Determinants of imitation of hand-to-body gestures in 2- and 3-year-old children

Abstract

Twenty children, ten 2-year-olds and ten 3-year-olds, participated in an AB procedure. In the baseline phase, each child was trained the same four matching relations to criterion under intermittent reinforcement. During the subsequent imitation test, the experimenter modeled a total of 20 target gestures (six trials each) interspersed with intermittently reinforced baseline trials. In each session, target gestures were selected in a pre-randomized sequence from: Set 1--ear touches; Set 2--shoulder touches; Set 3--midarm touches; and Set 4--wrist touches; subjects' responses to targets were not reinforced. In each target set, half the gestures featured in nursery matching games and were termed common targets whereas the remainder, which were topographically similar but did not feature in the games, served as uncommon targets. The children produced significantly more matching responses to common target models than to uncommon ones. Common responses were also produced as mismatches to uncommon target models more often than vice versa. Response accuracy did not improve over trials, suggesting that "parity" did not serve as a conditioned reinforcer. All children showed a strong bias for "mirroring"--responding in the same hemispace as the modeler. The 2-year-olds produced more matching errors than the 3-year-olds and most children showed a bias for responding with their right hands. The strong effects of training environment (nursery matching games) are consistent with a Skinnerian account, but not a cognitive goal theory account, of imitation in young children.

Fig 1

Four baseline gestures (B1-B4) that featured in the subjects' trained baseline matching relations, and the 20 target gestures (T1-T20) employed in the imitation test.

Fig 2a

For each 2-year-old child, percentage of target trials on which correct and mirror responses were emitted to each of 20 target gestures (T1-T20).

Fig 2b

As in Fig. 2a, for each 3-year-old child.

Fig 3

Percentages of trials on which correct and mirror responses were produced by the 2-year-olds (2Y) and the 3-year-olds (3Y) to unimanual Set 1 (T1-T4) and Set 2 (T7-T10) target gestures, and Set 3 (T13-T16) and Set 4 (T17-T20) target gestures.

Fig 4

The frequencies of children's responses to modeling of Set 1 ear touches (top panel) and Set 2 shoulder touches (bottom panel), for the two age groups. The cells with counts of target matches are shaded grey: Correct and mirror responses are presented in bold numerals; all other counts represent entirely incorrect responses. Common target gestures were T1, T3, and T5 in Set 1, and T7, T9, and T11 in Set 2; the remaining targets were designated as uncommon.

Fig 5

Percentages of trials on which children in each age group produced target matches and target mismatches. For Set 1 and Set 2 gestures, target matches (upper left panel) are plotted for unimanual ipsilateral (common) targets, unimanual contralateral (uncommon) targets, bimanual ipsilateral (common) targets, and bimanual contralateral (uncommon) targets; upper right panel shows frequencies of ipsilateral (common) gestures, contralateral (uncommon) gestures, and all other responses, emitted as mismatches across all Set 1 and Set 2 trials. For Set 3 and Set 4 gestures, target matches (bottom left panel) are plotted for top-of-arm common targets, top-of-arm uncommon targets, underside-of-arm common targets, and underside-of-arm uncommon targets; target mismatches (bottom right panel) are plotted for common gestures, uncommon gestures, and all other responses.

Fig 6

The frequencies of children's responses to modeling of Set 3 middle-arm touches (top half of table) and Set 4 lower-arm touches (bottom half of table), for the two age groups. The cells with counts of target matches are shaded grey: Correct and mirror responses are presented in bold numerals; all other counts represent entirely incorrect responses. Common target gestures were T14 and T16 from Set 3, and T19 and T20 from Set 4; all other targets were designated as uncommon.