Perceptual mechanisms underlying human click-based echolocation

Echolocation is an active sensing strategy used by some blind individuals to navigate their surroundings. Human echolocators emit tongue clicks, leveraging the echoes to detect, discriminate, and localize objects within their environment. Proficient blind echolocators outperform non-expert blind and sighted individuals in most echo-acoustic tasks; while visual experience and expertise play significant roles in echolocation performance, the underlying mechanisms of this advantage remain unclear. Recent research from our lab suggests that the emitted click masks the subsequent fainter echo, and superior performance among experts may be attributed to a more effective release from masking relative to novices. We explore this hypothesis by evaluating the influence of two aspects of masking on echolocation performance: click-echo signal-to-noise ratio (SNR) and click-echo temporal separation. Novice-sighted individuals completed an echo-acoustic localization task. Each trial consisted of 2, 5, 8, or 11 synthesized mouth clicks with spatialized echoes from reflectors 1-meter away and 5°–25° from the midsagittal plane. Participants indicated the reflector’s location (left vs. right). In Experiment 1, the click amplitude was variably attenuated relative to its natural amplitude. In Experiment 2, click amplitude was fixed while the click-echo time delay varied from ~6–60 ms, equivalent to 1–10 meters. We hypothesized that performance would improve as click-echo amplitude attenuates (Exp. 1) and click-echo time delay increases (Exp. 2). Our results revealed that novice-sighted individuals, at echo-click-level-difference > -2 dB or click-echo time delay > 52 ms, performed similarly to proficient echolocators presented with naturalistic stimuli (~25 dB; ~6 ms). These findings suggest that a well-tuned click-echo relationship, alongside an optimized click-echo temporal integration window, enhances echolocation performance. Future research will explore their combined or separate roles in auditory filters. Finely tuned click-echo SNRs and a narrower click-echo temporal integration window may underlie echolocation proficiency due to improved click-echo segregation and echo representation.