In humans, the ability to laugh emerges as early as four months of age, with laughter being the most recognizable expression of positive emotion across cultures. Laughter, a means of communicating social information (e.g., harmless intentions), is not unique to humans however, suggesting it dates back to a shared ancestor. But along the way, humans also evolved complex speech, allowing for the use of laughter in various contexts. Selection must have favored those who could intentionally produce laughter, but also those who were able to recognize and decipher this fake laughter.
Sally D. Farley and colleagues write, “There is likely a dual pathway model for laughter production that distinguishes between spontaneous (authentic) and volitional (manipulated) laughter.”
Laughter can signal one’s affiliation, as well as encourage and maintain positive relationships. In this work, Farley’s team examined the ability to differentiate laughter directed toward two groups high in affiliation: friends and romantic partners.
Laughter stimuli was collected from archived 5-minute phone calls involving 27 individuals who called their romantic partner and a close same-sex friend. From the 54 calls, laughter segments were clipped, yielding a total of 52 laughter segments (after omitting 2 calls that had no laughter). Study 1 recruited 50 students from the mid-Atlantic region of the United States who rated the 52 segments on a scale of 1 (extremely unpleasant) to 9 (extremely pleasant). They listened to each laugh a second time in randomized order, and indicated whether they believed the laughter was directed toward a friend or romantic partner.
Participants had a better than chance accuracy for differentiating laughter between these two groups. As well, laughter directed toward romantic partners (vs. friends) was rated as less pleasant sounding. Rates of accuracy did not differ for friend and romantic laughter. Further, men and women had similar rates of accuracy. This is surprising, given women are more sensitive to nonverbal cues and tend to outperform men in these judgements.
The two most accurately identified laughs for all laughter types (i.e., female/male friend and female/male romantic partner) were selected as examples of prototypical laughs, for a total of 8 laugh segments. A total of 58 participants provided 9-point ratings for the dimensions of spontaneity (e.g., relaxed/tense, changing/monotone) and vulnerability (e.g., warm/cold, submissive/dominant).
Given the scales for each dimension were not highly correlated, the researchers analyzed them separately. Laughter directed toward friends (vs. romantic partners) was rated as louder, more masculine, dominant, slightly more mature-sounding and less breathy. Male laughter was perceived as more masculine and colder, while female laughter was perceived as louder, more natural, changing, mature, relaxed, and dominant.
Study 3 utilized 12 laugh segments (3 per condition) from a prior Farley study; these clips were different from those used in Study 2. A total of 252 individuals (125 men) recruited on the online crowdsourcing platform, Prolific, participated in this research. They listened to the 12 laugh segments one at a time and in random order, providing ratings on a 9-point scale ranging soft/loud, cold/warm, natural/forced, not breathy/breathy, submissive/dominant, relaxed/tense, masculine/feminine, and monotone/changing. Laughter audio could be played numerous times, but participants could not go back to the previous page to change a rating.
Once again, participants had a better than chance accuracy in differentiating friendship laughter from romantic laughter. As well, there was greater accuracy for friendship (vs. romantic) samples. While there were no differences between men and women in identifying friendship laughter, women had higher accuracy for identifying romantic laughter. Laughter with friends was rated as louder, warmer, more changing, natural, relaxed, breathy, and dominant, compared to laughter with romantic partners. Male laughter was perceived as more masculine, relaxed, and natural sounding, while female laughter was rated as louder, warmer, and more changing.
These studies provided some support for the researchers’ vulnerable love hypothesis, which predicted that laughter directed toward romantic partners would sound more vulnerable (e.g., submissive, warm), revealing “the vulnerable relationship status of early-stage romantic love.”
Farley and colleagues write, “Future studies should consider the variety of acoustic features of laughter such as pitch, perhaps even through artificial manipulation, to see how they affect different percepts of laughter within romantic and non-romantic contexts.”
The research, “Just Seconds of Laughter Reveals Relationship Status: Laughter with Friends Sounds More Authentic and Less Vulnerable than Laughter with Romantic Partners”, was authored by Sally D. Farley, Deborah Carson, and Susan M. Hughes.