Critical bottom-up attentional factors in the handle orientation effect: asymmetric luminance transients and object-center eccentricity relative to fixation

Pixel asymmetry predicts between-object differences in the object-based compatibility effect

“…One possibility is that objects are spatially coded based on their overall pixel asymmetry. According to Kostov and Janyan (2020), pixel asymmetry might elicit spatial CEs due to asymmetric changes in luminance—which has been shown to guide attention (Spehar & Owens, 2012)—during stimulus presentation. Pixel asymmetry often corresponds with feature asymmetry; for example, spouts in Cho and Proctor’s (2011) handle-less teapot stimuli contributed to both pixel asymmetry and feature asymmetry.…”

“…An alternative explanation for centrality effects is that they moderate CEs via shifts in pixel asymmetry (Kostov & Janyan, 2020). Object-centring (see Figure 1, panels B and D) 1 results in objects’ bases mostly (in terms of area) appearing on the handle-contralateral side of fixation.…”

“…Kostov and Janyan (2020) have suggested that the object-centred pan-like stimuli used in Kostov and Janyan (2012, 2015) could have produced NCEs by contributing to handle-contralateral pixel asymmetry. To study this possibility, Kostov presented participants with both pixel-centred (so that an equal number of non-background pixels appeared either side of fixation) and object-centred photograph and silhouette stimuli.…”

“…So far, research supports the idea that handle orientation produces spatial CEs that are, at least in part, responsible for the object-based CE (Cho & Proctor, 2010, 2011, 2013). More recent work shows that centrality (or the method by which objects are horizontally centred on-screen) moderates object-based CEs—sometimes reversing the effect (Kostov & Janyan, 2020; Proctor et al, 2017). Why centrality exerts this effect remains unclear.…”

“…Why centrality exerts this effect remains unclear. One possibility is that centrality moderates object-based CEs insofar as it contributes to the overall asymmetry (i.e., pixel asymmetry ) of the stimulus relative to the centre of the display (Kostov & Janyan, 2015, 2020). That is, pixel asymmetry, which varies according to centrality, might produce Simon-like effects and therefore moderate object-based CEs.…”