20 December 2013

Dog Tail Wagging

Welcome back. If it’s not icy, below zero or raining hard, I take a brisk walk along the same route within about 30 minutes of the same time every afternoon.

I don’t pass many houses, but there’s one set back from the road, where on weekdays, barking starts as I approach and continues until I’m far beyond the house. Since I neither whistle, sing nor walk loudly, I presume the dog is at a window, awaiting the homeowner’s return.

Three weeks ago, the dog attacked me, sort of. I was walking by the house in my usual manner, when an average size, mature, black Labrador came running up to me, growling. My only defense was to take the Frisbee from its mouth and toss it. That of course led to petting and repeated tosses and retrievals. I had no choice; it kept growling.

The dog was wagging its tail, but at the time, I didn’t realize that I should be heeding the wag direction. It was only after I saw a recent study on dogs recognizing other dogs’ tail wag direction that I discovered the earlier research. I can’t believe those findings didn’t make the headlines. Or is it that we had cats, and I wasn’t looking for dog insight?

Earlier Tail-Wagging Study

Expanding the research on behaviors associated with specialization of the left and right sides of the brain, collaborators from Italy’s Bari and Trieste universities examined the lack of symmetry in dog tail movement, i.e., wagging.

In controlled experiments, they exposed 30 mixed breed, pet dogs, 1 to 6 years old, half male-half female, to four visual stimuli: the dog's owner; an unknown person; a dominant unfamiliar dog; and a cat.

This was done by placing the dogs in a confined space, with essentially an opaque window that was opened for 60 seconds for the dogs to see the different stimuli. The absence of any visual stimulus was also recorded.

Tail movements associated with each stimulus were analyzed systematically from video recordings. Data for male and female dogs were combined since there were no significant differences.

A dog’s wagging tail. Note the negative,
withdrawal direction (right-brain activated).
(Photo by www.rachelphilipson.com)
The investigators found a significant bias in tail wagging to the right (left brain activated) when the dogs saw their owner (high amplitude wagging), the unknown person (medium amplitude) and the cat (very low amplitude). In contrast, there was a significant bias in tail wagging to the left (right brain activated) when the dogs saw the unfamiliar dog or no stimulus.

Recent Tail-Wagging Study

I won’t go into detail about the recent study conducted by most of the same investigators, now at Bari and Trento universities. The findings reinforce the earlier study and are equally fascinating.

In short, dogs watching video images of other dogs had higher cardiac activity and more anxious behavior when they saw left- rather than right-biased tail wagging. The dogs recognized and responded differently to other dogs’ positive approach emotion (wagging right) and negative withdrawal emotion (wagging left).
Monitoring wag direction with these
dogs is going to be difficult.(Photo by

Wrap Up

The researchers conclude that their findings link brain asymmetry and social behavior and may be of value to both the theory and practice of canine welfare. I’ll bounce that off my niece, the veterinarian; our letter carrier never leaves the car.

Before we take this too far, however, I think the findings must be tested with dogs from other countries. Perhaps dogs raised in Italy are merely expressing their version of the hand and finger gestures so common in Italian conversation.

Thanks for stopping by.


- Study of dogs recognizing other dogs’ tail wagging in Current Biology and article on the study on Science Daily:
- Earlier study (2007) of dogs’ asymmetric tail wagging responses in Current Biology:
- Articles on Italian hand gestures:

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