two.
Because biologists typically take a genetic approach to the study of
organisms, for them, both physical appearance and behavior have
evolutionary bases and thus, are closely related.
Mimicry. When imitation involves copying of the physical
appearance of one species by another, it is generally referred to as mimicry.
Which is the
When a relatively defenseless animals takes on the appearance of an
animal that has better defenses, it is known as Batesian (or Mertensian)
mimicry. The best known case of Batesian mimicry is that of the
palatable viceroy butterfly (left photo) mimicking the unpalatable monarch butterfly
(right photo, Turner, 1984).
A special case of mimicry involving behavior is the broken-wing
display of the ground-nesting killdeer and avocet (Sordahl, 1981). When
the female bird is near the nest and a predator approaches, the bird
flies away from the nest while mimicking the erratic flight pattern that
might be shown by a bird with a broken wing.
Contagion. When two or more animals engage in similar behavior and that behavior is
species typical, the term
contagion is often used (Thorpe, 1963; also called mimesis, Armstrong,
1951, or response facilitation, Byrne, 1994). Contagion can be used
to describe certain courtship displays when they involve coordinated
movements between the male and female that are can sometimes appear to be
virtual mirror images (Tinbergen, 1960). Also, antipredatory
behavior can be considered contagious when it involves the coordinated
movement of a group of animals for defensive purposes. Such behavior
occurs in certain mammalian (herding) and avian (flocking) species.
When this coordinated behavior is aggressive (i.e., directed toward rather
than away from danger), it is known as mobbing (Hoogland & Sherman,
1976). Contagion can also be shown in an appetitive context. A
satiated animal in the presence of food will often resume eating upon the
introduction of a hungry animal which begins eating (Tolman, 1964). In
the case of contagion, the behavior of one animal appears to serve as a
releaser for the unlearned behavior of others (Thorpe, 1963). For this
reason, most research on animal imitation has used arbitrary, novel,
to-be-acquired behavior as the focus research.
When imitative behavior is
typically studied, an observing animal (e.g., a rat) is exposed to a
demonstrator (rat) that is performing a novel response such as bar
pressing and the rate of acquisition of the novel response is taken as a
measure of imitation. But because rate of acquisition is a relative
measure (it will depend on a variety of procedural factors unrelated to
the conditions of observation), it must be compared with that of a control
group. The choice of control group often depends on the way the
experimental questions are asked. For example, early research
appeared to assume that rats could learn through observation of the
performance of a demonstrator, and the question was, did such learning
occur more quickly than the more typically used experimenter-trained
shaping procedures (i.e., by successive approximations; Corson, 1967;
Jacoby & Dawson, 1969; Powell, 1968; Powell & Burns, 1970; Powell,
Saunders, & Thompson, 1969). The experimental question asked appears
to have been a practical one: Would observation of the demonstration of a
response be a faster means of training rats to bar press. The
problem with the use of a “shaped” control group is that the
procedures used to shape animals to bar press are difficult to specify in
ways that can be accurately reproduced. Furthermore, comparison of
the rate of bar-press acquisition by an imitation group with that of a
group of shaped animals may indicate little about the ability of animals
to imitate, especially if the imitation group acquires the response at the
same rate as, or slower than, the control group. To ask about the
ability of animals to acquire a response through observation of a
demonstrator, a more appropriate control group would be a
“trial-and-error” control (i.e., a group of animals that acquires the
response on its own).
facilitation. The implication of imitative learning is
that information transmitted from the demonstrator to the observer has led
to facilitated acquisition. There is evidence, however, that the
mere presence of an animal (of the same species, i.e., a conspecific) can
have effects on the motivational state of an observer (Zajonc, 1965), and
that changes in the observer’s motivational state can affect the
acquisition and performance of a response (Zentall & Levine, 1972;
Levine & Zentall, 1974). Zajonc has referred to this effect of the
“mere presence” of a conspecific on motivation as social facilitation,
and he has proposed a version of Hull’s (1943) theory to account for the
variety of findings of behavioral
facilitation and inhibition that have been reported in humans and animals.
According to Zajonc, the presence of a conspecific leads to an increase in
arousal which can actually lead to the retardation of acquisition of a
novel (to-be-learned) response. Others have suggested that the mere
presence of a conspecific will facilitate the acquisition of a new
response for the same reason (Gardner & Engel, 1971) or because the
conspecific may have the ability to reduce fear in the observer
& Mason, 1955; Morrison & Hill, 1967). In any case,
experiments concerned with true imitative learning must include a control
for the possibility of facilitation or retardation of response acquisition
resulting from mere presence effects.
One further potential source
of demonstrator-provided motivation should be mentioned here. Although the
mere presence of a conspecific may contribute to the motivational state of
an observer, general (nonspecific) activity may make an additional
contribution. Being in the presence of an active conspecific (i.e.,
one that is working for food but that is responding in a way that is
irrelevant to the target response) might constitute an even better control
than mere presence. We will return to this point later.
motivation. Reinforcement provided to the observer during
the demonstration of a novel response (i.e., incentive motivation) may
also play a role in the rate at which a novel response is acquired.
Although Del Russo (1971) did not find significant evidence for imitative
learning by rats that observed a demonstrator bar pressing for food
(relative to a trial-and-error control) he did find significant
facilitation of bar pressing by a group of observers that got fed whenever
their bar-pressing demonstrators got fed. This facilitation may have
involved a general increase in arousal on the part of the reinforced
observer or a more specific association of the apparatus context with
reinforcement. In either case, the observers would likely have been
more active following observation than the nonreinforced comparison
groups, and more active animals would be more likely to make accidental
contact with the bar.
of aversive conditioning. The imitation of a novel
response being acquired or being performed by a demonstrator that is
motivated by the avoidance of painful stimulation (e.g., electric shock)
presents the need for special control. Emotional cues provided by a
conspecific either escaping from or avoiding shock may provide emotional
cues of pain or fear that could instill fear in an observer. For
example, John, Chesler, Bartlett, and Victor (1968) found that cats that
had observed a demonstrator being trained to jump over a hurdle to avoid
foot shock learned the hurdle-jumping response faster than controls that
did not observe the demonstrators. It may be, however, that being in
the presence of a cat being shocked was sufficient to increase the
observers’ fear (motivation) associated with the conditioning context.
