Discrimination of single features and conjunctions by children.
Stimuli that are discriminated by a conjunction of features can show more rapid early processing in adults. To determine how this facilitation effect develops, the processing of visual features and their conjunction was examined in 7-12-year-old children. The children completed a series of tasks in which they made a target-non-target judgement as a function of shape only, colour only or shape and colour features, while event-related potentials were recorded. To assess early stages of feature processing the posteriorly distributed P1 and N1 were analysed. Attentional effects were seen for both components. P1 had a shorter latency and P1 and N1 had larger amplitudes to targets than non-targets. Task effects were driven by the conjunction task. P1 amplitude was largest, while N1 amplitude was smallest for the conjunction targets. In contrast to larger left-sided N1 in adults, N1 had a symmetrical distribution in the children. N1 latency was shortest for the conjunction targets in the 9-10-year olds and 11-12-year olds, demonstrating facilitation in children, but which continued to develop over the pre-teen years. These data underline the sensitivity of early stages of processing to both top-down modulations and the parallel binding of non-spatial features in young children. Furthermore, facilitation effects, increased speed of processing when features need to be conjoined, mature in mid-childhood, arguing against a hierarchical model of visual processing, and supporting a rapid, integrated facilitative model.
Taylor
M J
MJ
CerCo-CNRS UMR 5549, Faculté de Médecine de Ranguiel, Université Paul Sabatier, 133, route de Narbonne, Toulouse 31062, France. margot.taylor@cerco.ups-tlse.fr
Chevalier
H
H
Lobaugh
N J
NJ
D000375:Aging / Q000523:psychology; D001288:Attention / Q000502:physiology; D002648:Child; D004192:Discrimination, Psychological / Q000502:physiology*; D004566:Electrodes; D004569:Electroencephalography; D005260:Female; D005556:Form Perception / Q000502:physiology; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D014796:Visual Perception / Q000502:physiology*