Table 1.

Correspondence between the half-size of the object (l), the speed of approach ‖v‖, and the parameter l/‖v‖ characterizing the time course of the angular size on the retina

l/‖v‖ (msec)	l (cm)
	6	8	10	12	14
‖v‖ (m/sec)
2	30	40	50	60	70
4	15	20	25	30	35
6	10	13.3	16.7	20	23.3
8	7.5	10	12.5	15	17.5
10	6	8	10	12	14

In the experiments reported here l/‖v‖ ranged from 5 to 50 msec, corresponding to objects of half-size between 6 and 14 cm for approaching speeds between 2 and 10 m/sec, respectively.