Under such conditions, a change in motivation may facilitate acquisition.
Under different conditions,
however, although rats that observed a trained demonstrator that had
acquired a discriminated shuttle avoidance response acquired that response
faster than rats that observed a merely present demonstrator, rats merely
exposed to the empty shuttle box acquired the shuttle response fastest (Sanavio
& Savardi, 1980).
to sort out mere presence and emotional motivational effects from learning
effects can be quite complex. Although using well-trained
demonstrators can reduce the likelihood of pain-produced cues being
transmitted to the observers (Del Russo, 1975), it may not be possible to
avoid the effects of demonstrator-provided, fear-produced cues
One way to avoid problems
associated with differential motivational cues encountered with
observation of aversively motivated conditioning is to include an
observation control group exposed to performing demonstrators but with the
observer's view of a critical component of the demonstrator's response
blocked. Such a control was included in an
experiment by Bunch and Zentall (1980) who used a candle flame avoidance
task originally developed by Lore, Blanc, and Suedfeld (1971). Bunch and
Zentall found that rats learned the candle-flame-avoidance task faster
after having seen a demonstrator acquire the task, as compared with (1) a
group for which a small barrier was placed in front of the candle such
that the observer's view of the rat's contact with the candle was blocked
and (2) a social facilitation control group (see
Figure 3.). Thus, although a variety of auditory cues (a
potential by-product of the demonstrator's pain), olfactory cues (e.g.,
potentially produced by singed whiskers, defecation, and urination), and
visual cues (e.g. seeing the demonstrator approach and then rapidly
withdraw from something directly behind the barrier) associated with the
task should have provided comparable motivational cues to these control
observers, task acquisition was not facilitated as much as for observers
that could also observe the demonstrator's contact with the candle.
Another means of controlling
for potential motivational cues provided by the demonstrator performing a
pain- or fear-motivated task, is to expose the observers to demonstrators
performing a discrimination (Kohn, 1976; Kohn & Dennis, 1972). In this research, rats that observed a demonstrator performing a relevant
shock-avoidance discrimination acquired that task faster than controls for
which the demonstrator's discrimination was the reverse of the observer's
(i.e., what was correct for the demonstrator was incorrect for the observer
and vice versa).
Although it may be difficult
to control for the social transmission of motivation produced during the
acquisition or performance of an avoidance response, it may be that social
learning is more likely to occur under conditions of fear motivation
because of its greater evolutionary value.
When the observation of a
demonstrator merely draws attention to the consequences of a response
(e.g., a lever press), it may merely alter the salience of the lever
(stimulus enhancement) or the place in the environment where the lever is
located (local enhancement).
Enhancement. Local enhancement refers to the facilitation
of learning that results from drawing attention to a locale or place
associated with reinforcement (Roberts, 1941). For example,
(1935) noted that ducks enclosed in a pen may not react to a hole large
enough for them to escape unless they happen to be near another duck as it
is escaping from the pen. The sight of a duck passing through the
hole in the pen may simply draw attention to the hole. Similar effects can
be demonstrated with Japanese quail.
Local enhancement has also
been implicated in the finding that puncturing the top of milk bottles by
great tits spread in a systematic way from one neighborhood to another
(Fisher & Hinde, 1949). Although the technique of pecking
through the top of the bottle may be learned through observation, it is
also likely that attention was drawn to the bottles by the presence of the
feeding birds. Once at the bottles, the observers found the reward
and consumed it. Learning to identify milk bottles as a source of
food, can readily generalize to other open bottles. Finally,
drinking from opened bottles can readily generalize to an attempt to drink
from a sealed bottle, which in turn can lead to trial-and-error puncturing
of the top.
Local enhancement may be
studied in its own right. As Denny, Clos, and Bell (1988) have
shown, observation by rats of merely the movement and sound of a bar being
activated (by the experimenter from outside the chamber) and paired with
food presentation can facilitate the acquisition of the bar press
response, relative to various control procedures.
Local enhancement may also
account for John et al.'s (1968, Exp. 2) finding of socially facilitated
acquisition of lever pressing by cats. Cats placed in the same
chamber as another cat lever pressing for food, learned to press that
lever faster than other cats that observed another cat that was fed
periodically without lever pressing. But observation of lever
pressing may simply draw attention to the lever. Local enhancement
is especially likely in this context, in which observation of the moving
lever might encourage lever approach upon removal of the demonstrator
(especially by a species known for its motivation to explore).
Similarly, local enhancement
may play a role in the faster acquisition of lever pressing by kittens
that observed their mothers as demonstrators, than by kittens that
observed a strange female demonstrator (Chesler, 1969), because
orientation towards the mother may be more likely than towards a strange
Local enhancement may also
be involved in John et al.'s (1968, Exp. 1) finding of facilitated
acquisition of an aversively motivated hurdle jump response. The
distinction between true imitation and local enhancement may be a subtle
one in this case, but observation of the demonstrator simply may draw the
observer's attention to the top of the hurdle. In other words,
seeing a ball bounce over the hurdle, or even placing a flashing light at
the top of the hurdle might be enough to facilitate the hurdle jumping
response. In general, whenever the performance observed involves an object
(i.e., a manipulandum) to which the observer must later respond, local
enhancement may play a role (Corson, 1967; Denny, Clos, & Bell, 1988;
Herbert & Harsh, 1944; Jacoby & Dawson, 1969; Oldfield-Box, 1970).
In other cases, it may be
possible to control for local enhancement effects by including proper
controls.Lefebvre and Palameta (1988), for example, found that
pigeons that observed a model pierce the paper cover on a food well to
obtain hidden grain, later acquired that response on their own, whereas
those that observed that same response, but with no grain in the well (the
model performed in extinction), failed to acquire the response.
