Tau as a potential control variable for visually guided braking.

D. N. Lee (1976) described a braking strategy based on optical expansion in which the driver brakes so that the target's time-to-contact declines around a constant slope in the range -0.5 < or = tau < 0. The present results from a series of braking simulations confirm and extend earlier reports (E. H. Yilmaz & W. H. Warren, 1995) that performance is broadly compatible with the tau hypothesis. However, performance was not enhanced in situations that favored the estimation of tau, and unlike in earlier reports, performance deteriorated in the absence of a ground plane that provided information about speed and target distance. This finding suggests that the tau hypothesis does not provide a complete account of braking control.

A test of the tau-dot hypothesis of braking control in the real world.

A controlled experiment used instrumented vehicles in a real-world driving task to compare D. N. Lee's (1976) tau-dot hypothesis of braking control with an alternative based on the direct estimation and control of ideal deceleration (T. Yates, M. Harris, & P. Rock, 2004). Drivers braked to stop as closely as possible to a visual target from different starting speeds and times-to-contact. The data provided little support for the tau-dot hypothesis, and analysis suggested that braking in the real world is better explained by a direct deceleration strategy.

From constancy and polyfunctionality in perception to the transcendental psychology approach: historical overview of a novel psychological paradigm.

This paper presents an overview of a novel approach called Transcendental Psychology Methodology (TPM), largely inspired by Bach-y-Rita's work and developed by A.I. Mirakyan (1929-1995) and his associates. Beginning with the perceptual constancy problem, in which stimuli do not change perceptually despite variations in their physical characteristics, Mirakyan recognized that contemporary accounts of constancy included both theoretical contradictions and empirical discrepancies. This led him to propose TPM as an alternative to the traditional Product Basis Paradigm (PBP). Whilst PBP focuses upon perceptual phenomena, TPM focuses upon the underlying processes and upon the principles that support the flexibility needed to create complex, coherent representations under different stimulus conditions. The central idea that generative perceptual processes may be universal is grounded in Bach-y-Rita's famous experiments and has important parallels with present day conceptions of the construction of meaning in neurophysiological process. TPM inspired studies of a wide range of perceptual phenomena have so far suggested basic principles that can be applied to all perceptual processes, regardless of their modality. Its new conception of the perception of spatial extent can contribute to our understanding of the visual effects that Bach-y-Rita's blind subjects experience and it may provide a useful general tool for uncovering the psychological principles behind Bach-y-Rita's findings. Because of its axiomatic approach and its focus upon universal, generative processes, TPM may also be useful in other disciplines, e.g., in providing a line between neurophysiological and psychological levels of investigation. It may ultimately serve as a general theory of how sensory experience is created.

Global versus local image expansion in estimating time-to-contact from complex optic flow.

Previous work (Harris and Giachritsis 2000, Vision Research 40 601-611) has shown that, when global and local image expansion are placed in conflict, estimates of time-to-contact (TTC) are based almost exclusively upon global expansion. Here we extend this finding by demonstrating that global image expansion continues to predominate even under conditions that seem more favourable to a local analysis. We added a global rotation to the stimulus so that the global pattern of expansion was distorted while leaving the local expansion unaffected. Even under relatively high rotation rates (30 degrees s(-1)), local expansion continued to have little systematic effect upon estimates of TTC.

The roles of inducer size and distance in the Ebbinghaus illusion (Titchener circles).

Although the Ebbinghaus illusion is commonly used as an example of a simple size-contrast effect, previous studies have emphasised its complexity by identifying many factors that potentially influence the magnitude of the illusion. Here, in a series of three experiments, we attempt to simplify this complexity. In each trial, subjects saw a display comprising, on one side, a target stimulus surrounded by inducers and, on the other, an isolated probe stimulus. Their task was to indicate whether the probe appeared larger or smaller than the target. Probe size was adjusted with a one-up, one-down staircase procedure to find the point of subjective equality between probe and target. From these experiments, we argue that the apparent effects of inducer size are often confounded by the relative completeness of the inducing surround and that factors such as the similarity of the inducers and target are secondary. We suggest a simple model that can explain most of the data in terms of just two primary and independent factors: the relative size of the inducers and target, and the distance between the inducers and the target. The balance between these two factors determines whether the size of the target is underestimated or overestimated.