Associations between Domestic-Dog Morphology and Behaviour Scores in the Dog Mentality Assessment

Abstract

The domestic dog shows a wide range of morphologies, that humans have selected for in the process of creating unique breeds. Recent studies have revealed correlations between changes in morphology and behaviour as reported by owners. For example, as height and weight decrease, many undesirable behaviours (non-social fear, hyperactivity and attention seeking) become more apparent. The current study aimed to explore more of these correlations, but this time used reports from trained observers. Phenotypic measurements were recorded from a range of common dog breeds (n = 45) and included cephalic index (CI: the ratio of skull width to skull length), bodyweight, height and sex. These data were then correlated with results from the Dog Mentality Assessment (DMA), which involves trained observers scoring a dog’s reaction to stimuli presented over 10 standardised subtests. Each subtest is designed to evoke a behavioural response. Backward elimination and weighted step-wise regression revealed that shorter dogs demonstrated more aggressive tendencies, reacting defensively toward both assistants dressed as ghosts (p = 0.045), and to a dummy (p = 0.008). Taller dogs were more affectionate when greeting and being handled by humans (p = 0.007, p = <0.001, respectively). Taller dogs were also more cooperative (p = <0.001), and playful (p = 0.001) with humans than shorter dogs. Heavier dogs were more inquisitive toward a dummy (p = 0.011), to the source of a metallic noise (p = 0.010) and to an assistant (p = 0.003). Heavier dogs were also more attentive to the ghosts (p = 0.013). In comparison, lighter dogs were cautious of a dummy (p = <0.001) and fearful of the sound of a gunshot (p = <0.001). Lighter dogs were also cautious of, and demonstrated prolonged fearfulness toward, the source of metallic noise (p = <0.001, p = <0.034, respectively). With a far larger sample and the advantage of third-party reporting (which overcomes potential owner bias), the current findings build on previous studies in this field, further supporting covariance between morphology and behaviour.

Inadequate socialisation, inactivity, and urban living environment are associated with social fearfulness in pet dogs

“…We discovered that small dogs were more likely to show fear of dogs and strangers than large dogs. This result agrees with previous studies showing that fear of dogs and strangers decreases as the height of the dogs increases 39 , and that larger dogs are bolder in general 38,40,41 . Small sized dogs may feel more threatened by people and larger dogs due to the larger relative size difference and hence be more fearful.…”

“…Second, we hypothesised that female dogs would be more fearful than male dogs 33,36,37,52,53 . Third, we hypothesised that large dogs would differ from small dogs in their behaviour [38][39][40][41] . Fourth, contrast between early weaning (weaned <7 weeks of age) and normal weaning age (7-8 weeks of age) as well as contrast between normal weaning age and late weaning age…”

Significant Neuroanatomical Variation Among Domestic Dog Breeds

“…In comparative animal cognition research, total brain size is often used as a gross index of cognitive capacity. Several previous studies have investigated the relationship between dog body size and cognition or behavior, with apparently contradictory results (Helton and Helton, 2010;Stone et al, 2016;cf. Broadway et al, 2017).…”

“…Cephalic index is defined as the ratio of skull width to skull length ϫ 100. For many scans in our database, the exterior of the skull was not visible, but a large database of skull measurements is publicly available (Stone et al, 2016). We computed male and female average cephalic (Table continues) indices separately for each breed and used these sex-specific, breedaverage measures in our analyses.…”

“…Dogs from mixed/unknown breeds were excluded from analyses that used breed group as an independent variable. Cephalic indices are sex-and breed-specific averages from a large public database (Stone et al, 2016). ND, No data.…”