Weighted combination of size and disparity: a computational model for timing a ball catch

Abstract

How do we time hand closure to catch a ball? Binocular disparity and optical looming provide two sources of information about an object's motion in depth, but the relative effectiveness of the two cues depends on ball size. Based on results from a virtual reality ball-catching task, we derive a simple model that uses both cues. The model is sensitive to the relative effectiveness of size and disparity and implicitly switches its response to the cue that specifies the earliest arrival and away from a cue that is lost or below threshold. We demonstrate the model's robustness by predicting the response of participants to some very unusual ball trajectories in a virtual reality task.

Spatially constrained locomotion under informational conflict

“…Since the present study revealed an over-expansion effect in combination with the lack of an under-expansion effect, the variable that specified the shortest TTP actually had a greater effect on locomotor pointing control. Taken together, the present results are in line with the Rushton and Wann study [14], since they support these autors' ecologically valid, early responding strategy. In addition, it appears that our findings grant this strategy a broader scope, because they extend the so-called security principle to goal-directed actions.…”

“…Another important aspect of the nervous system's adaptability was put forward by Rushton and Wann [14], who showed that when two variables specifying time-to-contact (TTC) are in conflict, the variable indicating the shortest TTC has a greater impact. As these authors stated, in an ecological context, responding early is often preferable to responding late ( [14], p. 190).…”

“…As these authors stated, in an ecological context, responding early is often preferable to responding late ( [14], p. 190). In the present experiment, TTP ih and TTP h were in fact conflicting.…”

Stereo vision enhances the learning of a catching skill

“…1 There is a wealth of indirect evidence for the use of stereo vision in interceptive behaviour from studies with a monocular/binocular paradigm or from studies using a telestereoscope or virtual reality (Rushton and Wann 1999;Judge and Bradford 1988;van der Kamp et al 1999). However, covering one eye implies the loss of more than stereo vision alone since concordant information is also absent.…”

The contribution of stereo vision to one-handed catching

“…However, tau alone does not seem to be sufficient. Several authors have demonstrated in both theoretical (Laurent et al 1996) and experimental ways (Rushton and Wann 1999;van der Kamp et al 1999) that binocular information sources such as retinal disparity, and more specifically the tau function of disparity, can be involved as well. In order to unravel which of these visual information sources, tau or disparity, is used in the timing of interceptive actions, visual conditions in people with normal visual abilities have been artificially manipulated in different ways.…”