Discrimination learning during the first year: stimulus and positional cues

In four studies, 3-. 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-montholds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues. In the past 30 years there have been major advances in our knowledge base on cognition in preverbal humans. In contradiction to James' (1892) characterization of the infant's world as a "blooming, buzzing confusion," demonstrations of relatively sophisticated sensory, perceptual, and cognitive capacities (e.g., Yonas, 1988) have given rise to the conceptualization of the human infant as an active processor of input. For example, by capitalizing on infants' tendencies to visually habituate to repeated stimulus presentations (e.g., Cohen, 1976) and/or to fixate novel stimuli over familiar (e.g., Fagan, 1971), the operation of such basic information-processing components such as stimulus encoding, comparison, and discrimination have been documented. In spite of such advances, the inquiry into early information processing has not dealt with higher order processes of learning and acquisition that are commonly addressed in information-processing studies with older children and adults. Such questions include how attention and encoding processes