Perception and discrimination as a function of stimulus orientation: The "oblique effect" in man and animals.

Abstract

Performance for a large variety of perceptual tasks is superior for stimuli aligned in horizontal or vertical orientations, as compared to stimuli in oblique orientations. This phenomenon appears in the human adult and child, and throughout the animal kingdom. Neurophysiological mechanisms for orientation analysis have been found in the higher visual pathways of many animals, and the suggestive evidence is compelling that these mechanisms underly the orientation preferences reported behaviorally. This paper reviews both the behavioral and neurophysiological studies of orientation preferences, and suggests additional methods for determining the cause of these effects. Stimulus orientation has received increased attention in the past decade from neurophysiological studies of visual pathways. These studies have located mechanisms for orientation analysis in single cells of mammalian visual systems. The study of stimulus orientation, however, has a long history in the behavioral and psychophysical literature. A persistent feature of these latter studies has been a small but consistent superiority in performance when visual stimuli are horizontal or vertical, as opposed to oblique. (For convenience, this phenomenon is subsequently referred to as the oblique effect.) The origin of the oblique effect has not been precisely determined, but a relationship between the behavioral results and the neurophysiological data is suggestive. This paper deals with the oblique effect in two parts. First, it reviews the behavioral and psychophysical studies of orientation preferences. Second, it discusses the neurophysiological substrates of orientation perception. The first section helps define the oblique effect by elaborating on the many forms in which it appears. The second section amplifies the first by evaluating the neurophysiological findings in respect to these orientation preferences.

No evidence for surface organization in Kanizsa configurations during continuous flash suppression

“…All in all, an account based on the features present in the individual elements and across the configuration as a whole seems to offer the most likely explanation for the effects of configuration observed here and in Experiment 1. Reflecting retrospectively on our results, it is worth pointing out that the visual system is most sensitive to cardinal orientations (horizontal and vertical) and less so to oblique ones (Appelle, 1972;Campbell & Kulikowski, 1966;Li et al, 2003;Yacoub et al, 2008). From this perspective, the configuration effects observed in both experiments could be explained potentially by the differences between the orientations most prominently present in the stimuli, at the spatial scales of the individual elements and of the configuration as a whole.…”

“…Alternatively, the observed advantage for the standard configuration could be due to independent contributions of the single elements comprising the configuration, based on their individual locations in the visual field and their orientation. For example, we know that observers are more sensitive to cardinal (horizontal and vertical) orientations compared with oblique ones (Appelle, 1972;Campbell & Kulikowski, 1966) and that these cardinal orientations are over-represented in the visual cortex (Li, Peterson, & Freeman, 2003;Yacoub, Harel, & Ugurbil, 2008). Thus, it could be that differences in the number of different orientations are directly influencing suppression strength.…”

Selective interhemispheric circuits account for a cardinal bias in spontaneous activity within early visual areas

“…A cardinal bias in cortical structures goes along with improved psychophysical performance for cardinal contours in humans (Appelle, 1972;Orban et al, 1984) and monkeys (Boltz et al, 1979;Krebs et al, 2000), known as the oblique effect. In agreement, cells responding to cardinal orientations respond more vigorously (cats: Pettigrew et al, 1968;Frégnac and Imbert, 1978;Orban et al, 1981;Leventhal and Schall, 1983;monkeys: Mansfield and Ronner, 1978;Blakemore et al, 1981) and are greater in number (Li et al, 2003).…”

Superior orientation discrimination and increased peak gamma frequency in autism spectrum conditions.

“…WASI T-scores were correlated with oblique orientation discrimination thresholds (r=-.362, p=.003), but not induced peak gamma frequency (r=.11, p=.39). Given that performance for vertical stimuli is superior than that for cardinal stimuli (Appelle, 1972), it is likely that vertical orientation discrimination thresholds may lead to ceiling effects in both groups, and thus lack the adequate sensitivity to detect group…”