Grouping by form in young infants: only relevant variability promotes perceptual learning.

Infants do not readily organize visual pattern information using form similarity: 3 to 4 month olds familiarized with arrays consisting of alternating columns or rows of a given element contrast do not display a subsequent preference for a novel organization of horizontal versus vertical bars. However, when array types composed of different element contrasts are presented during familiarization, infants perform successfully, indicating that variability in pattern information depicting an invariant structure promotes perceptual learning. In the current investigation, we examined whether the type of variability (relevant versus irrelevant) impacts this learning, as a way to understand the specificity and mechanism underlying the learning. In experiment 1, one group of infants (relevant variability) was familiarized with three element contrasts forming column-row arrays on different trials, and a fourth element contrast that formed an outer enclosing context on all trials. For the other group (irrelevant variability), the column-row array was composed of the same element contrast across trials, while the outer context differed across trials by being composed of three different element contrasts. Only the relevant variability group performed successfully. Experiment 2 showed that the failure of irrelevant variation to facilitate organization was not due to insensitivity to the variation among elements in the outer context. The findings suggest that variation which emphasizes global structure and deemphasizes local element information is a significant factor in facilitating perceptual learning.