In what must have been some of the most enjoyable experiments ever, scientists studied nearly 50 dogs of all shapes and sizes to assess which paw each pooch prefers – something believed to be a predictor of behavioral issues.
Despite its amusing premise, the international team of researchers led by the University of Bari Aldo Moro (UNIBA) in Italy developed an entirely new methodology to reliably determine a dog's “left-handed” or “right-handed” preference.
Earlier studies, like this one in 2019, found that individual dogs expressed a preference for a left paw or right paw, while some showed no favoritism. However, these formative studies generally employed a single test.
It may seem trivial, but paw preference is of particular interest to scientists, as it's seen as a kind of window into brain lateralization (asymmetry). Essentially, it reveals whether one hemisphere of the brain takes the lead in processing information or controlling behavior.
"When we talk about laterality, we talk about two aspects," Marcello Siniscalchi, a veterinary physiologist at UNIBA, told Science. "The first is direction: You can be either left-handed, right-handed, or ambilateral. But there is also another important aspect, which is strength: How much are you right-handed, or how much are you left-handed? This aspect is very important because there is evidence that both direction and strength affect physiology, immune response, and behavior in dogs."
A 2018 study found that strong paw preference (either left or right) was associated with greater emotional stability, confidence, and resilience, compared with rescue animals with no dominant side.
Meanwhile, dogs with weak or inconsistent preferences have been linked to more anxiety-like traits, such as fearfulness, reactivity, and noise sensitivity.
In this latest study, the team developed an entirely new way of testing for paw dominance, which they called the "Doginburgh Inventory" – a canine version of the human Edinburgh Handedness Inventory.
The researchers noted that previous research had largely relied on a single test, which they believed couldn't assess paw dominance in a meaningful way.
After all, most of us (an estimated 85 to 90%) have a dominant right hand but will use the other for specific tasks.
The team created a composite score across four activities, recruiting 43 dogs to take part. Two tests focused on manipulation – using a paw to interact with an object – and two looked at movement.
The classic Kong toy test was part of the four experiments, but the team expanded the "manipulation" side of the assessment with a task requiring the dogs to use their paws to get a treat from beneath furniture.
For the movement tests, the researchers observed which paw the dogs used when walking down stairs and then when stepping off a raised surface at home or on a walk.
Instead of assessing for left/right/no preference, the scientists created five categories – strong left, weak left, ambilateral (canine ambidextrous), weak right and strong right. The nuance is important because a dog that leads with its left paw in 55% of tasks is probably not behaving the same way as one that uses that paw 95% of the time.
The researchers found that roughly 80% of the dog participants showed consistent paw preference. Around a third had a strong preference, nearly half had a weaker one, and about one in five were ambilateral.
But unlike humans, the dogs had no significant bias toward left or right as a group. And while the studied cohort slightly favored their left paws, this was more prevalent among males. What this means is unclear, but it's one of many avenues to explore in the future.
"We want to study the effects of age and dog breed on paw preference," Siniscalchi told Science. "One of our colleagues also recently reported a mirroring effect between a dog’s paw preference and its owner’s handedness. We want to see if there is a direct correlation between the doginburgh inventory score of a dog and the Edinburgh inventory score of the caregiver, which could improve understanding of dog cognition and potentially improve training."
While the study has its obvious limitations – including the relatively small study size – the methodology provides a more thorough way to measure paw preference as it then relates to behavior.
"Developing a comprehensive paw preference inventory provides a promising tool for obtaining more precise and robust data that allow reliable comparisons across species," they noted in the paper.
"A key advantage of the ‘Doginburgh Inventory’ lies in its classification of subjects into five distinct motor laterality categories (strong left, weak left, ambilateral, weak right and strong right), as opposed to the conventional three (left, right and ambilateral) reported in the literature to date," they conclude.
"This finer categorization allows for a more detailed investigation of how motor laterality modulates physiological and cognitive processes."
The study was published in the journal Royal Society of Open Science.
Source: University of Bari Aldo Moro via Scimex
Fact-checked by Mike McRae
