An experimental demonstration of discriminated (nongeneralized) imitation

In a number of experiments, nonreinforced imitation has been found to persist at high rates despite the variety of procedures which have been employed to eliminate such responses. In the present experiment, powerful stimulus control was established over imitation by providing an alternative response which was reinforcible. Four children participated in a multiple-schedule experiment in which imitation was reinforced in the presence of one light and bar pressing in the presence of a second light; throughout the experiment, responses were modeled on each trial: hand-arm responses in the presence of the red light and leg responses in the presence of the yellow light. Initially, imitation was reinforced in the presence of the red light and button pressing in the presence of the yellow light. In a within-subjects design, stimulus control was demonstrated by reversing the association of lights and contingencies, then reinstating the original contingencies. The children imitated when reinforced for imitation and pressed the button when button pressing was reinforced. The results demonstrate stimulus control over imitation which is more powerful than in previous investigations and indicate that the prevailing reinforcement contingencies determine whether or not a child will imitate on a particular occasion.This research was supported by a Faculty Summer Research Grant from The American University. The authors wish to express their appreciation to the School for Contemporary Education, McLean, Virginia, and to Dr. Sally Sibley, Mr. David Williams, and Mrs. Linda Trout for their cooperation in providing subjects and research space.     

Factors effecting nonreinforced imitation: the model as a source of information or social control

Three experiments were conducted with kindergarten, second-grade, and fourth-grade children (N = 208) which investigated whether modelling of unreinforced behavior exerts control over childrens' behavior by providing information concerning other types of behavior more likely to be reinforced or by creating social demands for imitation. After learning that reinforcement was available, children observed an adult model emit a reinforced response or an unreinforced response and then remain to monitor the child's subsequent behavior or leave the situation. Compared to a no-model control, all children except kindergarten girls emitted more reinforced responses after observing the model being reinforced. Only second-grade children, however, showed performance changes after observing the unreinforced model. Second-grade children also only performed what they learned when the unreinforced model was not present. Conclusions were that the unreinforced behavior of the model serves not only as a source of information but also as a cue for unreinforced imitation.     

GENERALIZED IMITATION AND RESPONSE-CLASS FORMATION IN CHILDREN WITH AUTISM

An experimental analysis of imitation was conducted to examine the influence of response topography on generalization of imitation across three response types. Four children with autism were presented with both reinforced training trials and nonreinforced probe trials of models from vocal, toy-play, and pantomime response types. The probe trials were used to examine generalization within each response type. A multiple baseline design was used to analyze percentage of matching and nonmatching responses to models across response types. This study, the first to analyze imitative response classes in children with autism, showed that imitation generalized from reinforced training models to nonreinforced probe models within a response type, but it did not generalize across response types. Thus, functional response classes determined by topographical boundaries were exhibited within generalized imitation.     

Development of syntax in a retarded girl using procedures of imitation, reinforcement, and modelling

Three experiments demonstrated the development and generalized use of a singular and plural declarative sentence in a child initially lacking sentence form responses. In each experiment, an adult(s) served as a language model(s), and consequences (sweets) were provided for imitation of the model. During training trials, an item(s) was displayed first to the model(s) then to the subject; these displays were accompanied by requests to label the item(s). Generalization was assessed by a number of probe trials that were periodically interspersed among training trials. During these trials, the subject was requested to label the displayed item(s) without any preceding labelling response from the model. Using these procedures, generalized use of a singular sentence ("That is one-") resulted in Experiment I, and generalized use of a plural sentence ("These are two-") resulted in Experiment II. In Experiment III, two models (a singular and a plural sentence model) were made available to the subject but imitation of only one model was reinforced during any one condition. Results indicated the subject labelled probe (generalization) items with the same sentence form that was modelled and reinforced during training trials.     

Effects of vicarious consequences on imitation and recall: Some developmental findings

Two experiments were conducted using a multiple-item list in which each item consisted of a pair of pictures. The model indicated which member of each pair she preferred and was either positively reinforced, negatively reinforced, or received neutral consequences. The S then indicated his preferences (imitation test). Following the imitation test, each S was asked to recall the model's choices. Age was an independent variable in both experiments. Imitation scores of the children, preschool to sixth-grade age range, were strongly influenced by differential vicarious reinforcement. Vicarious reward increased imitation and vicarious punishment decreased it. College students' imitation scores were only minimally influenced by differential vicarious reinforcement. Within- and between-subjects variations of vicarious reinforcement had similar effects. Recall scores were surprisingly high and were not significantly influenced by differential vicarious reinforcement. Interestingly, age and percentage of correct recall were negatively correlated.     

