No abstract

Echolocating organisms represent their external environment using reflected auditory information from emitted vocalizations. This ability, long known in various non-human species, has also been documented in some blind humans as an aid to navigation, as well as object detection and coarse localization. Surprisingly, our understanding of the basic acuity attainable by practitioners—the most fundamental underpinning of echoic spatial perception—remains crude. We found that experts were able to discriminate horizontal offsets of stimuli as small as ~1.2° auditory angle in the frontomedial plane, a resolution approaching the maximum measured precision of human spatial hearing and comparable to that found in bats performing similar tasks. Furthermore, we found a strong correlation between echolocation acuity and age of blindness onset. This first measure of functional spatial resolution in a population of expert echolocators demonstrates precision comparable to that found in the visual periphery of sighted individuals.

No abstract

We examined how expectation influences perception of complex objects. Participants discriminated between normal and distorted images of famous faces or places. Word cues (mostly valid) indicated either the general category or the exact identity of the upcoming image pair. Whereas category cues did not affect performance, valid exemplar expectation led to performance benefits. Furthermore, discrimination was slower after exemplar cues from the incorrect category than after invalid exemplar cues from the correct category, indicating costs of invalid category expectation. Thus, expectation of a specific exemplar facilitates perception of that object, but hinders perception of an object from a different category.