Fig. 1
From: Bonobos tend to behave optimistically after hearing laughter
Experimental set-up. The experiment began with the bonobo (b) sitting close to the initiator button (a). Pressing the button prompted a new trial, in which the primary experimenter (d) presented a box (c) and the subject either approached (GO) or pressed the button to skip to the next trial (NO-GO). Image illustrated by Luke Townrow (CC BY).
