Do infants show generalized imitation of gestures?

Abstract

Two experiments were conducted to investigate generalized imitation of manual gestures in 1- to 2-year-old infants. In Experiment 1, 6 infants were first trained four baseline matching relations (e.g., when instructed "Do this", to raise their arms after they saw the experimenter do so). Next, four novel gestures that the infants did not match in probe trials were selected as target behaviors during generalized imitation Test 1; models of these gestures were presented on unreinforced matching trials interspersed with intermittently reinforced baseline matching trials. None of the infants matched the target behaviors. To ensure that these behaviors were in the infants' motor skills repertoires, the infants were next trained to produce them, at least once, under stimulus control that did not include an antecedent model of the target behavior. In repeat generalized imitation trials (Test 2), the infants again failed to match the target behaviors. Five infants (3 from Experiment 1) participated in Experiment 2, which was identical to Experiment 1 except that, following generalized imitation Test 1, the motor-skills training was implemented to a higher criterion (21 responses per target behavior), and in a multiple-baseline, across-target-behaviors procedure. In the final generalized imitation test, 1 infant matched one, and another infant matched two target behaviors; the remaining 17 target behaviors still were not matched. The results did not provide convincing evidence of generalized imitation, even though baseline matching was well maintained and the target behaviors were in the infants' motor skills repertoires, raising the question of what are the conditions that reliably give rise to generalized imitation.

Fig 1. Range of baseline gestures (B1–B11) that featured in the subjects' trained baseline matching relations, and of target gestures (T1–T7) in the target matching relations.

Fig 2. Subjects' matching performances on the eight baseline trials (open circles), and the eight target trials (filled circles), during each session of probing for target behaviors (first two sessions), generalized imitation Test 1, and generalized imitation Test 2.

Skills training for the target behaviors, which was administered between the two tests, is shown as gray-shaded columns.

Fig 3. Matrices showing, for Rhys, Dan, and Lora, the frequency of each target response to each modeled gesture, during generalized imitation Test 2 trials.

Matching responses are shown in boxes that lie on the diagonal from top left to bottom right (shaded gray); other responses are mismatches.

Fig 4. Matching performances of Emma, Jack, and Mia in the eight baseline (open circles) trials, and the two trials per target gesture (filled circles), during each session of the multiple baseline procedure.

Following generalized imitation Test 1, number of sessions of skills-training without modeling (shaded gray columns), conducted in a stepwise manner across the four target behaviors, are shown; a generalized imitation test followed each skills training phase. Also shown for Mia are her exact matches (open triangles) to the palms up (T4) gesture.

Fig 5. For each subject, the frequency of each target response to each modeled gesture during generalized imitation test trials.

Matching responses are shown in boxes that lie on the diagonal from top left to bottom right (shaded gray); other responses are mismatches.