It is not spite or boredom (well, not only boredom). A 2021 study from animal behavior researchers at the University of Exeter found that domestic cats exhibit object-manipulation behavior — batting, pawing, and dropping items — as an extension of predatory motor patterns. When cats are understimulated or have excess prey-drive energy with nowhere to go, they redirect it onto inanimate objects. The "knock it off" behavior activates the same neural reward circuits as catching prey: swipe, register movement, investigate outcome. The falling object triggers a dopamine hit. Objects near edges are especially irresistible because cats instinctively test environmental stability — a behavior that in the wild would reveal hidden prey beneath surface cover.
Give your cat a minimum of two 10–15 minute interactive play sessions per day using wand toys or feather teasers. This drains predatory energy before it redirects to your coffee mug. Moving toys that dart and hide mimic prey movement most effectively. If the knocking behavior is constant, your cat likely needs more environmental enrichment: puzzle feeders, window perches with bird-feeder views, or a second cat.