Time To Contact

When a fly lands on a wall, a human catches a ball, or a pilot lands a plane, motion information about when the approaching object will arrive (time to contact) is necessary to interact successfully with the environment. Low-level measurements of the motion of an approaching object do not by themselves contain information about the absolute distance and velocity of the object. However, absolute knowledge of object distance and velocity is not required to determine the time to contact. David Lee showed that it is possible to calculate the time to contact with an approaching object by measuring the relative expansion rate (the ratio of the size of the object at a given instant to its rate of change of size). He referred to this ratio as t. Humans appear to perform such a calculation and base their estimates of time to contact on the relative expansion rate, t. Psychophysical studies show that human judgments of time to contact increase in proportion to parametric variation in t, despite variations in initial expansion rate. Other studies suggest that certain motor actions are initiated when the time to contact reaches a critical value. For example, flies begin decelerating when the relative rate of expansion reaches a critical value; humans appear to use t to initiate appropriate action during driving and catching or hitting a ball. However, research to date has not identified a neurophysiological correlate of t in primates.

Conquering Fear In The 21th Century

Conquering Fear In The 21th Century

The Ultimate Guide To Overcoming Fear And Getting Breakthroughs. Fear is without doubt among the strongest and most influential emotional responses we have, and it may act as both a protective and destructive force depending upon the situation.

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