Egocentric distance estimation in motion: comparison of two psychophysical methods

Abstract

The perception of the space surrounding us is one of the most relevant problems that our brain faces at

every moment, because this information is vital to be able to interact correctly with the environment.

There is an important body of literature about distance perception in open field, but these studies are

based on the assumption that most of our visually guided behavior is carried out from an approximately

static position. However, it is a fact that we and the things around us are in continuous movement. The

objective of this experimental work is to study the influence of proprioceptive information in the estimation

of distance under naturalistic conditions, also analyzing the difference between two methods (direct and

indirect) when collecting data. The estimates made by the subjects at 4 distances (12, 18, 24 and 32 m) are

compared in two conditions: one static (vel = 0 km / h) and another one in \proprioceptive movement"

on a treadmill (vel = 8 km / h). Each distance was estimated with both methods. In the indirect method,

each distance was estimated 5 times, randomizing the estimation order. 15 observers participated (9 men,

6 women) between 20 and 27 years old (average = 25 years). When comparing both methods, the results

show that in 63% of the cases the estimation error is reduced with the indirect method. On this method,

the statistical analysis finds significant differences due to the speed (F(1; 480) = 91; 5, p < 0; 001), distance

(F(3; 480) = 1797; 2, p < 0; 001) and the observer (F(14; 480) = 49; 5 , p < 0;001). In both speeds the

compression of the frontal visual space was observed for all the distances, but the error is smaller in the

moving condition, noticing here that although the distance to be estimated increases, the absolute error

remains constant.