Sound Localization Ability in Dogs

Abstract

The minimum audible angle (MAA), defined as the smallest detectable difference between the azimuths of two identical sources of sound, is a standard measure of spatial auditory acuity in animals. Few studies have explored the MAA of dogs, using methods that do not allow potential improvement throughout the assessment, and with a very small number of dog(s) assessed. To overcome these limits, we adopted a staircase method on 10 dogs, using a two-forced choice procedure with two sound sources, testing angles of separation from 60° to 1°. The staircase method permits the level of difficulty for each dog to be continuously adapted and allows for the observation of improvement over time. The dogs’ average MAA was 7.6°, although with a large interindividual variability, ranging from 1.3° to 13.2°. A global improvement was observed across the procedure, substantiated by a gradual lowering of the MAA and of choice latency across sessions. The results indicate that the staircase method is feasible and reliable in the assessment of auditory spatial localization in dogs, highlighting the importance of using an appropriate method in a sensory discrimination task, so as to allow improvement over time. The results also reveal that the MAA of dogs is more variable than previously reported, potentially reaching values lower than 2°. Although no clear patterns of association emerged between MAA and dogs’ characteristics such as ear shape, head shape or age, the results suggest the value of conducting larger-scale studies to determine whether these or other factors influence sound localization abilities in dogs.

Determining Hearing Thresholds in Dogs Using the Staircase Method

“…Therefore, no improvement occurred throughout the procedure, suggesting that the first assessment would have been sufficient to conclusively determine the dogs' thresholds at any given frequency. The lack of significant improvement across the procedure is seemingly in contrast with a previous study of our group, where the staircase method was applied for the determination of sound localization abilities in dogs [29] and where a clear improvement was observed throughout the procedure. However, sound detection and sound localization are processed in separate regions of the auditory cortex, with localization involving a crucial role of non-primary auditory areas [40].…”

“…Another possibility which could explain the broader range reported by the latter is that the procedure used in such a study might not have allowed dogs to reach their maximal sensitivity before termination. Indeed, it is well known that in sensory discrimination tasks exposure may improve the ability of the animal to distinguish different kinds of stimuli [ 32 , 33 , 34 ], and this also applies to dogs in acoustic perception tasks [ 29 ]. In the present study, we looked for changes in performance across the procedure and found no evidence of improvement, suggesting that the number of trials dogs were exposed to when they reached the first threshold (180 to 250) was sufficient to reach their maximal sensitivity.…”

“…Experiments were conducted in a room (5.8 m × 4.7 m) equipped to reduce sound reflection and attenuate outside noise. Details of the setting ( Figure 1 ) and the apparatus ( Figure 2 ) have been described in detail previously [ 29 ]. Briefly, the apparatus consisted of a wire-mesh structure, at the center of which a soft headrest was positioned.…”

“…After the dog’s familiarization with the setting and the experimenter, preliminary training was performed as described by Guérineau and colleagues [ 29 ]. Briefly, the dog was taught to place its head on the headrest upon a verbal and/or gestural cue and wait in a standing position.…”

“…Despite these advantages, very little emphasis has been placed on devising behavioral methodologies to assess fundamental aspects of dogs’ hearing. A handful of studies used a behavioral approach to study dogs’ ability to localize sound [ 27 , 28 , 29 ], but, to the best of our knowledge, only Heffner [ 26 ] performed a study using a behavioral procedure to assess hearing threshold. The latter identified the hearing range of four dogs as ranging from 63 Hz to 47 kHz, determining the endpoints when sounds were only perceived if above 60 dB SPL.…”