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A Biological Perspective

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A Biological Perspective A Biological Perspective: The Effects of Line Style on Arc Curvature Perception Author: Thomas E Boggs Advisor: Greg Elvers PhD Introduction Results Discussion • Schmidtmann et al. (2016) explains that curvature • A univariate repeated measures analysis of variance (ANOVA) was • When examining the effects of line style, all of the can be misperceived in many circumstances. used to compare the effect of the 2 (line style) x 3 (arc radius) x 3 conditional means are in the expected direction • Virsu (1971) found that perceived curvature was (arc length) experiment on veridical curve judgements. except for the arc with the smallest radius and often underestimated. He varied the length and 250 shortest length. orientation of the arcs. • Main effect of arc length, F(1.16, • Overall, the results do not support hypothesis 1, 2 200 • Why does the misperception of the arcs occur? 53.36)= 28.62, p= .001, ηp= .38. however they do support hypothesis 2. After examining contextual information, we believe • Main effect of arc radius, F(1.35, 150 • The interaction of the Radius and Line Style is an 2 100 there may be a biological cause – V4 neurons tuned 61.90)= 335.37, p= .001, ηp= .879. important finding. This interaction, paired with to curvature may respond less to shorter arcs than • No main effect of line style, F(1, 50 subsequent data analysis, suggests hypothesis 1 is Perceived Radius (pixels) Radius Perceived 185.52 203.35 to longer arcs. 46)= 2.12, p= .153 , η2= .04. 0 supported at the 300 pixel arc radius level and it p Dotted Solid • The ventral pathway, which is responsible for color Line Style reveals a marginal significance at the 200 pixel level. 300 • and shape, includes both V1 and V4 cortical areas 250 250 After re-evaluating the design of the trials, we (Connor et al., 2007). The output of V4 depends on 200 200 believe the spacing of the dots may be affecting the the amount of excitation from V1 (Yantis, 2013). 150 150 way the participant judges the dotted arcs. Spacing • By manipulating line style (dotted vs solid), arc 100 100 of the dots varies from 9 (smallest radius and 50 50 136.69 199.29 247.31 radius, and arc length, we should better understand 226.05 183.97 173.28 (pixels) Radius Perceived shortest length) to 78 (largest radius and longest 0 0 why the misperception occurs. (pixels) Radius Perceived 20° 40° 60° 100 200 300 length) pixels apart depending on the trail. Arc Radius (pixels) Arc (interior angle) Length • Future research will focus on dotted trials with Hypothesis • Significant interaction of Length x Radius F(3.06, 140.60)= 5.69, p= equal spacing. We believe that by making the dots a 2 1. The dotted arc should be perceived as less curved .001, ηp= .11. uniform distance apart a main effect of line style than the solid arc with the same length and radius • Significant interaction of Radius x Line Style F(1.34, 61.90)= 7.36, will be observed. 2 because dots should lead to less activation of V1 p= .004, ηp= .14. orientation detectors which send information to V4 300 References curvature detectors. 250 Connor, C. E., Brincat, S. L., Pasupathy, A. (2007). 2. Perceived curvature of the arc should be more 200 Transformation of shape information in the ventral veridical when the arc is longer and has a larger pathway. Current opinion in Neurobiology, 17, 140- 150 radius. 147. http://dx.doi.org/10.1016/j.conb.2007.03.002 100 Method Schmidtmann, G., Ouhnana, M., Loffler, G., & 50 Kingdom, F. A. (2016). Imagining circles—Empirical Perceived Radius of Arc (pixels) of Arc Radius Perceived 137.18 136.22 186.84 211.74 232.53 262.07 • Participants: 48 participants with a mean age of 0 data and a perceptual model for the arc-size illusion. 20.00 years (SD=1.89) were used (24 male). 100 200 300 Actual Arc Radius (pixels) Vision Research, 121, 50-56. • IV 1 Line Style: Arc style was dotted or solid. Dotted Solid http://dx.doi.org/10.1016/j.visres.2015.12.003 • IV 2 Arc Radius: Arc radius was small, med. or large. • Subsequent testing of the Radius x Line Style interaction revealed Yantis, S. (2013).The visual brain, & Recognizing visual • IV 3 Arc Length: Arc length was short, med. or long. • At 300 Pixels: A simple main effect of Line Style, F(1, 46)= 5.56, objects. Sensation and perception. Palgrave • 2 Procedure: Participants were first randomly p= .023, ηp= .11. Macmillan. assigned to the dotted line or solid line group and • At 200 Pixels: A marginal simple main effect of Line Style, F(1, Virsu, V. (1971). Underestimation of curvature and then saw 9 conditions (factorial combination of the 2 46)= 3.49, p= .068, ηp= .07. task dependence in visual perception of form. other IVs) repeated 5 times with 30 second breaks • At 100 Pixels: No simple main effect of Line Style. F(1, 46)= .005, Perception & Psychophysics, 9, 339-342. between each repetition. p= .95, η2= .00. http://dx.doi.org/10.3758/bf03212661 • Task: Adjust size of comparison circle so curvature p of circle and arc perceptually matched. Contact: Thomas Boggs, [email protected].
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