Behavioral similarity as a reinforcer for preschool children

Three experiments evaluated whether behavioral similarity provided by an adult could serve as a reinforcer for the modelling behavior of four preschoolers. In each experiment, sessions consisted of two kinds of trials: (1) experimenter-modelled trials, when the child's imitation of modelled motor responses was reinforced with praise and tokens, and (2) child-modelled trials when experimenter imitation of child-modelled responses was contingent upon the child's modelling one of three alternative responses: operation of a ball, horn, or clicker. Experiment I showed that the children consistently modelled whichever responses the experimenter imitated. Experiment II determined whether that performance was due to differences in the amount of experimenter behavior following imitated versus nonimitated child models or to experimenter imitation. Neither reducing nor increasing the amount of experimenter behavior following the children's nonimitated models altered their modelling of imitated responses. Experiment III evaluated whether experimenter imitation of child models was a reinforcer because the child's imitative responses were reinforced on experimenter-modelled trials. In Experiment III, the children's nonimitation of experimenter-models was reinforced with praise and tokens on a schedule of differential reinforcement of other behavior, yet they continued to model experimenter-imitated responses on child-modelled trials. These results indicate behavioral similarity was reinforcing, though no conditioning history through which it acquired that function was demonstrated.     

The social control of generalized imitation

Instructions, discrimination procedures, and sources of reinforcement were manipulated in order to determine the bases for the maintained "non-reinforced" imitations observed in generalized imitation research. Six girls received imitation training from two experimenters. One experimenter modelled only reinforced responses; the other modelled only non-reinforced responses. The children imitated all responses when no reinforced alternative was available, even though results of choice procedures and special instructions clearly demonstrated that they discriminated reinforced from non-reinforced responses. Instructions not to perform non-reinforced imitations immediately eliminated these behaviors. It is suggested that social setting events may be largely responsible for generalized imitation.     

DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES? II. THE EFFECTS OF SKILLS TRAINING AND MULTIPLE EXEMPLAR MATCHING TRAINING

The determinants of generalized imitation of manual gestures were investigated in 1‐ to 2‐year‐old infants. Eleven infants were first trained eight baseline matching relations; then, four novel gestures that the infants did not match in probe trials were selected as target behaviors. Next, in a generalized imitation test in which matching responses to baseline models were intermittently reinforced, but matching responses to target models were not eligible for reinforcement, the infants matched baseline models but not the majority of their target behaviors. To ensure their failure to match the target behaviors was not due to motor constraints, the infants were trained, in a multiple‐baseline procedure, to produce the target responses under stimulus control that did not include an antecedent model of the target behavior. There was no evidence of generalized imitation in subsequent tests. When the infants were next trained to match each target behavior to criterion (tested in extinction) in a multiple‐baseline‐across‐behaviors procedure, only 2 infants continued to match all their targets in subsequent tests; the remaining infants matched only some of them. Seven infants were next given mixed matching training with the target behaviors to criterion (tested in extinction); they subsequently matched these targets without reinforcement when interspersed with trials on which matching responses to baseline models were intermittently reinforced. In repeat tests, administered at 3‐week intervals, these 7 children (and 2 that did not take part in mixed matching training) continued to match most of their target behaviors. The results support a trained matching account, but provide no evidence of generalized imitation, in 1‐ to 2‐year‐old infants.     

