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Does edge enhanced camouflage disrupt slant perception through surface continuity conflicts? Callum Wilson, School of applied sciences email: c.wilson1700@abertay.ac.uk
Introduction:
• Unified perceptual representations are formed using multiple separate depth cues without any one cue offering true depth. • Depth from disparity using the difference between the two eyes retinal images to detect depth difference increases predator's ability to detect camouflaged prey (Adams et al. 2019). • Camouflage may target cue combination process by using luminance information that conflicts with depth from disparity information and disrupts surface features that are important in depth from disparity formation (Cammack & Harris, 2016; Marr & Poggio, 1979). • This experiment implemented a two alternative forced choice (2AFC) paradigm in Virtual reality (HTC VIVE) that used slanted surfaces visible through an aperture (see fig. 1). The motivation for this was to provide a rigorous yet ecologically valid measure of depth perception.
• Hypothesis 1: Perceptual sensitivity will be reduced when depth from disparity information is eliminated. • Hypothesis 2: Positive edge enhancement will reduce the perceptual sensitivity compared to flat disruptive camouflage • Hypothesis 3: Negative edge enhancement will reduce the perceptual sensitivity compared to positive edge enhancement
Fig. 2. Left: flat disruptive camouflage, Middle: Positive edge enhanced disruptive camouflage, Right: Negative edge enhanced disruptive camouflage.
Participants and Procedure: Fig.1 Left: image of the camouflage textures in relation to the participant. Right: Top-down view of the experiment showing the slanted surfaces.
Stimuli and Hypotheses:
• Positive edge enhancement where the lighter areas of a camouflage pattern are lighter and darker areas are darker at their boundaries (fig. 2) has been shown to increase camouflage effectiveness (Osorio & Srinivasan, 1991). We included “flat” disruptive camouflage textures and positively edge enhanced textures.
• 7 participants have currently taken part in this experiment. • Participants were presented with two slanted surfaces visible through an aperture (Fig. 1) and instructed to select the surface that was most slanted to the right by “zapping” it with the HTC VIVE hand controller. A checkerboard surface was used as a control (see Fig. 1). • The experiment was run using the same camouflage patterns twice for each participant once in a binocular viewing condition and one in a monocular viewing condition (where one eye was blocked using an eyepatch). References: Adams, W. J., Graf, E. W., & Anderson, M. (2019). Disruptive coloration and binocular disparity: breaking camouflage. Proceedings of the Royal Society B, 286(1896), 20182045. doi: https://doi.org/10.1098/rspb.2018.2045 Cammack, P., & Harris, J. M. (2016). Depth perception in disparity-defined objects: finding the balance between averaging and segregation. Philosophical Transactions of the Royal Society B: Biological Sciences, 371(1697), 20150258. doi: https://doi.org/10.1098/rstb.2015.0258 Knill, D. C., & Pouget, A. (2004). The Bayesian brain: the role of uncertainty in neural coding and computation. TRENDS in Neurosciences, 27(12), 712-719. doi: https://doi.org/10.1016/j.tins.2004.10.007 Marr, D., & Poggio, T. (1979). A computational theory of human stereo vision. Proceedings of the Royal Society of London. Series B. Biological Sciences, 204(1156), 301-328. Landy, M. S., Maloney, L. T., Johnston, E. B., & Young, M. (1995). Measurement and modeling of depth cue combination: in defense of weak fusion. Vision research, 35(3), 389-412. doi: https://doi.org/10.1016/0042-6989(94)00176-M Abertay University is an operating name of the University of Abertay Dundee, a charity registered in Scotland, No: SC016040. Linares, D., & López-Moliner, J. (2016). quickpsy: An R package to fit psychometric functions for multiple groups. The R Journal, 2016, vol. 8, num. 1, p. 122-131. Penacchio, O., Harris, J. M., & Lovell, P. G. (2017). Establishing the behavioural limits for countershaded camouflage. Scientific reports, 7(1), 1-11. doi: https://doi.org/10.1073/pnas.1611589113 Prins, N. (2016). Psychophysics: a practical introduction. Academic Press. Tankus, A., & Yeshurun, Y. (2000, September). Convexity-based camouflage breaking. In Proceedings 15th International Conference on Pattern Recognition. ICPR-2000 (Vol. 1, pp. 454-457). IEEE. doi: https://doi.org/10.1109/ICPR.2000.905374
Preliminary data interpretation:
• Hypothesis 1: The slope of monocular trials (representing sensitivity) appears to be lower than the slope of the binocular trials. • Hypothesis 2: The slope of the positive EE trials appears to be slightly lower than the slope of the flat disruptive camouflage trials. • Hypothesis 3: The slope of the negative EE trials appears to be lower than the slope of the positive EE trials