Unobtrusive observation was used to compare time in the store and load size of lone and group shoppers. Consistent with social facilitation theory, groups spent more time in the store and purchased larger loads than did lone individuals. The larger loads of group shoppers held up with shopping time controlled. Women and older people spent more time in the store and bought larger loads than did men and younger people.
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Sommer et al. (1992) studied this question.
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