What Does a Dog’s Tail Say?

More Than You Think—Even About Brain Activity

A new study reveals that the direction of a dog’s tail wag may reflect what’s going on in its brain and emotional state.

Researchers used spatial data from motion sensors placed on the dog’s body (especially the tip of the tail), combined with machine learning techniques to automatically classify tail movements: right, left, or no wag. The SVM model reached an impressive accuracy of 80–98%.

But the emotional insights are the real kicker:

• Wags to the right were more often linked to positive emotions—like excitement or interest.

• Wags to the left were more often tied to negative emotions—like anxiety or stress.

This matches what we know from neurobiology:

• The right hemisphere (which controls the left side of the body) is more active in processing threats or unpleasant stimuli.

• The left hemisphere (controlling the right side) activates more in response to positive or familiar stimuli.

These findings confirm previous research but now with more precise and non-invasive technology.

They also highlight how closely dog emotions and behavior are tied to brain lateralization—how the two brain hemispheres process different kinds of information.

Tail wags aren’t just cute—they’re neuroscience in motion.

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Greene Mex, C. E., Aguileta Güémez, A. A., Rios-Martinez, J. A., & Aguilar Vera, R. A. (2023). Dog tail wag classification using deep cameras and support vector machine. Abstraction & Application, 49, 123–135.