Prelocomotor infants spend most of their waking moments simply observing their surround. Research using a sensory preconditioning (SPC) paradigm has revealed that infants form associations between events they see together. Currently, we examined whether older infants form associations in the same way.
In SPC, an association is formed when two stimuli co-occur (preexposure: A-B); association formation is confirmed when a response conditioned to stimulus A transfers to stimulus B. In prior research, 3- and 6-month-olds associated two puppets that were presented simultaneously. Research with rat pups found that formation of an A-B association is differentially affected during development by the timing regimen during A-B preexposure. Newborns associated two odors only when they were presented simultaneously; 12-day-olds associated the odors whether they were presented simultaneously or sequentially; 21-day-olds associated the odors only when they were presented sequentially.
The present study used a deferred imitation task to examine whether older human infants form an A-B association and, if so, whether the timing of the preexposure regimen also shifts developmentally. Six-, 9-, and 12-month-olds received simultaneous or sequential preexposure to puppets A and B (Days 1-2). Puppets were displayed simultaneously or sequentially, after interstimulus intervals (ISIs) of 0, 7.5, 15, 30, or 60 s. We then modeled three target actions on puppet A (Day 3) and tested whether infants imitated them on puppet B (Day 4). Puppets were associated only when presented simultaneously at 6 months of age, when presented either simultaneously or sequentially (0-s ISI) at 9 months, and only when presented sequentially (7.5- and 30-s ISI) at 12 months. This developmental pattern parallels prior findings with rat pups and most likely reflects a shift from contiguous ("what goes with what") to anticipatory ("what comes after what") stimulus relationships. Nine-month-olds associated puppets after a longer ISI (15 s) with more presentations, revealing that experiential factors also affect association formation. At all ages, association formation was unrelated to infants' looking times, motor skills, or verbal skills. In sum, infants associate two objects that they merely see together, but the effective preexposure regimen shifts from simultaneous to sequential during the first postnatal year.Ph.D.Includes bibliographical references (p. 55-61)by Kimberly Cueva
