| Summary: | This thesis has investigated the apparent ability of the visual system to represent a set of similar objects with a summary description instead of information about the individual items themselves (Ariely, 2001; Chong and Treisman, 2005a). Summary descriptions can be based on set sizes that are beyond the capacity of focussed attention, leading to the proposal that a distributed attention mechanism, statistical processing, underlies this process (Chong and Treisman, 2003, 2005a, 2005b; Chong et al. 2008; Treisman, 2006). However, the conclusion that summary descriptions are formed by a mechanism involving distributed attention has been questioned on the basis of parsimony, and a proposal for the role of focussed attention strategies in producing these summary descriptions has been made (Myzcek & Simons, 2008; Simons & Myzcek, 2008; see also De Fockert & Marchant, 2008). The aim of this thesis was to further elucidate the process of set representation by statistical properties, exploring the evidence that the summary description is given preferential representational status over individual items (Chapter 2), that summary descriptions can be produced within the known capacity limits of focussed attention (Chapter 3), that the results found in these experiments are not affected by the development of a prototypical average across the experimental session (Chapter 4), and that similar summary descriptions may also be rapidly extracted from more complex stimuli (Chapter 5). These findings are discussed in the context of current average size perception theory, and the proposal of a dual process view of set representation by statistical properties is briefly outlined. The dual process view combines both focussed attention when stimulus complexity is low and/or cognitive resources are available and distributed attention when stimulus complexity is high and/or cognitive resources are restricted. Finally, a selection of further studies and research areas that follow from the current research and the dual process view are briefly detailed.
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