ORIGINAL PAPER Visual Search Targeting Either Local or Global Perceptual Processes Differs as a Function of Autistic-Like Traits in the Typically Developing Population Renita A. Almeida • J. Edwin Dickinson • Murray T. Maybery • Johanna C. Badcock • David R. Badcock Published online: 9 October 2012 Ó Springer Science+Business Media New York 2012 Abstract Relative to low scorers, high scorers on the Autism-Spectrum Quotient (AQ) show enhanced perfor- mance on the Embedded Figures Test and the Radial Fre- quency search task (RFST), which has been attributed to both enhanced local processing and differences in combining global percepts. We investigate the role of local and global processing further using the RFST in four experiments. High AQ adults maintained a consistent advantage in search speed across diverse target-distracter stimulus conditions. This advantage may reflect enhanced local processing of curva- ture in early stages of the form vision pathway and superior global detection of shape primitives. However, more prob- able is the presence of a superior search process that enables a consistent search advantage at both levels of processing. Keywords Autism-Spectrum Quotient  Visual search  Embedded Figures Test  Radial frequency patterns  Visual processing Introduction Superior search ability in individuals with autism or high levels of autistic-like traits has been extensively researched (Almeida et al. 2010a; Jarrold et al. 2005; Jolliffe and Baron-Cohen 1997; O’Riordan 2004; O’Riordan et al. 2001; Plaisted et al. 1998b; Shah and Frith 1983; Simmons et al. 2009). One visual search task that has been particu- larly effective in demonstrating this enhanced performance is the Embedded Figures Test (EFT; Witkin et al. 1971), which requires searching for and detecting a simple shape ‘embedded’ within a more complex structure. The EFT was constructed atheoretically by camouflaging a simple shape through the introduction of various factors, such as overlap, segmentation and colour variation. Therefore our previous studies (Almeida et al. 2010a, b) sought to systematically deconstruct the EFT to determine which properties are critical in enabling superior performance by those with high levels of autistic-like characteristics. Almeida et al. (2010a) created a new visual search task using radial frequency (RF) patterns as elements. These are closed contours produced by sinusoidal modulation of the radius as a function of polar angle (Wilkinson et al. 1998) and the RF of a pattern refers to the number of cycles of deformation (see Fig. 1 for example patterns). RF patterns are mathematically well-defined shapes and can be manipulated in a controlled manner (Loffler et al. 2003). Further, they can be linked to specific neural mechanisms, with local curvature being first extracted in early cortical areas V1 and V2 (Poirier and Wilson 2006) and the global shape then determined in area V4 (Gallant et al. 1996; Pasupathy and Connor 2002; Wilkinson et al. 2000) using a process that detects the polar angle between points of maximum curvature (Bell et al. 2008). Almeida et al.’s (2010a) first study examined whether enhanced ability to de-clutter (or ignore overlap) was the basis for superior search ability in individuals with high levels of autistic traits, as measured with the Autism-Spectrum Quotient (AQ; Baron-Cohen et al. 2001). The reaction time (RT) for detecting a target (RF3) was measured as a function of the number of distracter (RF4) elements in the display. The R. A. Almeida (&)  J. E. Dickinson  M. T. Maybery  J. C. Badcock  D. R. Badcock School of Psychology (M304), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia e-mail: renita.almeida1@gmail.com J. C. Badcock Centre for Clinical Research in Neuropsychiatry, Graylands Hospital, Mount Claremont, WA, Australia 123 J Autism Dev Disord (2013) 43:1272–1286 DOI 10.1007/s10803-012-1669-7