DEVELOPMENTAL DIFFERENCES IN REPEATED VISUAL SEARCH AS MODULATED BY SIGNAL TO NOISE RATIO by YINGYING YANG EDWARD C. MERRILL, COMMITTEE CHAIR

This dissertation studied developmental differences in the way simultaneous and sequential signal to noise ratios impact contextual cueing effects. Contextual cueing refers to a form of implicit associative learning of the target location and its context. Over repeated exposures, participants typically respond faster to repeated displays than to new displays that are not repeated. Previous studies have suggested that children and adults are differentially sensitive to noise (irrelevant distracters) in the displays. The current study incorporated two forms of signal to noise ratio (S/N): simultaneous S/N, defined as the ratio of predictive and unpredictive distracters within each display; and sequential S/N, defined as the ratio of repeated and new displays within each block. Three age groups participated in the study: 6-8 year old children, 10-12 year old children and college students. The results suggested that all three groups demonstrated significant and comparable contextual cueing effects across three S/N ratio conditions in the simultaneous condition. The analysis of search efficiency also suggested that all three groups demonstrated guided search. Therefore, no developmental difference was found in the simultaneous condition. The results in the sequential condition suggested that adults demonstrated significant contextual cueing effects across all three ratio conditions. Older children demonstrated significant contextual cueing effects in the high and medium conditions but only marginally significant learning in the low condition. By contrast, younger children only demonstrated significant learning in the high and medium conditions, but not in the low condition. Hence, there was a significant developmental difference in the sequential condition. iii Explicit memory tests suggested no conscious awareness about the repetition for any age group in any condition. The results suggested that adults have an intact ability to extract repeated information from the information stream, as long as it is at least 33% predictive. Contextual cueing is hence a relatively robust form of implicit learning. Children's intact learning in the simultaneous condition might have reflected their relatively mature selective attention mechanisms. Children's impairment in the sequential condition might be due to their immature working memory. The practical and methodological implications of this dissertation were also discussed. iv DEDICATION This dissertation is dedicated to my late maternal grandfather, for his love and inspiration. v LIST OF ABBREVIATIONS AND SYMBOLS a Cronbach's index of internal consistency df Degrees of freedom: number of values free to vary after certain restrictions have been placed on the data F Fisher's F ratio: A ration of …