Sound Localization Ability in Dogs

SIMPLE SUMMARY: An animal’s ability to localize the source of a sound on the horizontal plane is commonly measured by the minimum audible angle (MAA), i.e., the minimum angular distance between two possible sources at which an animal is still able to identify which of the two produced a sound. Only two studies explored this parameter in dogs, and both were characterized by relevant limitations: a very small sample size, and reliance on a method of assessment that might have not produced reliable results. To overcome the latter limit, we used a staircase method, whereby the dog’s rough threshold was quickly reached, and then several tests were performed around the actual perceptual limit of the dog, allowing for greater precision in estimation of the actual threshold. Moreover, the assessment lasted until the dog’s performance showed a clear stabilization. Ten dogs completed the experiment, testing angles between 60° and 1°. Their MAA ranged between 1.3° and 13.2°, with an average of 7.6°. Dogs also showed an improvement in performance across the procedure. The results show that the staircase method is feasible and reliable for assessing sound-localization sensitivity in dogs. They also reveal that the MAA of dogs is more variable than previously reported, potentially reaching values lower than 2°. Larger-scale studies should be performed to explore if and how factors such as ear and head shape or age influence sound localization abilities 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.