Visual perception in domestic dogs (Canis familiaris): global or local precedence of stimulus encoding

A global or local precedence in the visual perception of hierarchical stimuli has been found in humans and other animals; this study aimed to investigate if it also exists in domestic dogs. Family dogs (N = 8) were trained to discriminate between two bi-dimensional compound forms (S+ and S-) differing at both their global and local level (GL phase). Afterwards (Test phase), the dogs’ global-local encoding precedence was assessed, presenting one stimulus with the same global shape and one with the same local shapes as that reinforced in GL. In the last phase (L) dogs were trained to discriminate between stimuli differing only for the local shapes. In GL the number of trials needed to reach the learning criterion was 252±143 (mean±SD) and latency (time for choosing the stimulus) was 4.2±5.0 s (mean±SD). In the Test phase dogs chose the stimulus featuring the previously learned global shape more often than the one featuring the local shape (p=0.017; SE=7.13). In L dogs achieved the learning criterion in an average of 130±67 trials, which were fewer than those needed in GL (p=0.018; SE=5.90). Dogs showed a global precedence in the visual processing of hierarchical stimuli, as seen in humans. L phase demonstrated that dogs could perceive local features. The faster acquisition of L might have been due to a previous reinforcement of the local shape during GL.