Ks. Kraebel et Ne. Spear, Infant rats are more likely than adolescents to orient differentially to amodal (intensity-based) features of single-element and compound stimuli, DEVELOP PSY, 36(1), 2000, pp. 49-66
An infantile predisposition to process quantity, over quality, of stimulati
on has been suggested in theories of cognitive and perceptual development,
as well as for understanding ontogenetic differences in learning. In the pr
esent study, responsivity to stimulus intensity was assessed in preweanling
and periadolescent rats by using magnitude of cardiac orienting as an inde
x of perceived stimulus intensity. In experiment 1, cardiac orienting was m
easured to low- and high-intensity auditory and visual stimuli in 15-, 17-,
and 30-day-old rats. The results demonstrated that younger rats are more p
redisposed to respond differentially to single-element stimuli on the basis
of stimulus intensity. Experiments 2, 3, and 4 examined cardiac orienting
in preweanlings to compound stimuli. In accordance with studies of ontogeny
of learning, the results of these experiments indicated that preweanlings
process compound stimuli on the basis of net intensity, but only if there h
ad been no prior experience with the compound's elements. (C) 2000 John Wil
ey & Sons, Inc.