“Oh, no”, I found myself thinking about 20 minutes ago, “Adam Kendon was right and my family is wrong”. And all because a dog wagged his tail and I waved at it.

dag wagging tail
Nice to meet you too, dog. (source)

I recently formulated some hypotheses about the perception of waving on behalf of, or inspired by, my son Rik:

H0: Waving is limited to humans and contexts such as greeting or saying goodbye where waving is to be expected
H1: Anything can and will be seen as waving as long as the movement characteristics are right (e.g. repeated small side-to-side arched movement, from rotation around fixed point)
H1b: Anything can wave, but only if it has something resembling hands

Actually Rik only proposed “Snoopy has hands, thus he can say ‘bye’ with them”, which I turned around into the negative form of “If it [Snoopy] does not have hands it cannot wave [say ‘bye’ with them]”.

dag wagging tail
Anything can be given hands (source).

At first sight the null-hypothesis seems ridiculous. Anyone in their right mind will have countless experiences concerning waving dolls, snowmen, and other assorted electrical toys. It is easy to see the weirdest cartoon characters (think SpongeBob and friends) waving in all sorts of ways to each other or even at the viewer. But I will posit here as an additional explanation of H0 that such waving is caused by anthropomorphisation. We pretend these toys and cartoon characters are real humans. Thus, we play along with their makers who already suggest strongly that we do so, by labeling their products as toys or cartoons. We are supposed to see waving and we go along with it.

I think it is important to separate anthropomorphisation from other factors in wave perception. I suppose H1b may in fact be a special version of the anthropomorphisation position. Perhaps if we are supposed to see hands, we are also supposed to see waving. Snoopy has something I am supposed to see hands, therefore I am supposed to accept his waving. The question rises if it is possible for some non-human object to have ‘hands’ but not be the subject of anthropomorphisation. Or is in fact the projection of ‘hands’ an immediate case of anthropomorphisation. I will leave this matter open for now.

It is at least clear that there are also cases where neither anthropomorphisation is at work, nor are their hands, yet still a ‘waving movement’ is present. We may think of waving grass, trees waving in the wind, animals shaking their heads or limbs, or mechanical devices other than toys or robots. Will the waving movement in such cases cause us to be (temporarily) fooled and see waving. Can we create the illusion of waving without resorting to hands or the suggestion of human characteristics? That is what we need in order to support H1 that anything can be seen as waving.

Well, I still have to design a nice experiment (or maybe someone else can) to get to the bottom of this, but I do have a case study now that I would like to share with you:

I was driving in my car and another car was driving about 20 meters in front of me. I suddenly spotted movement in the backseat of the car, which I recognized as waving (I was guessing that a couple of kids were waving through the rear window) and I waved back. The car slowed and as I came closer I noticed that I had waved to the wagging tail of a big german shepherd dog. The dog was moving around in the trunk of the stationwagon. I will ask you: was I first speculating there were kids before I saw them ‘waving’? Or did I first see the illusion of ‘waving’ and then projected a couple of kids to fit the illusion? I think the latter is true and H1 is supported, but the question remains to what extent the rear window context sparked the waving illusion.

waving man in car
Do you always spot wavers from cars?

I sometimes see kids waving from cars at me and I always like to wave back. It is probably safe to say I am very sensitive to waving from rear windows of cars. Other people may be totally insensitive to it, even to the point that they wouldn’t see it if the kids were frantically waving at them from a car only three feet away. I hope the driver of the car in front of me was one of them.