The project investigates three questions:
(a) Can static cues about human body movement influence lower levels of visual motion processing? It has been claimed that static visual cues provided by the pose of a moving body (implied motion) can influence the processing of visual movement. A previous study indicated that adaptation to implied motion can alter the appearance of subsequently viewed moving patterns (Winawer et al., 2008). However the methodology employed in that study allowed the possibility that the reported effects were due to shifts in response bias rather than shifts in perceptual bias (i.e. adaptation; Morgan et al., 2013). The experiments conducted in this project tested whether adaptation to implied motion is due to response bias or to perceptual bias.
(b) How does the brain construct representations of the real-world pace or speed of human actions? Retinal signals provide only partial information about the speed of real-world actions such as human movements, because speed on the retina varies with viewing distance as well as with object speed, yet perceived object speed remains constant (velocity constancy). It is still unclear how the visual system resolves this problem to achieve velocity constancy (Burr and Ross, 1982). The project investigated velocity constancy using an adaptation effect in which the perceived pace of human locomotion changes after viewing videos of speeded-up or slowed-down locomotion.
(c) What are the contributions of perceptual and decisional factors to visual judgements? In the past response/decision bias has often been dismissed as an experimental artefact, but recent research implies that it plays a legitimate role in all visual judgements (Morgan et al., 2013). Our experiments compared the results obtained using the same stimuli but different tasks, to evaluate whether the effects observed in (a) and (b) can be attributed to perceptual or decisional factors.
Burr, D. C., & Ross, J. (1982). Contrast sensitivity at high velocities. Vision Research, 22, 479-484.
Morgan, M. J., Melmoth, D., & Solomon, J. A. (2013). Visual Neuroscience, 30 , 197–206. doi:10.1017/S095252381300045X
Winawer, J., Huk, A. C., & Boroditsky, L. (2008). A motion aftereffect from still photographs depicting motion. Psychological Science, 19(3), 276-83.