THE DEVELOPMENT AND GENERALIZATION OF DELAYED IMITATION1

An individual's behavior can be identified as imitative if it temporally follows the behavior of another individual and if its topography is controlled by the demonstrated behavior [Baer, Peterson, and Sherman (Journal of the Experimental Analysis of Behavior, 1967, 10 , 405–416)]. This definition takes into account both temporal and topographical characteristics of the behavior in question. More recent research in the area of imitation has interpreted the temporal component of the above definition differentially by limiting imitation to those topographically similar responses occurring within 3, 5, or 10 sec after a model's demonstration. Yet, Gewirtz and Stingle (Psychological Review, 1968, 75 , 375–397) pointed out that much of the imitation seen in young children is not of this immediate nature, but instead occurs sometime after a model's response. They further suggest that this type of imitative behavior can be characterized as a response class and is susceptible to development and modification as a function of consequences delivered to subjects contingent on this type of delayed responding. Four retarded children, three initially imitative and one nonimitative, were individually trained to imitate a number of motor responses in an immediate and a delayed fashion. Immediate imitation was defined as a response similar to a model's demonstration occurring within 5 sec after the model's demonstration; delayed imitation was defined as a response similar to a model's demonstration occurring more than 5 sec, but not more than 25 sec, after the model's demonstration. A reversal (ABAB) design was employed to examine the experimental development of a generalized delayed imitative repertoire. Untrained probe responses were demonstrated to subjects systematically through the ongoing training. Generalized immediate and delayed imitation were observed in each subject; this generalization was restricted to the type of imitation currently undergoing training. This development of a generalized imitation repertoire was observed in each subject. That is, these subjects imitated some responses that had never been specifically trained. More importantly, a training package consisting of prompting, fading, and consequences for delayed imitation functioned to develop generalized delayed imitation. These data exemplify a special case of generalization that was a function of the most recent training history of immediate or delayed imitation. The reversal design demonstrated that imitations of nontrained models were either delayed or immediate, depending upon which form of imitation was currently receiving training. Therefore, for each form of imitation trained, delayed or immediate, a corresponding response class was demonstrated. These data relate to data reported by Garcia, Baer, and Firestone (Journal of Applied Behavior Analysis, 1971, 4 , 101–112). The association lies in the proposition that there are identifiable boundaries of generalized imitation and that these boundaries are functionally related to previous training histories.     

Changes in imitative behavior during early infancy

Changes in imitative behavior and attentiveness were observed in 40 infants when they were 2 to 6 months of age. The facial expressions happy, sad, and surprised were modeled in a trials-to-criterion procedure, and the infants' looking time and mouth movements were recorded by an observer who was unaware of the face being modeled. In addition, the observer recorded her guess as to the expression being modeled by the corresponding expression on the infant's face and rated the infant's expressivity. The results suggested that looking time, correspondence between the mouth expression of the infant and the mouth expression modeled, accuracy of the observer's guess, and expressivity ratings decreased from 2 to 3 and 4 to 6 months. Although matching of mouth movements with the modeled mouth movements and accuracy of guesses were greater than chance over the 2 to 6 month-period, the decreases in these measures suggest that imitative behavior declined across early infancy. The decrease in looking time suggests that imitative behavior and attentiveness may be related and highlights the limitation of this paradigm for assessing the development of imitation during early infancy.     

Operant and nonoperant vocal responding in the mynah: Complex schedule control and deprivation-induced responding

Several recent studies have been concerned with operant responses that are also affected by nonoperant factors, (e.g., biological constraints, innate behavior patterns, respondent processes). The major reason for studying mynah vocal responding concerned the special relation of avian vocalizations to nonoperant emotional and reflexive systems. The research strategy was to evaluate operant and nonoperant control by comparing the schedule control obtained with the vocal response to that characteristic of the motor responses of other animals. We selected single, multiple, and chain schedules that ordinarily produce disparate response rates at predictable times. In multiple schedules with one component where vocal responding (“Awk”) was reinforced with food (fixed-ratio or fixed-interval schedule) and one where the absence of vocal responding was reinforced (differential reinforcement of other behavior), response rates never exceeded 15 responses per minute, but clear schedule differences developed in response rate and pause time. Nonoperant vocal responding was evident when responding endured across 50 extinction sessions at 25% to 40% of the rate during reinforcement. The “enduring extinction responding” was largely deprivation induced, because the operant-level of naive mynahs under food deprivation was comparable in magnitude, but without deprivation the operant level was much lower. Food deprivation can induce vocal responding, but the relatively precise schedule control indicated that operant contingencies predominate when they are introduced.     

IMPROVING THE GENERALIZED MNEMONIC PERFORMANCE OF A DOWN'S SYNDROME CHILD1

A training program was conducted to improve the generalized mnemonic performance, or memory, of a Down's Syndrome child. Training was directed at digit-span performance with generalization from training determined by responses to untrained mnemonic performance probes. The digit-span items varied in length from three to five digits. Each length constituted an item class, with each class trained within the framework of a multiple-baseline design. Probes consisted of untrained digit-span items, grammatical sentences, nongrammatical sentences, and match-to-sample items. A training procedure, in which 15 items from each class varied continually from trial to trial and from day to day, resulted in the percentage of correct responses to both training and probe items increasing to levels substantially above baseline. The results demonstrate the effectiveness of the training procedure in improving the generalized mnemonic performance of a Down's Syndrome child.     

Social learning by following: an analysis

Learning by “following”, probably a common means by which behaviors are socially transmitted from adults to young in many species, was analyzed. Pigeons first learned to eat from a human hand. When the hand then approached an operant key and pecked it, the pigeons followed and quickly learned to do the same, thereby demonstrating social learning. When the hand only led the birds to the area of the key, without demonstrating the key-peck response, the birds learned as rapidly as with a key-peck demonstration. Birds also learned, but less reliably and more slowly, when they could observe the hand's responses but were constrained and unable to follow. “Following” was also shown to engender very rapid learning of a more complex, two-member response chain.     

The history of imitation in learning theory: the language acquisition process

The concept of imitation has undergone different analyses in the hands of different learning theorists throughout the history of psychology. From Thorndike's connectionism to Pavlov's classical conditioning, Hull's monistic theory, Mowrer's two-factor theory, and Skinner's operant theory, there have been several divergent accounts of the conditions that produce imitation and the conditions under which imitation itself may facilitate language acquisition. In tracing the roots of the concept of imitation in the history of learning theory, the authors conclude that generalized imitation, as defined and analyzed by operant learning theorists, is a sufficiently robust formulation of learned imitation to facilitate a behavior-analytic account of first-language acquisition.     

Neonatal imitation, gaze aversion, and mother-infant interaction

A relationship between elicited imitation in neonates and social interaction has been proposed by several investigators. The present work examines if such a relationship can be found when studying neonatal imitation, gaze aversion, and mother-infant interaction. Thirty-two infants were observed at 2 to 3 days, 3 weeks, and 3 months of age. Imitation of tongue protrusion and mouth opening was assessed in all three observations. In addition, a face-to-face interaction between mother and child was included when the child reached 3 months of age. The most striking result was a negative relationship between the infants' brief gaze aversion observed at 3 months of age while interacting with their mothers and the infants' imitative reactions at 2 to 3 days, 3 weeks, and 3 months of age. Behaviorally, these patterns indicate that high-imitating infants tend to display fewer episodes of brief gaze aversion when interacting with their mothers.