Effects of verbal imitation and comprehension training on verbal production

This study sought to determine whether some combination of imitation training and comprehension training was necessary to achieve verbal production or whether comprehension training alone was sufficient to result in verbal production. Fifty-one first- and second-grade subjects were trained to imitate eight words (Spanish nouns) for which there were no referents. An additional set of eight words was trained in a comprehension task where overt verbal rehearsal was prohibited. Once criterion of two successive sessions of 100% performance was reached in training for both imitation and comprehension, training modes were reversed so that items initially trained in imitation were then trained in comprehension andvice versa. Results showed that initial comprehension training did result in some verbal production, whereas initial imitation training, as expected, did not. A marked improvement in verbal production performance was observed when initial comprehension training was followed by imitation training. When initial imitation training was followed by comprehension training, verbal production also resulted but not to the degree or with the consistency of performance which marked the comprehension-then-imitation sequence. Furthermore, comprehension training required more trials to reach a similar level of proficiency when it followed imitation training than when it preceded imitation. These data indicate that initial imitation training interferes with acquisition of subsequent comprehension and production responses and that the preferred training sequence is one which initially focuses on comprehension and follows this with verbal imitation.This study was supported by Grant HD 00870 from the National Institute of Child Health and Human Development and Grant NS 10468 from the National Institute of Neurological Diseases and Stroke awarded to the Bureau of Child Research, University of Kansas, Lawrence, Kansas.     

Stimulus equivalence and arbitrarily applicable relational responding.

Subjects' responses to nonarbitrary stimulus relations of sameness, oppositeness, or difference were brought under contextual control. In the presence of the SAME context, selecting the same comparison as the sample was reinforced. In the presence of the OPPOSITE context, selecting a comparison as far from the sample as possible on the physical dimension defined by the set of comparisons was reinforced. Given the DIFFERENT context, selecting any comparison other than the sample was reinforced. Subjects were then exposed to arbitrary matching-to-sample training in the presence of these same contextual cues. Some subjects received training using the SAME and OPPOSITE contexts, others received SAME and DIFFERENT, and others received SAME, OPPOSITE, and DIFFERENT. The stimulus networks established allowed testing for a wide variety of derived relations. In two experiments it was shown that derived performances were consistent with relational responding brought to bear by the contextual cues. In contexts relevant to the relation of sameness, stimulus equivalence emerged. Other kinds of relational networks emerged in the other contexts. Arbitrarily applicable relational responding may give rise to a very wide variety of derived stimulus relations. The kinds of performances seen in stimulus equivalence do not appear to be unique.     

The development of imitation by reinforcing behavioral similarity to a model

This research demonstrated some of the conditions under which retarded children can be taught to imitate the actions of adults. Before the experiment, the subjects were without spontaneous imitative behavior, either vocal or motor. Each subject was taught, with food as reinforcement, a series of responses identical to responses demonstrated by an experimenter; i.e., each response was reinforced only if it was identical to a prior demonstration by an experimenter. Initially, intensive shaping was required to establish matching responses by the subjects. In the course of acquiring a variety of such responses, the subjects' probability of immediate imitation of each new demonstration, before direct training, greatly increased. Later in the study, certain new imitations, even though perfect, were never reinforced; yet as long as some imitative responses were reinforced, all remained at high strength. This imitativeness was then used to establish initial verbal repertoires in two subjects.     

Behavioral treatment of children with phonological disorder: the efficacy of vocal imitation and sufficient-response-exemplar training

This study examined whether sufficient-response-exemplar training of vocal imitation would result in improved articulation in children with phonological disorder, and whether improved articulation established in the context of vocal imitation would transfer to other verbal classes such as object naming and conversational speech. Participant 1 was 6 years old and attended first grade in a regular public school. Participant 2 was 5 years 4 months old and attended a public kindergarten. Both participants had normal hearing and no additional handicaps. A multiple baseline design across behaviors (target sounds or blends) was employed to examine whether the vocal imitation training resulted in improved articulation. Results showed that both participants improved articulation once training was implemented, and that the improved articulation transferred from vocal imitation to more natural speech such as object naming and conversational speech. Improvement established during training was maintained posttraining and at a 6-month follow-up.     

The effects of a discriminative cue and an incompatible activity on generalized imitation

Four noncompliant retardates were observed in a generalized imitation study. Two variables were studied: provision of a competing reinforced activity, and use of a cue to aid discrimination between reinforced and nonreinforced imitations. Both variables were found to increase the rate of discrimination between the two sets of stimuli. Greatest discrimination occurred when both cue and alternative task were present. Discrimination decreased when the variables were removed. Results are interpreted as implying that imitation of nonreinforced cues in generalized imitation procedures varies with the degree to which reinforcement is available for other activity, as well as with the complexity of the discrimination problem. These results help indicate conditions under which the generalized imitation effect may be observed in more naturalistic settings.     