Enhancement. In the case of local enhancement, the
attention of an observer is drawn to a particular place by the activity of
the demonstrator. The term stimulus enhancement is used when the
activity of the demonstrator draws the attention of the observer to a
particular object (e.g., the manipulandum). Quite often in the study
of imitative learning, the object in question is at a fixed location so
the two mechanisms are indistinguishable. In the duplicate-chamber
procedure (see Warden & Jackson, 1935; Gardner & Engel, 1971),
however, a manipulandum (e.g., a lever) is present in both the
demonstration chamber and in the observation chamber.Under these
conditions, drawing attention to the demonstrator's lever should not
facilitate acquisition of lever pressing by the observer. In fact,
one could argue that it should retard acquisition of lever pressing by an
observer because it should draw the observer's attention away from its own
lever. In the case of stimulus enhancement, however, the similarity
between the demonstrator's lever and that of the observer may make it more
likely that the observer notices its own lever after having its attention
drawn to the demonstrator's lever. Thus, stimulus enhancement refers
to the combination of a perceptual, attention-getting process resulting
from the activity of the demonstrator in the presence of the lever, and
stimulus generalization between the demonstrator's and observer's levers.
Because it subsumes local enhancement effects, the term stimulus
enhancement may be more inclusive and thus, may be preferable (Galef,
Stimulus enhancement may
also be involved in the facilitated acquisition of an observed
discrimination. If the demonstrator is required to make contact with
the positive stimulus, but not the negative stimulus, the positive
stimulus is likely to attract the observers attention and responding to it
may be facilitated (Edwards, Hogan, & Zentall, 1980; Kohn, 1976; Kohn
& Dennis, 1972; Fiorito & Scotto, 1992; Vanayan, Robertson, &
Stimulus enhancement may
also play an important role in mate-choice copying by guppies (Dugatkin,
1996). Female guppies that see a model female in the presence of a
courting male will prefer that male over an alternative male (Dugatkin,
1992; Dugatkin & Godin, 1992).
The facilitation of learning
through perceptual factors presents a most difficult problem for the study
of imitation in animals. If the similarity between the
demonstrator’s location or manipulandum and that of the observer
presents an interpretational problem because of perceptual factors, making
the location or the nature of the manipulandum for the observer different
from that of the demonstrator is likely to interfere with the observers
“understanding” of the relation between the two tasks. This
problem, which will be addressed later, will require a new approach to
defining adequate control procedures.
There are a number of cases
of social learning which may be mediated by simple nonsocial learning
mechanisms. Although social stimuli are present and those social
stimuli may play a role in facilitating acquisition of the target behavior
(perhaps because the social stimuli are more salient than nonsocial
alternatives), the mechanisms by which the observer acquires the behavior
may be more parsimoniously explained in terms of simpler species-typical
or individual learning processes.
Imprinting.The first example of social learning that should be distinguished from
true imitation is imprinting. Imprinting
is a process that occurs primarily in species which do not have the luxury
of a nest or den in which to protect their young. In such species
(e.g., fowl and grazing mammals), the young are hatched (or born) in
a precocious state that allows them to move about following a very brief
period of inactivity. To compensate for their mobility (which could
also put them a great risk of predation) most of these species have
evolved the predisposition to follow the first moving object they see.
Although this object is generally their mother, laboratory experiments
show that almost any moving object can function as the object of
imprinting (Hess, 1973).
Imprinting is a curious
process that combines a strongly predisposed behavior (following) with
considerable flexibility (learning) in the nature of the object that is
followed. Although one could say, in a very general sense, that the
imprinted young are imitating the mother, the act of following (or
approach), is more parsimoneously interpreted as a simple conditioning
process, with fear reduction serving as the reinforcer (Kovach & Hess,
following (or matched dependent) behavior.Rats can learn to
follow a trained conspecific to food in a T maze in the absence of any
other discriminative stimulus (Bayroff & Lard, 1944; Church, 1957;
Haruki & Tsuzuki, 1967). Although the leader rat in these
experiments is clearly a social stimulus, the data are more parsimoniously
interpreted in terms of simple discriminative learning. If, for
example, the demonstrator were replaced with a block of wood pulled along
by a string, or even an arrow at the choice point directing the rat to
turn left or right, it is clear that one would identify the cue (i.e., the
demonstrator, the block of wood, and the arrow) as a simple discriminative
stimulus. Even if following a demonstrator led to faster learning
than following a passive signal, it might merely indicate that the social
cue was more salient than either a static or a moving nonliving cue (see
Stimbert, 1970). For matched-dependent behavior to be analogous to
imitation, the untrained animal would have to follow the demonstrator on
the first trial. Even then, however, the motivation to affiliate
could account for following behavior.
conditioning. The observation of a performing demonstrator may
not merely draw attention to the object being manipulated (e.g., the
lever), but because the observer's orientation to the object is often
followed immediately by presentation of food to the demonstrator, a
Pavlovian association may be established. This form of conditioning
has been called observational conditioning (Whiten & Ham, 1992),
valence transformation (Hogan, 1988), or emulation (Tomasello, 1990) in
which the observer learns the relation between some part of the
environment and the reinforcer (e.g., that the top of a box can be removed
to reveal what is inside). Although such conditioning would have to take
the form of higher-order conditioning (because the observer would not
actually experience the unconditional stimulus), there is evidence that
such higher-order conditioning can occur, in the absence of a
demonstrator. If, for example, the onset of a localizable light is
followed shortly by the presentation of inaccessible grain, it is
sufficient to produce pecking by pigeons to the light (Zentall &
Hogan, 1975). The presence of a demonstrator drawing additional attention
to the object to be manipulated (by pecking) and to the reinforcer (by
eating) may further enhance associative processes in the absence of
With regard to the nature of
the conditioning process, it is of interest that when reinforcement of the
demonstrator's response cannot be observed (or the response-reinforcer
association is difficult to make) acquisition may be impaired (Akins &
Zentall, 1997; Groesbeck & Duerfeldt, 1971; Heyes, Jaldow, &
Dawson, 1994). Furthermore, rats appear to acquire a bar pressing
response faster following observation of a bar-pressing demonstrator if
they are fed at the same time as the performing demonstrator (Del Russo,
1971). Although that result was mentioned earlier in the context of
increased motivation on the part of the observer, it is also possible that
feeding the observer following the demonstrator's response may result in
simple Pavlovian conditioning (i.e.,the pairing of bar movement with
may also play a role in an experiment in which observation of experienced
demonstrators facilitated the opening of hickory nuts by red squirrels,
relative to trial-and-error learning (Weigle & Hanson, 1980).
