Why do cats like to push stuff over edges and then curiously watch the fallen object? I suggest that they are play-hunting, and are testing the ‘prey’ for liveness & playing-dead, similarly to tossing or poking it with claws.
Good cat toys simulate hunting. The play = hunting paradigm may also explains why cats love to push things over edges.
The question of why cats famously knock objects over is unresearched as far as I know: it’s mysterious, because they often push over the same object as before, so it doesn’t seem to be novel or learning, one would think; but writing it off as ‘boredom’ or ‘randomness’ is not an answer, because there are so many other ways to modify an environment, and this provides no explanation for why knocking-over specific objects is so consistently-chosen behavior.
Why? Because pushing tests the possibility of deceptive prey playing-dead! To explain it, one might surmise that ‘knocking over’ is an explorative hunting behavior, testing prey for information about whether it’s merely playing dead.
This explains why the objects tend to be prey-like in size (with large or shattering objects being frightening), sometimes semi-mobile, they watch the results so intently despite the (to us) predictability, and persevere in it but decreasingly so.
Q-tips have many uses. Like cleaning earwax from an ear, and then letting a cat nom it, and then, oft as not, knock it off the table or desk—as indeed cats are notorious for doing with any small object in reach. But while watching my cat play with Q-tips (used or not), I’ve noticed that no matter how many times I put down a Q-tip on my desk after he’d knocked it off, he was still interested in knocking it off & then watching it intently—as if he had suddenly begun to doubt the law of gravity or suffered amnesia about the countless prior instances, and needed to test it again and again.
Pushing Perserverance
One day, curious whether he even could get bored of knocking the q-tip off my desk, I experimented with replacing the q-tip to see how many times he’d bat it off before quitting: it took 15 times before he disdained it & left to do other things. What I noticed watching him was that he started by gingerly, delicately prodding it (as if it might scald or bite him) repeatedly with his claws off the table, eventually escalating to batting it off the moment I put it down. He was not too interested in the knocking-off part nor the falling part, but he would instead carefully watch the fallen q-tip lay there on the floor as it did nothing each time. And his intensity didn’t slacken until the end, when he abruptly gave up and stalked away.
Poking Prey
Eventually, I realized: this was not random destruction nor boredom. Rather, this sort of ‘testing’ was the same way he interacted with live prey!
He would capture and bring them in to play with them; and when they stopped moving, he would gently prod them with claws to provoke a reaction, escalating if they didn’t react, and with an apparently dead animal like a vole or mouse, might scoop it up or fling it around. He was testing them, trying to see whether they were still alive and could be played with, and they might be refusing to move or playing dead, and so a single test is inadequate—one must poke them repeatedly, watching for any sign of life.
Pushing = Play
And that’s the same behavior of a cat knocking things off an edge to see what happens. It is not that they truly think that an egg or a q-tip or a smartphone might be prey, any more than they think that the cat toy they are chasing is truly living prey animal, but it taps into the same hunting drives & play behavior.
If the object is too large, or too small, then it doesn’t seem prey-like: it’s striking that while cats sometimes knock over large objects like lamps or dishes (especially their own food dishes), they seem as surprised & frightened as anyone else by the crash. It’s the much smaller, more rat/mouse-sized objects (like eggs), that they tend to deliberately knock-over. And since cats need to play regularly, the knocking-over habit is never permanently satisfied & never goes away (but fades away with age with the hunting & play drives).
We can contrast this with similar behavior in humans, which does go away: infants gleefully knock over glasses or dishes to watch them fall & shatter, and it is highly novel to them because they don’t understand the world at all; but as they get older, ‘push that glass off the table’ becomes boring, and teenagers must thrill themselves with more advanced forms of destruction (like jumping off roofs or posting on social media).
Predictions
This can be tested in a similar way as et al 2002 tested their toy = hunting hypothesis: knocking-over should maximize information about prey-objects (there is no need to test if one already knows the answer), and should be caused by hunting drive, in a way clearly distinguishable from regular boredom or random destruction (which would be unaffected by most of these traits or changes).
So:
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Hunting Correlates: anything that increases/decreases hunting should increase/decrease the rates & perseveration of knocking-over behavior, such as time-of-day or hunger or aging or hunting in general (between-individual and between-species) correlating with knocking-over;
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Prey-like Objects: cats should prefer to knock over more prey-like objects (such as correctly-sized objects which are not too large or too small; correctly-weighted objects, which are not bizarrely heavy or lightweight; or fur-textured objects more than artificial-textured objects), and also prefer more novel specific objects, and more novel kinds of objects (to learn if they are prey-like);
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Unnatural is Surprising: cases of cats being frightened or scared by something they deliberately knocked-over should correspond to ‘unnatural’ outcomes.
Prey would not trigger chain-reactions of falling furniture, nor would a mouse hitting the floor splatter the way an egg does (even if an egg is otherwise the right size & density, and wobbles intriguingly)
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Unexpected is Interesting: objects which are familiar but unexpected in location may also be tempting.1
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Knocking Only Dead Prey: cats should knock-over real prey only if the prey had stopped moving (and they should not knock-over live prey which is still clearly active);
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Knocking More Realistic Prey: making knocked-over objects resemble prey playing dead ought to greatly increase knocking-over rates & perseveration (eg. if objects squeaked or rustled when pushed; or if they were ‘self-righting’ like some toys are; or if objects were rigged to occasionally wiggle briefly after a shock, like an animal struggling to maintain stillness after being hurt badly).
This effect should be especially strong in indoor-only cats which haven’t been to live prey at all: they should engage in little knocking-over before exposure to live prey playing-dead, and then do much more afterwards once they’ve learned ‘playing dead’ is a thing.
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Uncertainty reduction: One could manipulate time delays to see if cats adjust their observations to be informative: if a knocked-over object wiggles with high probability but only after a long delay, does a cat observe more patiently? If it has a short delay but the probability is lower, do they prefer to instead knock-over more frequently while observing only briefly?
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Uses
If knocking-over turns out to be play-hunting as well, this would suggest a way to cope with destructive knocking-over behavior: offer toys designed to be knocked-over & act like playing-dead prey2
It would also suggest that if it’s taken us this long to figure out the reason for such a commonly-observed cat behavior, we are bad at understanding cat boredom, and that since we have underestimated their boredom levels, we should look for other misinterpreted play-hunting behavior.
Cat pondering Hume’s problem of induction. (Experiment in DALL·E 3 comic generation.)
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One might experiment with objects which unexpectedly pop up, but such motion, as much as it might intrigue a cat, would lead to ambiguous interpretations.↩︎
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This could tie back into the general toys-should-simulate-hunts-better point—perhaps knocking-over toys could intermittently dispense treats, like on alternating days so a cat cannot simply learn whether a toy does or does not dispense a treat, but must each day knock them over and observe it to learn whether it’s a “treat-day”?↩︎