title: Reaching to virtual targets: The oblique effect reloaded in 3-D.
abstract: Perceiving and reproducing direction of visual stimuli in 2-D space produces the visual oblique effect, which manifests as increased precision in the reproduction of cardinal compared to oblique directions. A second cognitive oblique effect emerges when stimulus information is degraded (such as when reproducing stimuli from memory) and manifests as a systematic distortion where reproduced directions close to the cardinal axes deviate toward the oblique, leading to space expansion at cardinal and contraction at oblique axes. We studied the oblique effect in 3-D using a virtual reality system to present a large number of stimuli, covering the surface of an imaginary half sphere, to which subjects had to reach. We used two conditions, one with no delay (no-memory condition) and one where a three-second delay intervened between stimulus presentation and movement initiation (memory condition). A visual oblique effect was observed for the reproduction of cardinal directions compared to oblique, which did not differ with memory condition. A cognitive oblique effect also emerged, which was significantly larger in the memory compared to the no-memory condition, leading to distortion of directional space with expansion near the cardinal axes and compression near the oblique axes on the hemispherical surface. This effect provides evidence that existing models of 2-D directional space categorization could be extended in the natural 3-D space.
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute, 2 Soranou Efessiou, Athens GR 15601, Greece; School of Applied Mathematics and Physical Sciences, National Technical University of Athens, 9 Iroon Politehniou, Athens GR 15780, Greece.
authors.forename: Christos
authors.initials: C
authors.lastname: Kaspiris-Rousellis
authors.affiliation: School of Applied Mathematics and Physical Sciences, National Technical University of Athens, 9 Iroon Politehniou, Athens GR 15780, Greece.
authors.forename: Constantinos I
authors.initials: CI
authors.lastname: Siettos
authors.affiliation: Neurology Department, National and Kapodistrian University of Athens, Eginition Hospital, 72 V. Sofias, Athens GR 15231, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Evdokimidis
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute, 2 Soranou Efessiou, Athens GR 15601, Greece; Psychiatry Department, National and Kapodistrian University of Athens, Eginition Hospital, 72 V. Sofias, Athens GR 15231, Greece. Electronic address: smyrnis@med.uoa.gr.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Smyrnis
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001132:Arm; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D011601:Psychophysics; D013028:Space Perception; D065852:Spatial Memory; D014584:User-Computer Interface; D014796:Visual Perception; D055815:Young Adult
keywords: direction perception; oblique effect; reaching movements; spatial memory; spatial representation