Differential local enhancement can be ruled out, in this case, because
animals in both groups quickly approached and handled the nuts, and the
observers actually handled the nuts less than controls (perhaps because
observers were more efficient at opening them). However, observers
alone got to see the open nuts and they had the opportunity to associate
open nuts with eating by the demonstrator.
preferences (e.g., Galef, 1988a; Strupp & Levitsky, 1984) represent a
special case of observational conditioning. Although food preference
may appear to fall into the category of unlearned behavior subject to
elicitation through contagion, consuming a food with a novel taste should
be thought of as an acquired behavior. The mechanisms responsible
for socially-acquired food preferences appear to have strong simple
associative learning components (e.g., learned safety or the habituation
of neophobia to the novel taste), for which the presence of a conspecific
may serve as a catalyst. Furthermore, these specialized mechanisms
may be unique to foraging and feeding systems.
One of the best examples of
observational conditioning is in the acquisition of fear of snakes by
laboratory-reared monkeys exposed to a wild-born conspecific in the
presence of a snake (Mineka & Cook, 1988). Presumably, the
fearful conspecific serves as the unconditioned stimulus, and the snake
serves as the conditioned stimulus. It appears that exposure to a
fearful conspecific or to a snake alone is insufficient to produce fear of
snakes in the observer. For an excellent discussion of the various
forms of observational conditioning see Heyes (1994).
song. A special case of matching behavior by animals is the
acquisition of bird song (Hinde, 1969; Marler, 1970; Nottebohm,
1970; Thorpe, 1961; see also vocal mimicry; e.g., Pepperberg, 1986;
Thorpe, 1967). Although for many species of song bird the
development of species typical song is regulated to a large extent by
maturation and the seasonally fluctuating release of hormones, regional
variations in the song appear to depend on the bird’s early experience
with conspecifics (Baptista & Petrinovitch, 1984). Thus, one
could say that young song birds learn their regional dialect by imitating
the song of more mature conspecifics.
Acquisition of bird-song
dialect is a special case of imitation for three reasons. First,
although it is learned, bird song is a variation on a species typical
behavior and thus, is relatively constrained. Second, according to
Heyes (1994), in the acquisition of bird song, components of the matching
behavior occur by chance and these components increase in frequency
because they are intrinsically rewarding. Heyes refers to such
behavior as copying rather than imitation. But finally, and most
importantly, bird song takes place in the auditory modality. A
characteristic of auditory events is that the stimulus produced by the
demonstrator and that produced by the “observer” can be a close match,
not only to a third party (i.e., the experimenter) but also to the
observer. Thus, verbal behavior, for which comparisons between one's own
behavior and that of others is relatively easy because one can hear one's
own utterances with relative fidelity, may be a special “prepared”
case of generalized, stimulus identity learning (in which animals that
have been trained to match shapes can now use the principle of matching to
match novel hue stimuli; see Zentall, Edwards, & Hogan, 1983).
Matching. This analysis of the
imitation of verbal behavior can also be applied to certain examples of
visual imitation. Any behavior that produces a clear change in the
environment, such that from the perspective of the observer there is a
match between the stimulus produced by the demonstrator and that produced
by the observer, may be a case of stimulus matching (e.g., observing
someone turning up the volume of a radio - when the knob turns to the
right, the volume increases). Such cases of visual stimulus matching
can be distinguished from the perhaps more abstract and interesting case
in which no visual stimulus match is possible (e.g., the imitation of a
person who has his hands clasped behind his back).
Emulation of Affordances. When observation of a
demonstrator allows an animal to learn how the environment works, a
sophisticated form of learning is certainly involved. But one may not want
to view it as imitation. For example, Bunyar and Huber (1999) allowed
marmosets to observe conspecifics entering a food box through a door
hinged at the top by pulling it towards themselves or pushing it away from
themselves. Observers generally opened the door of the box in the way they
had seen it demonstrated, but could they have learned through observation
‘how the door works’ rather than the movements required to open the
door? Tomasello (1996) has referred to this kind of learning as the
emulation of affordances because it may not require observation of an
animal at all (see also Gibson, 1979). Would the marmosets have learned as
much from having observed the door opening inward or outward by means of
an invisible wire? If so, we would not want to call that learning
imitation. Similarly, interpretation of the results of a number of other
studies is made difficult by the fact that two different behaviors have
two different effects on the environment observed. For example, Custance,
Whiten, & Fredman, (1998) used “artificial fruit” to simulate the shell of fruit that must be removed by
monkeys to gain access to the edible portion inside. In fact,
demonstrators opened a latched clear plastic box in one of two distinctive
ways. Observer monkeys showed a significant tendency to open the box by
the same means as they observed it demonstrated.
Emulation of affordances can
also account for findings of observation learning by Dawson and Foss
(1965). They reported that budgerigars acquired a lid-removal task (by
trial-and-error) in one of three different ways: Pushing the lid off
with the beak, twisting it off with the beak, or grasping it with the foot
and pulling it off. Observers were then exposed to these performing
birds, and when they were then given the opportunity to perform
themselves, each observer removed the lid in same manner as its
demonstrator (see also, Galef, Manzig, & Field, 1986). But moving the
lid in different ways may have provided information about different
affordances. Similarly, Will, Pallaud, Soczka, and Manikowski (1974),
noted a related effect in a study in which rats observed either a trained
demonstrator performing a successive discrimination or an experimentally
naive demonstrator. They found that the trained demonstrators
typically responded with one of three distinctive patterns when the
discriminative stimulus was available and that the observers learned not
only to respond in the presence of one stimulus and not in the presence of
the other, but they also learned the pattern of responding of their
demonstrator (e.g., alternating a bar press with eating, or making a burst
of bar presses followed by eating the accumulated pellets).
