Effects of bottom-up versus top-down cueing on conjunction search in 3-month old infants
Fuda, Maria Christina
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Previous research with infants have suggested that they are fully capable of performing a feature search in a manner nearly identical to adults (Adler & Orprecio, 2006), but are developmentally immature in localizing a target in a conjunction search (Fuda & Adler, 2012). An explanation for the difference in infants performance between feature and conjunction searches was attributed to Wolfe's (1989) Guided Search model of visual search, in which feature searches are thought to rely mainly on bottom-up attentional resources to localize a target, whereas conjunction searches are theorized to require both bottom-up and top-down attentional resources. Because infants have been shown to perform a feature search like that of adults but have been shown not to be able to perform a conjunction search in a similar manner, the current study attempted to show that bottom up attentional mechanisms develop before top-down mechanisms. To this end, 3-month-old infants were presented with two types of cues prior to a conjunction search array that ·will provide them with prior bottom-up or top-down information that might facilitate their performance in a conjunction search task. The bottom-up cue consisted of four rectangular frames indicating where the possible location of the target will be, while the top-down cue consisted of the flashing what the target will be in the center of the array. Infant saccadic eye movement latencies were recorded for three different set sizes of conjunction search arrays (5, 8, & 10) when the target was either present or absent. When the target was present, the eye movement latency that localized the target was measured, while when the target was absent the first eye movement latency was measured. Results showed that the top-down cue, but not the bottom-up cue, facilitated the exhibition of a more adult-like conjunction search function in which latencies increased with increasing set sizes. More specifically, the bottom-up cue resulted in relatively flat search functions for both the target-present and target-absent trials. In contrast, the top-down cue results showed that in the second half of all infant trials, target-present latencies increased with increasing set sizes, while target-absent latencies decreased with increasing set sizes. These results show that infants are developmentally mature in their bottom-up processing, but immature in their top-down processing abilities, and as such the top-down cue provided the facilitation that they needed in order to localize a target in a conjunction search. The current study is the first of its kind to show that 3-month-old infants' top-down processing mechanisms are developmentally immature compared to their bottom-up mechanisms in visual search tasks.