Isoeccentric locations are not equivalent: The extent of the vertical meridian asymmetry

Abstract

Performance in visual tasks is limited by the low-level mechanisms that sample the visual field. It is well documented that contrast sensitivity and spatial resolution decrease as a function of eccentricity and that those factors impair performance in “higher level” tasks, such as visual search. Performance also varies consistently at isoeccentric locations in the visual field. Specifically, at a fixed eccentricity, performance is better along the horizontal meridian than the vertical meridian, and along the lower than the upper vertical meridian. Whether these asymmetries in visual performance fields are confined to the vertical meridian or extend across the whole upper versus lower visual hemifield has been a matter of debate. Here, we measure the extent of the upper versus lower asymmetry. Results reveal that this asymmetry is most pronounced at the vertical meridian and that it decreases gradually as the angular distance (polar angle) from the vertical meridian increases, with eccentricity held constant. Beyond 30° of polar angle from the vertical meridian, the upper to lower asymmetry is no longer reliable. Thus, the vertical meridian is uniquely asymmetric and uniquely insensitive. This pattern of results is consistent with early anatomical properties of the visual system and reflects constraints that are critical to our understanding of visual information processing.

Attention searches nonuniformly in space and in time

“…This effect was observed in both hemifields. This type of visual field asymmetry has been reported previously (19)(20)(21)(22). As a result, two probe locations, even adjacent, might present different report probabilities (i.e., P1 > P2) due to a position bias, rather than the kind of attentional effect under investigation here (one might speculate as to whether the position bias is, in turn, due to an attentional effect or some other spatially variable aspect of visual processing, but this question is beyond the scope of this investigation).…”

“…A study in the macaque monkey showed that neurons in the frontal eye field respond sequentially to the items of a difficult search task, at a frequency of [18][19][20][21][22][23][24][25]. This finding was the first strong evidence of a link between attentional periodicity and sequential processing in visual search.…”

Variations in crowding, saccadic precision, and spatial localization reveal the shared topology of spatial vision

“…Contrary to recent suggestions that crowding and saccades are closely linked (37)(38)(39), four aspects of our data lead us to reject an inextricable linkage between these processes. First, although crowding and saccades show similar patterns of variation, saccadic precision is worse in the lower visual field than in the upper-the opposite pattern not only to crowding, but also to a wide range of perceptual tasks (24,25). Second, our participants were clearly able to trade their precision between the two processes; saccadic precision was highest in trials where crowded identification was incorrect and vice versa.…”

“…Eye movements are similarly affected -both the distribution of landing errors for saccadic eye movements (20) and the detection of position shifts in saccadic targets (21) show these characteristics. Additionally, as with crowding, performance is worse in the upper than in the lower visual field for gap resolution and Vernier acuity (22,23), along with a range of other spatial identification measures (24,25) that similarly show worse performance along the vertical than the horizontal meridian.…”

Evaluating Amazon’s Mechanical Turk for psychological research on the symbolic control of attention

“…The left/right advantage is thought to reflect the asymmetrical organization of the human visual system (Abrams, Nizam, & Carrasco, 2012;Carrasco, 2014;Kobayashi & Kohshima, 1997, 2001aNomura, Katahata, & Hashiya, 2005;Ossandón, Onat, & König, 2014;Pauszek & Gibson, 2016; see also Robertson, 2004, for a review). In the context of the spatial cuing paradigm, the left/right advantage manifests as faster RTs due to more efficient target processing when the target appears at the left or right location, relative to when the target appears at the above or below location.…”