Stimulus duration as an age-dependent factor in reflex blinking

Alternative hypotheses of differential development of auditory and visual systems versus temporal-processing systems were tested to explain prior adult-infant differences in reflex blink latency. The present study removed a confound between stimulus modality and duration, present in prior work, and determined whether age interacted with modality or with duration when they were varied orthogonally. Reflexes were elicited from human adults and infants under 4 stimulus conditions: flash and click, delivered singly and in trains. Age interacted only with duration to affect latency and elicitation probability, reflex characteristics which depend on adequate triggering by a transient change at onset. In contrast, age did not interact with duration to affect peak amplitude which presumably depends on temporal integration. Findings are compatible with the hypothesis that processes or structures, specialized for differentiation of transient stimulus change, mature at a different rate than those specialized for integration of stimulus energy over time.