Heyes and Dawson (1990) have
reported similar results by rats that observed demonstrators expressly
trained to respond in one of two different ways. After observing
demonstrators push an overhead bar either to the left or to the right,
Heyes and Dawson found that observers given access to the bar tended to
push the bar in the same direction as their demonstrator.
Remarkably, the observers matched the demonstrators' behavior in spite of
the fact that, because the observers faced the demonstrators during the
period of observation, the direction of bar motion (relative to the
observer's body) during observation was opposite that of the bar's motion
when the observers performed. But in this experiment, too, the overhead
bar moved in different directions (toward different walls of the
demonstrator’s chamber) for the two observation groups. It is
unlikely that the movement of the bar to a particular location was solely
responsible for the reported effect, however, because Heyes, Jadlow and
Dawson, (1994, Experiment 2) reported similar effects when the bar was
moved between the time of observation and observer performance from the
common wall between the two chambers to one of the side walls (i.e., a 90o
shift in the direction of possible movement of the bar). However, it is
also possible that olfactory cues, specific to the side of the bar against
which the demonstrators pushed, was responsible for this imitation-like
effect (Gardner & Heyes, 1998; Ray & Heyes, 1998).
True imitation has been
defined as "the copying of a novel or otherwise improbable act or
utterance, or some act for which there is clearly no instinctive
tendency" (Thorpe, 1963, p. 135). The preceding analysis allows
us to be more precise. First, one should control for motivational effects on the observer produced either by the mere presence of the demonstrator or by the mere consequences of the behavior of the demonstrator. Second, one should control for the possibility that the demonstrator's manipulation of an object merely draws the observer's attention to that object (or one like it), thus making the observer's manipulation of the object more probable. Third, one should control for the simple pairing of a novel stimulus (e.g., a lit response key or the movement of a bar) with the presentation of inaccessible food). And finally, for true imitation to be demonstrated, the target behavior should not already be part of the observing animal's repertoire (Clayton, 1978). In practice, however, it is not easy to determine the repertoire of an animal. In fact, one could argue that any behavior that an animal is capable of performing must be similar to a behavior that is already in the animals repertoire. Furthermore, ruling out the prior existence of a behavior requires the acceptance of 'never seen' as absence. Alternatively, one can define the response to be acquired in terms of the relatively low probability of the occurrence of the response in under similar conditions but in the absence of the opportunity to observe a demonstrator performing that response. Imitation is then defined as a relatively large increase in the probability of the demonstrated response, relative that of an appropriate group that controls for all of the already-noted
non-imiative causes of such behavior.
The Two-Action Method and
In a variation on the
procedure used Dawson and Foss (1965), Akins and Zentall
(1996) tried to overcome the problem of differential environmental
consequences by training quail to respond to a treadle for food either
by pecking at the treadle or by
stepping on the treadle. With a common
manipulandum and the common movement of the manipulandum, the effect of
the two response topographies on the environment should be common as
and Zentall found that observers showed a significant
tendency to respond to the treadle with the same part of the body (beak
or foot) as their respective demonstrator (see Zentall, Sutton, & Sherburne, 1996, for similar results
with pigeons. Kaiser, Zentall, and Galef (1997) have found that a combination of trial-and-error learning to step together with contagious pecking was not sufficient to account for these two-action-method results.
Two important points should
be made about this procedure. First, the environmental consequences of
stepping and pecking were essentially the same (i.e., everything was the
same except the two response topographies). And second, it is very
unlikely that there was any similarity between the visual stimulus sen by
the observer during observation and that seen by the observer during its
own performance of the same response. Specifically, the demonstrator’s
beak on the treadle must have appeared quite different to the observer
from the observer’s own beak on the treadle. Similarly, though perhaps
not so obviously, when the quail stepped on the treadle (located near the
corner of the chamber) they pulled their head back and thrust their head
forward. Thus, they could not see their foot making contact with the
treadle. Once again, to the observer, the demonstrator’s response to the
treadle must have appeared quite different from the observer’s own
response to the treadle. Therefore, any account of the imitation found in
these experiments in terms of stimulus matching is quite implausible.
Reinforcement of the
demonstrated response. Earlier it was noted that the pairing of the
movement of a manipulandum with a reinforcer, could increase the
probability of the target behavior because of simple learning effects.
Using the two-action method, the role of simple learning effects can be
examined directly, rather than as an artifact to be avoided. Akins &
Zentall (1998) have recently found that the correspondence between
observer and demonstrator response topography disappears when the
demonstrators responses are not reinforced.
A cognitive account of this finding is that through observation, the
observer learns that there is no positive consequence associated with the
demonstrator’s response and thus, there is no incentive for making the
same response. This interpretation assumes that the lack of
correspondence between observer and demonstrator response topography
results from a performance decrement rather than from a learning
A simpler account of this
finding suggests that with this preparation, an association between the
demonstrator’s behavior and reinforcement is necessary for true
imitation to occur. It does not provide an alternative account of
imitative learning, however, because it cannot account for the
correspondence between the observer’s and demonstrator’s response
topographies. Instead, reinforcement may act as a catalyst to bring out
Motivation of the
If demonstrator reinforcement is necessary for the observer to learn
through imitation, it suggests that observer incentive may play a role in
imitative learning. If observers must be adequately motivated for them to
imitate, it further suggests that the relevance of the demonstrator’s
reinforcer to the state of the observer is also likely to be important. If
this extrapolation from the data reported by Akins & Zentall (1998) is
correct, food sated observers should be less inclined to learn a
food-rewarded response through observation than hungry observers. Dorrance
and Zentall (2001) tested this hypothesis by comparing imitative learning,
using the two-action method, by quail that were either hungry or sated
during observation. In support of the hypothesis, they found that hungry
quail matched the demonstrator’s behavior if they had observed while
hungry but not if they had observed while sated.
