Exploring how object shape and binocular vision interact to make or break camouflage

Depth perception;Movement, Psychology of;Camouflage (Biology)

Cammack, Philip ; Harris, Julie ; Harris, Julie

University:University of St Andrews

Department:Psychology & Neuroscience (School of)

关键词: Depth perception;    Movement, Psychology of;    Camouflage (Biology);   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/16624/PCammackPhDThesis.pdf?sequence=2&isAllowed=y

来源: DR-NTU

【 摘 要 】

Depth perception is a major component of 3D vision. There are many cues to depth; oneparticularly sensitive aspect is the vivid perception of depth created from having eyes withoverlapping visual fields (binocular vision). As the eyes are located at different points inspace, they see different views of the scene – these slight differences (called binoculardisparity) can be used to obtain depth information. However, extracting depth fromdisparity requires complex visual processing. So why use binocular vision?Julesz (1971) proposed an explanation – camouflaged animals can fool the perception ofsome cues to 3D shape, but camouflage is ineffective against binocular vision. We wouldexpect that animals with binocular vision could see the 3D shape of animals, despite theircamouflage.Whilst commonly accepted, this hypothesis has not been tested in detail. Inthis thesis, we present experiments designed to establish how depth from binocular visioninteracts with camouflage and object shape. Two main questions were addressed:First, we explored how the visual system represented depth information about 3D objectsfrom binocular disparity. Objects with smooth depth edges (hill-shaped) were perceivedwith less depth than sharper edged objects. A computational model that segregated theobject, then averaged the disparity over the segregated region emulated humanperformance. Finally, we found that disparity and luminance cues interacted to alterperceived depth.Secondly, we investigated if binocular vision could overcome camouflage. We found thatcamouflaged objects defined by luminance were detected faster when also defined bydepth from disparity, thus reduces the effect of camouflage. Smooth objects were detectedslower than sharp objects: an effect that was replicated in the real world, suggesting acamouflage technique to counter binocular vision.In summary, binocular vision is useful because it can detect camouflaged objects. However,smoother shapes take longer to spot, forming binocular (or stereoscopic) camouflage.