Read the following passage and fill in each blank with ONE suitable word.

Humans start developing a sense of humour as early as six weeks old, when babies begin to laugh and smile in (61)………… to stimuli. Laughter is universal across all human cultures and even exists in some forms in rats, chimps, and bonobos. Like other human emotions and expressions, laughter and humour provide psychological scientists (62)…………resources for studying human psychology, ranging (63)…………the development of language to the neuroscience of social perception.

Theories focusing on the evolution of laughter point to it as an important adaptation for social communication. (64) …………, for example, the recorded laughter in TV comedy shows. Back in 1950, US sound engineer Charley Douglass hated dealing with the unpredictable laughter of live audiences, so started recording his own ‘laugh tracks’. These were intended to help people at home feel (65)…………they were in a social situation, such as a crowded theatre. Douglass even recorded various types of laughter, as well as mixtures of laughter from men, women, and children. In doing so, he picked (66)…………on a quality of laughter that is now interesting researchers: a simple 'haha' communicates a remarkable amount of socially relevant information.

In one study (67)…………in 2016, samples of laughter from pairs of English-

speaking students were recorded at the University of California, Santa Cruz. A team (68) …………up of more than 30 psychological scientists, anthropologists, and biologists then played these recordings to listeners from 24 diverse societies, from indigenous tribes in New Guinea to city-dwellers in India and Europe. Participants were asked (69)…………they thought the people laughing were friends or strangers. (70)…………    average, the results were remarkably consistent: worldwide, people’s guesses were correct approximately 60% of the time.

(adapted from IELTS15 Academic Student’s Book with Answers’)

Humans start developing a sense of humour as early as six weeks old, when babies begin to laugh and smile in (61)………… to stimuli