Effects of ecologically relevant manipulations on infant discrimination learning

Abstract

In our laboratory, persistent attempts to establish an operant discrimination in 4-month-old infants met with limited success, even though the procedures involved readily conditionable head-movement responses, highly discriminable audiovisual stimuli, and potent sensory reinforcers. On the assumption that discriminative learning might be facilitated by experimental arrangements which were less arbitrary and better aligned with the infant's natural endowment, modifications designed to take advantage of the young baby's presumed sensitivity to the locus of incoming stimulation were introduced. Thus, (1) a more naturalistic response-consequence relationship was achieved by placing reinforcement at the end of the heat-rotation are rather than at midline and by emphasizing the orientational rather than the manipulative character of the response, and (2) the discriminanda were presented in separate locations in the vertical plane rather than in a single midline position. As a consequence of these topographical manipulations, rapid and accurate discrimination learning was obtained. Almost all subjects ( N = 32) exhibited significant levels of correct responding on random test trials, with half the sample scoring at least 80% correct in the second of two discrimination sessions. Moreover, many infants exhibited long runs of consecutively correct responses. It remains to be determined whether the results are a function of change in the form of the response, the enhanced salience of the stimuli, or the natural predisposition of infants to associate spatially differentiated cues with spatially differentiated responses. Since, under the rearranged conditions, many infants displayed behaviors characteristic of problem-solving, it is suggested that a properly constructed discrimination learning task may be useful in examining the emergence of higher-order cognitive functions.