Abstract
Some blind people have developed a unique technique, called echolocation, to orient themselves in unknown environments. More specifically, by self-generating a clicking noise with the tongue, echolocators gain knowledge about the external environment by perceiving more detailed object features. It is not clear to date whether sighted individuals can also develop such an extremely useful technique. To investigate this, here we test the ability of novice sighted participants to perform a depth echolocation task. Moreover, in order to evaluate whether the type of room (anechoic or reverberant) and the type of clicking sound (with the tongue or with the hands) influences the learning of this technique, we divided the entire sample into four groups. Half of the participants produced the clicking sound with their tongue, the other half with their hands. Half of the participants performed the task in an anechoic chamber, the other half in a reverberant room. Subjects stood in front of five bars, each of a different size, and at five different distances from the subject. The dimension of the bars ensured a constant subtended angle for the five distances considered. The task was to identify the correct distance of the bar. We found that, even by the second session, the participants were able to judge the correct depth of the bar at a rate greater than chance. Improvements in both precision and accuracy were observed in all experimental sessions. More interestingly, we found significantly better performance in the reverberant room than in the anechoic chamber. The type of clicking did not modulate our results. This suggests that the echolocation technique can also be learned by sighted individuals and that room reverberation can influence this learning process. More generally, this study shows that total loss of sight is not a prerequisite for echolocation skills this suggests important potential implications on rehabilitation settings for persons with residual vision.
Highlights
Echolocation can be compared to a biological sonar used by several kinds of animals: the species most known to adopt this peculiar technique are dolphins and bats
We can see that during the session is an improvement not just in the percentage of correct responses (Fig 2A) that is above the chance level (F(3,18) = 6.97, p
We calculated the average ratio of improvement by dividing the percentage of correct responses of each experimental session by the percentage of correct responses of the training (Fig 3A—a mixed model two-way (3 x 2) ANOVA with within factor Session—training Vs 1st Session Vs 2nd Session—and between factor Type of room—anechoic Vs reverberant room), for the anechoic chamber and the reverberant room, and we found one main effect between the sessions (F(4,18) = 17.03, p < 0.001), but not between the type of rooms (F(4,18) = 0.001, p = 0.98)
Summary
Echolocation can be compared to a biological sonar used by several kinds of animals: the species most known to adopt this peculiar technique are dolphins and bats. Depth Echolocation Task as well as the delay in the time it takes for the sound to arrive to the two ears provide information about the horizontal angle (azimuth) from which the reflected sound waves arrive. Spectral coloration of the reflecting object can provide us with information regarding its nature. With this technique animals are able to live in environments where the visual channel cannot be used as a primary source of spatial information. This permits them to carry out essential activities such as hunting or navigating even in complete darkness
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