Chiral Wag Hilarometry

It seems (first link) that the information conveyed by a dog's wagging tail is chirally differentiated - that is to say, a wag to the left means something different from a wag to the right.

Specifically, if Fido's tail is moving mostly to his left, then he's more anxious than happy. (The report doesn't say whether there's a minority of left-handed dogs who wag anxiously to the right).

Now, back in 1967, Desmond Morris (The Naked Ape, pp.102-3) postulated that laughter is a combination of expressions of anxiety with those of relief - and experience tends to confirm this as a useful theory.

Meanwhile, even further back, Max Eastman observed that "Dogs laugh, but they laugh with their tails".

Clearly, then, a laughing dog is one whose tail moves through many degrees of arc on *both* sides of a tangent to its spine at some point near its pelvis.

A hardware device looped around the tail might cause some discomfort, so an array of cameras with image-analysis software would provide the most humane way to gather the basic data.

The metric would be defined at any given point in time in relation to the previous two inflection points on a notional graph of the movement of the dog's tail. At any given inflection point, a tangent to the tail at a given distance from the dog's pelvis will be at a certain angle to the tangent to its spine mentioned above. The metric would have the value of the smaller of those two angles, unless the tail were actually at rest, in which case the value of the metric would be zero.

The usefulness of this metric, which I have not yet named, will be most apparent to those stand-up comedians who specialize in making dogs laugh. I read a while ago that the turnover of the North American pet products industry is the same size as the entire GDP of the state of South Australia, so, if such comedians do not *yet* exist it is, surely, only a matter of time.