Categorical vs Coordinate Relationships do not reduce to spatial frequency differences


Categorical and coordinate stimulus processing were hypothesized by Kosslyn (1987) to be lateralized visual tasks, differentiated by task-relevant spatial frequencies. Slotnick et al.\ (2001) directly tested Kosslyn's hypothesis and concluded that the lateralization presents only when tasks are sufficiently difficult. Our differential encoding model is a three layer neural network that accounts for lateralization in visual processing via the biologically plausible mechanism of differences in connection spread of long-range lateral neural connections (Hsiao, Cipollini, \& Cottrell, 2013). We show that our model accounts for Slotnick's data and that Slotnick's analysis does not convincingly explain their results. Instead, we propose that Kosslyn's initial hypothesis was based on an incorrect assumption: categorical and coordinate stimuli are not solely differentiated by spatial frequencies. The results that our model captures cannot be reproduced by Ivry and Robertson's (1998) “Double Filtering by Frequency” theory, which is driven solely by lateralized spatial frequency processing.

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