Sleight-of-hand magic trick only fools monkeys with opposable thumbs

An illusion involving a hidden thumb confounds capuchin and squirrel monkeys for the same reason it does humans — it misdirects expected outcomes of actions they can carry out. However, marmosets have five equidistant digits, and were rarely fooled by the magician. The research adds to evidence that animals struggle to predict movements outside of their own ‘biomechanical ability’.

Source: ScienceDaily.com