Training generative verb usage by imitation and reinforcement procedures

Three retarded children were trained, using imitation and reinforcement procedures, to produce past and present tense forms of verbs in response to verbal requests. Two types of experimental sessions were arranged: training sessions and probe sessions. During training sessions, a child was trained to produce one verb in both the past and the present tense. Then, in a probe session, the generalization of this training was tested by presenting to the child a series of untrained verbs interspersed with previously trained verbs. Responses to untrained verbs were never reinforced. Training sessions alternated with probe sessions throughout a multiple baseline design involving four classes of verb inflections as the baselines. The results showed that, as past and present tense forms of verbs within an inflectional class were trained, the children correctly produced past and present tense forms of untrained verbs within this class. When verbs from two or more classes were trained, the children correctly produced the verb tenses from each of these classes. Thus, the imitation and reinforcement procedures were effective in teaching generative use of verb inflections.     

An experimental analysis of linguistic development: the productive use of the plural morpheme

Operant conditioning procedures were used to establish a generative use of the plural morpheme in the speech of a severely retarded girl. During training trials, reinforcement was presented contingent upon correct imitation of singular and plural verbalizations by the experimenter, in response to objects presented to the subject singly and in pairs. A generative productive plural usage resulted, the girl correctly labeling new objects in the singular or plural without further direct training relevant to those objects. After establishing the singular/plural usage, the contingencies were reversed (reinforcement of plural responses to single objects, and vice-versa). This produced a corresponding reversal of response by the child. The original usage was then recovered by returning to the previous contingencies. A second experiment analyzed certain error responses occurring during the first experiment, and further probed the generative nature of the subject's plural usage. It was found that errors were somewhat more likely to occur in the pluralization of words ending in vowels than of words ending in consonants. Furthermore, several words whose plurals had been learned according to the reversed plural rule, when examined later during reinforcement of normal plural usage, were found then to exemplify the normal rule being reinforced, yet without direct training.     

Establishing discriminative stimulus control within generalized oddity performance,without reinforcement

In two oddity learning studies with children, subjects were reinforced for oddity (or nonoddity) responding on line-tilt or dot numerosity problems. Interposed form and color problems were not reinforced. No instructions to make oddity choices were given. In Experiment I it was found that reinforcement for oddity or nonoddity responding on tilt and numerosity problems produced the corresponding tendency toward oddity or nonoddity performance on these problems and also on the nonreinforced form and color problems. These results show a generalized oddity phenomenon similar to generalized imitation. In Experiment II a third type of nonreinforced problem was presented in this same format: compound stimuli permitting either a color or a form solution. It was found that immediate prior training with nonreinforced form problems, interpolated among the reinforced tilt and numerosity problems, led to form-oddity choices in the compound problems. Similarily, color pretraining produced color-oddity choices. These results show that selective discriminative stimulus control can be obtained in oddity learning, without reinforcement for choices on either of the two dimensions involved.     

The impact of body-part-naming training on the accuracy of imitative performances in 2- to 3-year-old children

A series of three experiments explored the relationship between 3-year-old children's ability to name target body parts and their untrained matching of target hand-to-body touches. Nine participants, 3 per experiment, were presented with repeated generalized imitation tests in a multiple-baseline procedure, interspersed with step-by-step training that enabled them to (i) tact the target locations on their own and the experimenter's bodies or (ii) respond accurately as listeners to the experimenter's tacts of the target locations. Prompts for on-task naming of target body parts were also provided later in the procedure. In Experiment 1, only tact training followed by listener probes were conducted; in Experiment 2, tacting was trained first and listener behavior second, whereas in Experiment 3 listener training preceded tact training. Both tact and listener training resulted in emergence of naming together with significant and large improvements in the children's matching performances; this was true for each child and across most target gestures. The present series of experiments provides evidence that naming--the most basic form of self-instructional behavior--may be one means of establishing untrained matching as measured in generalized imitation tests. This demonstration has a bearing on our interpretation of imitation reported in the behavior analytic, cognitive developmental, and comparative literature.     

An experimental analysis of verbal imitation in preschool children

A model presented English words to three preschool children and reinforced accurate imitation of these words. The model also presented novel Russian words but the subjects' imitation of these words was never reinforced. As long as the subjects' imitation of English words was reinforced, their accuracy of imitating non-reinforced Russian words increased. When reinforcement was not contingent upon imitation of English words, accuracy of imitating both the English and the Russian words decreased. These results support and extend previous work on imitation.