Things that go bump in the light: On the optical specification of contact severity.

Abstract

Psychologists are intrigued with the idea that optical variables can specify not only the time until an object impacts an observer but also the severity of the impact. However, the mapping between the optical variables (tau and .tau) and the kinematic variables (velocity, acceleration) has been misstated, erroneously implying that there exist critical values of the optical variables used for locomotion and control. In this commentary, the mathematical relationship between the optical and kinematic variables is reexamined and the erroneous assumptions that have led to the proposal of critical values are show. Also examined are the empirical data on deceleration to approach (particularly from active control paradigms) to assess whether the proposed optical variables are likely candidates for control strategies. Finally, problems associated with numerical approximations to dynamic systems, particularly when analytic solutions exist, are discussed.

The dynamics of perception and action.

“…The data were quite consistent with a strategy, with an overall mean of Ϫ0.51. However, the time series of braking behavior revealed that participants did not hold constant at Ϫ0.5, as some have suggested (Kaiser & Phatak, 1993;Kim, Turvey, & Carello, 1993;Lee, 1976), but rather made a series of brake adjustments at a rate of about one per second. A detailed analysis showed that the direction and magnitude of each adjustment depended upon the current value of .…”

Drift-diffusion explains response variability and capacity for tracking objects

“…Time to contact (TTC), which is the time it takes for an object to reach an observer or a particular place, is an important factor in a variety of real-world situations, such as catching and hitting balls in games, driving vehicles, or passing through a busy street. The ability to estimate TTC for one object has been assessed in several studies (for example see [1][2][3][4][5][6][7][8][9][10][11][12][13][14]). The accuracy and precision of TTC estimation is related to the time perception ability, which is considered in several studies [6,11,[15][16][17][18][19][20][21][22][23][24].…”

Visual cues for manual control of headway

“…Lee's (1976) model of car following is problematic for a number of reasons (e.g., see Kaiser and Phatak, 1993; Wann, 1996; Treslian, 1999; Kaiser and Johnson, 2004). Firstly, there are instances during following events where τ and/or $\dot{\tau }$ either can not be calculated or are required to be held at infinity (e.g., when $\dot{\theta }=0$ or when $\ddot{\theta }=0$).…”