Abstract
Purpose: By manipulating lower-level sensory (e.g., spatial frequency (SF), abrupt vs. ramped onsets) and higher-level perceptual (e.g., presence or absence of 3-D objects) stimulus variables we have previously found greater location-based IOR under P/ventral biased conditions and less IOR under M/dorsal biased conditions (Guenther & Brown, VSS 2007; 2008). The presence/perception of 3-D objects increased IOR overall and interacted with stimulus SF influencing IOR in the Guenther & Brown (2007) study. The present experiments were designed to test two alternative explanations for these object effects. First, the object effects were due to the increased high SF content associated with the objects edges/contours. Second, the object effects were due to the SF targets appearing as texture on the front surface of the objects. Method: Experiment 1 tested the first alternative account using blurry objects (i.e., with their high spatial frequency components removed but retaining their appearance as objects). Experiment 2 tested the second alternative account by presenting the 3-D objects displaced from the locations of the cues and targets. Cues and targets were Gabor patches presented in the upper/lower visual fields, in blurry 3-D objects (Exp. 1) or next to 3-D objects (Exp 2), using cue-to-target timing known to produce location-based IOR. Simple RT to target onset was measured. Different SF pairings were tested (1+12cpd; 1+4cpd; 4+12cpd). Results: Location-based IOR was influenced by target SF in both experiments replicating Guenther & Brown (2007). Conclusions: The object effects observed previously can be attributed to the increased P/ventral activity associated with the presence and perception of the 3-D objects and not due to low-level sensory influences due to their edges or the perception of the targets as texture on their front surface.