Schmidtmann, G., Jennings, B. J., Bell, J., & Kingdom, F. A. A. (2015). Probability, not linear summation, mediates the detection of concentric orientation-defined textures. Journal of Vision, 15(16):6, 1–19, PDF
Gunnar Schmidtmann, Ben J. Jennings, Frederick A.A. Kingdom
Visual objects are effortlessly recognized from their outlines, largely irrespective of viewpoint. Previous studies have drawn different conclusions regarding the importance to shape recognition of specific shape features such as convexities and concavities. However, most studies employed familiar objects, or shapes without curves, and did not measure shape recognition across changes in scale and position. We present a novel set of random shapes with well-defined convexities, concavities and inflections (intermediate points), segmented to isolate each feature type. Observers matched the segmented reference shapes to one of two subsequently presented whole-contour shapes (target or distractor) that were re-scaled and re-positioned. For very short segment lengths, performance was significantly higher for convexities than for concavities or intermediate points and remained constant with increasing segment length. For concavities and intermediate points, performance improved with increasing segment length reaching convexity performance only for long segments. No significant differences between concavities and intermediates were found. These results show for the first time that closed curvilinear shapes are encoded using the positions of convexities, rather than concavities or intermediate regions. A shape-template model with no free parameters gives an excellent account of the data.
Schmidtmann, G., Jennings, B. J., & Kingdom, F. A. A. (2015). Shape recognition: convexities, concavities and things in between. Scientific Reports, 5, 17142. http://doi.org/10.1038/srep17142 PDF
The Royal Victoria Hospital.
The Montreal General Hospital
Kingdom, F. A. A., Baldwin, A. S., Schmidtmann, G. (2015) Modeling probability and additive summation for detection across multiple mechanisms under the assumptions of signal detection theory. Journal of Vision, Vol.15, 1. doi:10.1167/15.5.1 PDF
Schmidtmann, G., Logan, A.J., Kennedy, G.J., Gordon, G.E. Loffler, G. (2015), Distinct lower visual field preference for object shape. Journal of Vision (2015) 15(5):18, 1–15 PDF
Hint: Both towers are identical.
Marouane Ouhnana created this dynamic version of the famous Leaning-Tower Illusion. (Kingdom, F. A. A., Yoonessi, A. & Gheorghiu, E. (2007). The Leaning Tower illusion: a new illusion of perspective. Perception, 36, 475-477.)
All lines are straight and the background is a uniform grey (Schmidtmann & Jennings, 2014).
