Habituation of the orienting response to stimuli of different functional values in 4-month old infants.

In experiments on infant attention, the sudden presentation of a stimulus elicits an orienting response (OR). Its persisting presence then reinforces its visual exploration. When subsequently projected, this stimulus comes to signal the availability of something to look at. The aim of the present study was to sort out the effect of these three functional values of stimuli on OR elicitation. Fifty 4-month-old infants (M = 120 days) were randomly assigned to one of three experimental conditions. In Condition 1, they received 12 presentations of a 2-s visual stimulus. In Condition 2, the same 12 short stimuli presentations were accompanied by the projection of another event, visible after having the infant's gaze oriented toward the first stimulus. Condition 3 was a infant-control procedure: the same stimulus was repeatedly presented and remained on for as long as the infant looked at it. In each condition, half of the infants were shown a 4 x 4 checkerboard pattern, the others a 8 x 8 pattern. After this phase of repetitive presentation of one checkerboard pattern, the other was presented for two test trials, followed by two dishabituation trials with the initial first pattern. When the eliciting function of the stimulus (Condition 1) was isolated, orienting responses decreased over trials, and were of different latencies, according to stimulus complexity. On the other hand, the isolated function of the stimulus (Condition 2) raised its capacity to elicit ORs. Stimulus complexity was a determining factor in OR habituation, in attention recovery and in dishabituation for Conditions 1 and 3, but it was overshadowed by its signaling function in Condition 2. These results suggest the importance of taking into account the functional value of stimuli when analyzing infant attention.