Attention changes perceived size of moving visual patterns

Abstract

Spatial attention shifts receptive fields in monkey extrastriate visual cortex toward the focus of attention (S. Ben Hamed, J. R. Duhamel, F. Bremmer, & W. Graf, 2002; C. E. Connor, J. L. Gallant, D. C. Preddie, & D. C. Van Essen, 1996; C. E. Connor, D. C. Preddie, J. L. Gallant, & D. C. Van Essen, 1997; T. Womelsdorf, K. Anton-Erxleben, F. Pieper, & S. Treue, 2006). This distortion in the retinotopic distribution of receptive fields might cause distortions in spatial perception such as an increase of the perceived size of attended stimuli. Here we test for such an effect in human subjects by measuring the point of subjective equality (PSE) for the perceived size of a neutral and an attended stimulus when drawing automatic attention to one of two spatial locations. We found a significant increase in perceived size of attended stimuli. Depending on the absolute stimulus size, this effect ranged from 4% to 12% and was more pronounced for smaller than for larger stimuli. In our experimental design, an attentional effect on task difficulty or a cue bias might influence the PSE measure. We performed control experiments and indeed found such effects, but they could only account for part of the observed results. Our findings demonstrate that the allocation of transient spatial attention onto a visual stimulus increases its perceived size and additionally biases subjects to select this stimulus for a perceptual judgment.

Cross-modal attention enhances perceived contrast

“…By computing the contrast that is necessary for the attended stimulus to match the apparent contrast of the unattended stimulus, this paradigm allows one to measure the change that attention effects on the perceived contrast of a stimulus. This paradigm, coupled with control experiments, has ruled out alternative cue bias and response bias explanations (9,(12)(13)(14)(15)(16)(17)(18).…”

“…Using this paradigm, studies have shown that exogenous attention alters our subjective impression of many dimensions of spatial and temporal vision: e.g., contrast (9,(12)(13)(14), spatial resolution (15), color saturation (16), size of moving patterns (17), and speed (18). However, the issue continues to be debated (19,20).…”

Transient covert attention does alter appearance: A reply to Schneider (2006)

“…Using this paradigm, it has been reported that attention alters our subjective impression of many dimensions: contrast appearance (Carrasco, Ling, & Read, 2004;Hsieh et al, 2005), spatial frequency and gap size (Gobell & Carrasco, 2005), flicker rate (Montagna & Carrasco, 2006), motion coherence (Liu et al, 2006), size of a motion stimulus (Anton-Erxleben, Henrich, & Treue, 2007), perceived speed (Turatto et al, 2007), and color saturation (but not hue; . For a review, see Carrasco (2007).…”

“…We implemented a paradigm that allowed us to measure perceived contrast without asking observers to do so directly. Moreover, because our observers performed an orientation discrimination task contingent upon appearance, we had an objective index indicating that the observers were performing the task and that the cue was effective (Anton-Erxleben et al, 2007;Carrasco, Ling, & Read, 2004;Liu et al, 2006). Many have commented on the strengths of this simple paradigm (Luck, 2004;Treue, 2004).…”

Are the effects of attention on speed judgments genuinely perceptual?

“…Exogenous attention has also been reported to alter the perceived coherence (Liu, Fuller, & Carrasco, 2006), size (Anton-Erxleben, Henrich, & Treue, 2007), and speed (Turatto, Vescovi, & Valsecchi, 2007) of moving objects.…”