Base on balls for the Chapman strategy: Reassessing Brouwer, Brenner, and Smeets (2002)

Abstract

A true understanding of skilled behavior includes the identification of the information that underlies the perception–action cycle at work. Often, observers’ sensitivity to perceptual variables is established in laboratory-situated simulation-based psychophysical experiments. The observers’ sensitivity thus determined is then used to draw conclusions that will generalize the findings to natural behavior. Focusing on the example of running to catch fly balls, the present contribution takes the study of Brouwer, Brenner, and Smeets (Perception & Psychophysics 64:1160–1168, 2002) to illustrate how common assumptions in the steps from psychophysical experiments to natural behavior can result in ungrounded conclusions. These authors built an argument to reject the use of the Chapman strategy of zeroing out optical acceleration. For this argument, they determined the sensitivity of the visual system to acceleration, assuming that acceleration is detected as a velocity ratio. Next, they showed that catchers started running earlier than could be expected on the basis of sensitivity thresholds for this velocity ratio, concluding that running initiation could not have been based on optical acceleration. In the present study, we argue that important assumptions in the Brouwer et al. (Perception & Psychophysics 64:1160–1168, 2002) line of argument are incorrect. First, we show how the assumption of parabolic ball flight trajectories, although convenient, biased Brouwer et al.’s (Perception & Psychophysics 64:1160–1168, 2002) conclusion. Next, we present an experiment revealing that observers do not base their judgments of acceleration on the velocity ratio. Thus, we demonstrate that Brouwer et al.’s (Perception & Psychophysics 64:1160–1168, 2002) argument that optical acceleration cannot serve as the information for running to catch fly balls does not hold.

Keeping Your Eyes Continuously on the Ball While Running for Catchable and Uncatchable Fly Balls

“…Because of drag and spin, fly balls do not follow parabolic trajectories (cf. [1] , [8] , [11] ), which implies that a sophisticated internal model of ball-flight dynamics would have to be postulated.…”

Gravity and Known Size Calibrate Visual Information to Time Parabolic Trajectories

“…Given that parabolic trajectories move accelerated by terrestrial gravity, it is reasonable to consider humans’ ability to detect acceleration. Calderone and Kaiser ( 1989 ) proposed that acceleration in the visual system can be studied as the rate of change in speed divided by the average object speed in a two-stage process carried out in about 200 ms (Werkhoven et al, 1992 ; Zaal et al, 2012 ). This delay would mean that the observer would not continuously monitor the adequacy of their actions.…”

“…This delay would mean that the observer would not continuously monitor the adequacy of their actions. Furthermore, some studies found that it is necessary at least ~20% of the change in speed to detect acceleration (Gottsdanker et al, 1961 ; Werkhoven et al, 1992 ; Babler and Dannemiller, 1993 ; Brouwer et al, 2006 ; Zaal et al, 2012 ) indicating that humans are quite insensitive to changes in speed.…”

“…In our view, drawing predictions based on prior knowledge is not just a reliable and accurate way to predict future states of the environment but also helps us override the need to use unreliable optic cues (Cutting and Vishton, 1995 ). For instance: expansion rate ( ) and thus Tau ( τ ) might not be available at large distances, optic acceleration ( ) is hardly discriminable by humans and would not allow for the continuous control of action (Werkhoven et al, 1992 ) even though some studies claim that the values of optical acceleration available are large enough to be detected (Babler and Dannemiller, 1993 ; Zaal et al, 2012 ); lastly, the literature is mixed with regards to the benefits of providing binocular disparity. Because of these reasons, here we advocate using the rate of change in the elevation angle ( ), which is very precise, in combination with an internalized knowledge of gravity and physical size for the estimation of TTC in the GS model.…”

Optical angular constancy is maintained as a navigational control strategy when pursuing robots moving along complex pathways

“…As shown in Figure 1a, the optical ball trajectory can be compared to that of an imaginary elevator rising from the home plate at a constant velocity and tilted by the amount that fielders run forward or backward (Babler & Dannemiller, 1993;McLeod & Dienes, 1993, 1996McLeod, Reed, & Dienes, 2003, 2006Michaels & Oudejans, 1992). Although some work examining acceleration discrimination has questioned OAC (Brouwer, Brenner, & Smeets, 2002;Zaal, Bongers, Pepping, & Bootsma, 2012), other Citation: Wang, W., McBeath, M. K., & Sugar, T. G. (2015). Optical angular constancy is maintained as a navigational control strategy when pursuing robots moving along complex pathways.…”