Proficiency of the
demonstrator. One might also expect proficiency of the model to
affect the rate of acquisition of the behavior by observing pigeons (Vanayan,
Robertson, & Biederman, 1985). Contrary to expectation, however,
Vanayan et al. found faster acquisition of a successive discrimination by
observers when less proficient models were observed. It may be that
observation of the consequences of incorrect (nonreinforced) responding is
as important (or, in the case of aversively motivated learning perhaps,
even more important) than observation of the consequences of correct
(reinforced) responding. As mentioned earlier, however, observation
of a discrimination being performed may result in stimulus enhancement and
the demonstrator proficiency effects found may result from differential
(1969) has indicated that there is an important difference between
immediate imitation (which he calls imitation) and deferred imitation
which he calls observational learning. For Bandura, immediate imitation
may be a reflexive response that is genetically predisposed (akin to
contagious behavior) whereas deferred imitation is indicative of a more
cognitive process. Although it is possible that pecking and stepping
behaviors could be transmitted via contagion, the fact that the
demonstrated response and the observer’s performance do not occur at the
same time makes that account unlikely to be correct. On the other hand,
critics of this research might be more convinced if evidence could be
provided for imitative learning that can be demonstrated with a
significant delay between observation and observer performance. Such
evidence has been reported by Dorrance and Zentall (2001). As part of a
larger study, Dorrance and Zentall allowed hungry quail to observe either
treadle pecking or treadle stepping. The quail were then returned to their
home cage where they were fed and a half hour later were tested in the
demonstration chamber. Dorrance and Zentall found clear evidence of
imitation that was not distinguishable from that of observers that were
tested immediately following observation. Thus, a half hour delay between
observation and observer performance appears to have little effect on the
expression of imitative learning by quail.
Enculturation. One of the
variables that may play a role in imitative learning by primates appears
to be the degree to which the animals have had extensive interactions with
humans - what Tomasello (1990) refers to as enculturation. Enculturated
chimpanzees and orangutans readily show signs of imitative learning (Tomasello
, Gust, & Froat, 1989; Tomasello, Savage-Rumbaugh, & Kruger, 1993;
Russon & Gladikas, 1993, 1995), whereas lab housed/reared chimpanzees
typically do not (Whiten & Custance, 1996).
Enculturation may produce
its effect in a number of ways. First, it could reduce the apes’ anxiety
during test. Second, it could increases their attentiveness to social
cues. Third, to could give them prior reinforced experience imitating
(i.e., it could allow them to experience a form of learning to learn). A
better understanding of the various components of enculturation might
provide important insights into imitation by apes.
A form of imitative learning
conceptually related to the two-action method occurs when the gestures of
a model are copied. Imitation of gestures has been found in chimpanzees (Custance,
Whiten, & Bard, 1995, Hayes & Hayes, 1952), Dolphins (Harley,
Xitco, Roitblat, & Herman, 1998; Xitco, Harley, & Brill, 1998),
and a parrot (Moore, 1992). Remarkably, especially in the case of the
dolphin and the parrot, the models were human rather than a conspecific.
Thus, there was little similarity between corresponding body parts of the
observer and the demonstrator. Because objects were not involved, local
and stimulus enhancement should be irrelevant. Furthermore, each imitated
gesture serves as a control for the others because it is the topography of
the response that is important. In addition, the broad range of
gestures that have been shown to be imitated within a few seconds of
demonstration suggests that no account based on differential motivation is
likely to play a role.
Imitation of a particular response can be thought of as one example of a
broad class of imitative behavior. One can then ask if an animal can
learn to match any behavior of another "on cue". (i.e.,
can an animal learn the general concept of imitation and then apply it
when asked to do so in a "do-as-I-do" test). Hayes and
Hayes (1952) found that a chimpanzee (Viki) learned to respond correctly
to the command "Do this!" over a broad class of behavior.
More recently, Custance, Whiten, and Bard (1995) have replicated
this result under more highly controlled conditions. Furthermore,
Custance and Bard (1994) using the “do as I do” procedure, have found
that actions on parts of the body that cannot be seen by the performer
were just as readily copied as those that could be seen. The importance of
behavior that cannot be seen by the performer (e.g., touching the back of
one’s head) is that it rules out the possibility that some form of
visual stimulus matching might account for the behavioral match. The
establishment of a “do as I do” concept not only verifies that
chimpanzees can imitate, but it also demonstrates that they are capable of
forming a generalized behavioral-matching concept (i.e., the chimpanzees
have acquired an imitation concept).
Interest in imitation research can be traced, at least in part, to the
assumption that true imitation involves some degree of intentionality.
This is certainly the case in many of the higher order forms of imitation,
such as the human dancer who repeats the movements of the teacher.
Unfortunately, intentionality, because of its indirect nature, can only be
inferred, and evidence for it appears most often in the form of anecdote
rather than experiment. Ball (1938), for example, noted the case of
a young rhesus monkey that, while kept with a kitten, was observed to lap
its water in the same way as a cat. Ball noted further that lapping
is extremely rare in rhesus monkeys. Similarly, Mitchell (1987),
in an analysis of various levels of imitation, provides a number of
examples of imitation at these higher levels. For example, he
discusses the young female rhesus monkey who seeing her mother carrying a
sibling, walks around carrying a coconut shell at a same location on her
own body (Breuggeman, 1973). Such anecdotes, by their
very nature, are selected and are difficult to verify. If there were
some way to bring these examples of intentional imitation under
experimental control, it would greatly increase their credibility.
the highest level of imitative behavior, what Mitchell (1987) refers to as
fifth-level imitation, not only does the behavior of the observer not
match that of the demonstrator, but the differences are explicit and they
are produced for the purpose of drawing attention to certain
characteristics of the model. Examples of such symbolic imitation
can be found in the human use of parody and caricature. Such forms
of imitation are mentioned primarily for completeness and to note the
degree of subtlety that can be involved in imitation.
Although imitation has been
viewed by psychologists as purposive, intentional, and reflective, when
imitation is viewed from the perspective of biological function, it can
take on very different characteristics. These functional
characteristics may account for the broad range of behavior that has been
classified as imitative. For example, rather than viewing imitation
as higher form of learning that requires conceptual ability, Boyd and
Richerson (1988) have examined it in terms of its potential specific costs
and benefits to an organism, as compared with two other evolutionary
strategies: species typical behavior (primarily under genetic control) and
individual (trial-and-error) learning (primarily under control of the
direct consequences of the behavior to the organism).
