Laughter Triggers Exploratory Behavior in Bonobos
Bonobos spontaneously approach uncertain objects when hearing laughter – a phenomenon demonstrating emotional contagion in our primate cousins, according to new research published in Scientific Reports.
Experimental Design
Researchers from Indiana University Bloomington (Sasha Winkler, Erica Cartmill et al.) studied four bonobos at Iowa's Ape Cognition and Conservation Initiative:
Mali (14-year-old female)
Teco (12-year-old male)
Kanzi (41-year-old male)
Nyota (24-year-old male)
The primates were trained to:
Recognize a black box (always containing food reward)
Reject a white box (always empty) via button press
Investigate ambiguous gray boxes (light/medium/dark gray; 50% food reward probability)
Critical trials presented gray boxes while playing either:
Bonobo laughter recordings (7m28s)
Control environmental wind sounds
Key Findings
Clear choices:
93% approached black boxes
Only 1% approached white boxes
Gray box preference:
Darker boxes > lighter boxes
Laughter effect:
3.4× higher probability of approaching gray boxes during laughter vs. wind sounds
Evolutionary Significance
Bonobo laughter – acoustically similar to human laughter during play – appears to:
Trigger emotional resonance (shared positive affect)
Reduce caution toward ambiguous stimuli
Functionally promote exploration/social bonding
"Laughter likely evolved to prevent playful interactions from being misinterpreted as aggression," the authors note, adding that this emotional contagion mechanism may underpin primate empathy.
Research Limitations & Future Directions
While constrained by small sample size, this study opens new avenues for investigating:
Laughter's role in primate social evolution
Cross-species emotional contagion mechanisms
Neurobiological foundations of empathy in hominids