Analysis of human-oriented facial signals of the domestic dog using eye tracker technology

Understanding canine facial signals is crucial for responsible dog ownership and animal welfare, yet how humans visually process these signals in breeds with extreme morphology remains under-researched.

This study examined visual attention patterns using eye-tracking when humans viewed brachycephalic versus normocephalic dog faces. Forty-four undergraduate students viewed photographs of Boston Terriers (brachycephalic) and Jack Russell Terriers (normocephalic) depicting four emotional contexts: positive (Called by Name, Play) and negative (Separation, Stranger Threat). Eye-tracking measured fixation duration, number of visits, and saccades across eight facial regions (eyes, ears, cheeks, forehead, snout). Participants also self-reported which regions they believed they attended to most.

Brachycephalic dogs elicited 45-46% more visual attention across all frequency- based measures: longer total fixation duration (M = 1103.62 ms, SD = 1364.14 vs. M = 760.08 ms, SD = 1165.99; p < 0.001), more fixations, and more visits. Critically, average fixation duration did not differ between breeds, indicating intensive sampling through repeated revisits rather than deeper processing per fixation. Regional analyses using linear mixed-effects models revealed the strongest effects for the ears (Hedges' g = 0.69-1.59), followed by the eyes, forehead, and snout. The right eye was the only region showing greater attention to normocephalic dogs. Substantial discrepancies emerged between self-reported and objectively measured attention: participants underestimated eye fixations while overestimating snout attention.

These findings suggest that extreme brachycephaly is associated with increased visual processing demands, potentially requiring more frequent sampling to interpret facial signals. This may impair signal readability with important implications for animal welfare, veterinary practice, and human-dog communication.