The benefit of species
typical behavior is its certainty. Birds do not have to rely on
trial-and-error learning to build a nest. They are genetically
predisposed or programmed to build them. On the other hand, there is
a cost to such inflexible behavior. Should the environment change in
a way that is inconsistent with an animal’s predispositions, there may
not be enough flexibility in the system to allow for survival. The giant
panda lives almost entirely on bamboo shoots. There has been little
competition for this resource and thus, there has been little need for the
panda to develop a varied diet. When bamboo is plentiful the panda can
thrive. But with the encroachment of human populations the bamboo
forests have shrunk in size and the panda has become an endangered
allows an animal to adjust to a changing environment. For example,
in an unpredictable environment where ideal foods may not be available or
where others animals may compete for that food, an animal may be
predisposed to follow a more general rule. In humans, the preference
for sweet food is an example of such a rule. When such categorical rules
are insufficient, more arbitrary rules based on individual experience
(learning) may be necessary. For example, many animals (including
humans) are predisposed to follow the rule, “If one encounters a novel
taste, one should eat only a small amount; if one then gets sick, one
should stay away from that taste; if one doesn’t get sick one
should eat more” (see Garcia & Koelling, 1966). Thus, animals
can learn which foods are good to eat and which are not.
But trial-and-error learning
has its cost as well. For an animal to learn what not to eat, it
must sometimes risk the negative consequences. Rats can learn what
foods to eat by trial-and-error but such behavior can result in them
getting poisoned. Learning can be beneficial, but it can also be costly.
According to Boyd and Richerson (1988), social learning may serve an
intermediate role between species typical behavior and individual
trial-and-error learning. If an animal learns from watching another
animal, it can benefit from the trial-and-error learning of the other
without having to suffer the consequences of errors. For example, if
a rat encounters two novel flavors of food, it will prefer the flavor that
it sees another rat eat (Galef, 1988a). Although the mechanism by
which food preference are acquired socially is much simpler than true
imitation, imitative learning may have evolved for similar reasons - it
allows the experience of one individual to be passed on to others more
efficiently than would be the case with trial-and-error learning, yet
retaining much of the flexibility of individual learning.
In human societies, culture
and tradition are the means of passing on the experiences of group members
to the benefit of other members of the group. Individual learning
can last a lifetime, social learning can be passed on for many
generations, but it allows for considerably more flexibility that does
genetically predisposed behavior.
A more functional, inductive
approach to the study of imitative learning may also provide insights into
the conditions under which it would be most likely to occur (see Davis,
1973; Howard & Keenan, 1993). The relatively asocial laboratory
rat or pigeon used in psychological research may not be most appropriate
subject for the study of imitation. Instead, animals with better
visual acuity than the rat and which are more precocious and social than
the pigeon may be more likely to imitate (e.g., the Japanese quail, Akins
& Zentall, 1996).
Although we have argued that
animals that engage in social learning are likely to benefit from it by way
of increased fitness over those than engage in only species typical
behavior and individual learning, not all species may benefit from
imitative learning. Even highly social species that are capable of
considerable behavioral plasticity (in the form of individual learning),
such as monkeys, may not benefit from imitation because of the nature of
resources in their environment. For example, they may be more likely to
find and eat novel food in the presence of others who are eating (Fragazy
& Visalberghi, 1996) but they may not benefit from observing how
others find and eat novel food. Thus, although imitative learning appears
to be maximized in highly social species, it may not be an inevitable
consequence of living in social groups. Imitation appears to be widely
scattered among species, with humans and great apes being the most
prolific imitators, but dolphins and a number of avian species including
parrots, pigeons, and Japanese quail show evidence of imitative learning
as well. Imitation by a number of bird species, together with the relative
absence of imitation in monkeys (Fragazy & Visalberghi, 1989, 1990;
Whiten & Ham, 1992; but see also Custance et al., 1998) suggests that
a high degree of behavioral plasticity and sociality may be neither
necessary nor sufficient for the development of imitative learning.
There has been much
speculation about the meaning of true imitative learning. Some have
described it as a reflective (conscious?) process ( Morgan, 1900) or as
“the purposive, goal-directed copying of the behavior of one animal by
another” (Galef, 1988b, p. 21), whereas others see it as an extension of
simple learning principles (Gewirtz, 1969).
Associative Learning Accounts
The simplest account
of imitation has been provided by social learning theorists (Bandura,
1969; Gewirtz, 1969; Miller & Dollard, 1941). For most social learning
theorists, imitation can be explained as a special case of simple
instrumental learning. Gewirtz, for example, proposed that
initially, when a demonstrator (or model) engages in a particular
behavior, the young observer responds in a variety of ways that are
unrelated to the behavior being modeled. Occasionally, and only by
chance, a correspondence might occur between the behavior of the model and
that of the observer. According to Gewirtz, those instances of
behavioral correspondence are typically accompanied by reinforcement. For
example, a parent may say “daddy” many times to an young child and on
those occasions on which it happens to be followed by “dada” spoken by
the child, positive reinforcement (perhaps socially, through the
parent’s excitement and attention) will often be provided. The word
"daddy" then comes to serve as a conditioned stimulus that
signals the opportunity to obtain reinforcement for emitting the response
"dada." Thus, conditioning theory can explain individual
cases of response copying, especially when verbal behavior is involved.
But every imitated word does not go through such a processes of
reinforcement by successive approximation (i.e., trial-and-error shaping).
To account for the extensive
use of imitative learning by children, Gewirtz (1969) proposed that copied
responses that occur initially through selective reinforcement, come to
generalize to other behavior, without the need for additional consistent
reinforcement. If generalization, as it is used here, is meant to be
explanatory, rather than merely descriptive, however, it requires a more
complex mechanism than simple associative learning can provide.Stimulus generalization theory (Spence, 1937) is based on the principle of
physical stimulus similarity. Specifically, a reinforced response in the
presence of a particular stimulus will tend to occur in the presence of
other stimuli, to the extent that those other stimuli are physically
similar to the training stimulus. But when applied to imitation, how
does an infant generalize from repeating the word "daddy" to
repeating the quite different sounding word "ball"?
Furthermore, the concept of generalization refers to the probability of
occurrence of the trained response, rather than a matching response. Thus,
according to such a conditioning model, the response “daddy” should
occur to other stimuli to the extent that they sound like “daddy.”
imitation may be related conceptually to identity learning with visual
stimuli, but in the case of imitation, it is the matching of behavior
rather than stimuli. When Baer, Peterson, and Sherman (1967) trained
retarded children to match several behaviors of a model when instructed
to, “Do this,” they found that the children continued to match in the
absence of reinforcement. They proposed that the children had formed
a functional stimulus class defined by the correspondence between the
stimulus output of the child’s behavior and the stimulus output of the
model’s behavior. Thus, to account for such stimulus/response matching,
a child must, at a minimum, have a concept of identity (i.e., the child
must understand what it means that two things are the same, see Zentall,
Edwards, & Hogan, 1983) or what Gewirtz (1969) calls a
matching-response class. Such an analysis implies processes that go
beyond simple learned associations and their generalization. But children
do show evidence of identity learning at a very early age (Tyrrell,
Zingaro, & Minard, 1993) and pigeons too show the capacity for
identity learning (Zentall, Edwards, Moore, & Hogan, 1981).
The copying of verbal
behavior may be explained in this way because one can hear one's own
utterances with relative fidelity, and one can compare them directly with
those of a model (i.e., stimulus matching). However, such matching of
response-produced stimuli to target stimuli cannot account for imitation
by a young child when an adult model says, "Do this," as the
model places his hands over his eyes. In this type of imitation,
from the perspective of the observer, there is no match between the
stimulus provided by the behavior of the model and that provided by the
observer’s own behavior.
According to Piaget (1955),
true imitation involves sensory-motor assimilation. It is the
coordination of first, the sensory-motor system of the individual (or the
self), which occurs at an early age and then, an appreciation of the
similarities of between the individual and others. In Piaget’s view,
this process occurs first through the similarity between the seen body
parts of others and the corresponding seen body parts of child. Later, an
acquired cross-modal matching process allows the child to understand the
correspondence between its own unseen body parts (e.g., the eyes, nose,
and head) and those of others. This cross-modal matching process is based
on (1) touch (the felt parts of self and others), (2) the correspondence
of touch and sight (the felt and seen body parts of others), and (3) the
inference that because one’s own unseen body parts feel like those of
others, they must look like those of others. Finally, this assimilation
results in a schema of the individual (i.e., an image, in our mind’s
eye, of ourselves). In explaining the development of imitation in
children, Guillaume (1971) views imitation as linked to the child’s
notion of self and he proposes that “imitation enables the child to see
himself in the person of another” p. 207. Thus, according to this
view, the mechanism that makes imitation possible is the ability to take
the perspective of another.
However, if imitative
learning occurs in species as varied as rats, pigeons, and Japanese quail,
as it appears to, the responsible mechanism is not likely to be theory of
mind or perspective taking. But in cases in which stimulus matching
is inadequate to account for imitation, some precursor of perspective
taking is likely to be involved.
But how does a pigeon infer
the similarity between its own beak (seen only as a gross distortion) and
the beak of a demonstrator? Such an inferential process would seem to be
beyond the capacity of rats, pigeons, and quail.
(1996) has proposed that in the case of human infants, there is an
“inbuilt drive to ‘act like’ their conspecifics (p. 363). Metzoff
bases his conclusion on data suggesting that infants (and even newborns,
Metzoff & Moore, 1989; Reissland, 1988) imitate a wide range of adult
demonstrated gestures, including lip, cheek, brow, head, and finger
movements, as well as emotional expression. Although Jones (1996)
suggested that early research on infant imitation involving tongue
protrusion may be accounted for more parsimoneously in terms of very early
attempts at the oral exploration of objects, the range of imitated
gestures as well as the number of independent reports of such imitation (Metzoff,
1996) suggest that these effects cannot easily be explained away.
The implications of infant
imitation are important because if true imitation can occur in newborns,
it suggests that the mechanisms responsible for imitation are probably not
cognitively based. Clearly, even the most rudimentary cognitive structures
involved in perspective taking would not have had time to develop in
The data suggest that
infants are born with the ability to engage in “a matching-to-target
process in which they actively compare the visual information about the
seen body movements [of the adult] with the proprioceptive feedback from
their own movements in space” Metzoff (1996, p. 351). Such innate
cross-modal matching must be quite different from Piaget’s
experienced-based process. Metzoff’s data suggest that infants do not
have to learn the correspondence between the behavior of others and their
own, they just appear to do so reflexively. According to this view,
infants are “prewired” to imitate the behavior of conspecifics. But
the mechanism cannot be so general. Generalized imitation is a category of
matching behavior that is defined by the third party (e.g., the
experimenter). To the imitator, there is no match, especially if learning
is not involved. Thus if imitation (in humans at least) is an innate
response, then each demonstrated behavior that is imitated (e.g., tongue
protrusion and brow movement) must be a releaser for the same behavior in
the infant. Given the wide range of imitated behavior, the list of
releasers must be quite long.
It is difficult to imagine
the evolution of such an elaborate set of releasers to account for
imitation by humans, however, in species for which a more cognitive
perspective-taking account seems even less probable (e.g., quail and
pigeons) the existence of such a set of predisposed releasers definitely
may be involved.
Procedures have now been developed which are capable of separating
true imitative learning from other social influences on behavior. Early
results indicate that imitative learning can be found in a variety of
species. Such findings should not be surprising because social learning,
by imitation and otherwise, provides clear benefits to many organisms
over genetically based behavior and trial-and-error learning. The
mechanism by which animals are able to match their behavior to that of a
demonstrator may involve some form of coordination of visual and tactile
sensory modalities, and in some species, such coordination may be
predisposed. However, a more complete account of these processes will
have to await research to determine the necessary and sufficient
conditions for obtaining the various forms of imitative learning in
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Preparation of this article was supported by Grant MH
55118 from the National Institute of Mental Health and by Grant IBN
9414589 from the National Science Foundation.