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Stable social groups foster conformity and among-group differences

Citation

Michelangeli, Marcus; Munson, Amelia; Sih, Andrew (2021), Stable social groups foster conformity and among-group differences, Dryad, Dataset, https://doi.org/10.25338/B84W7B

Abstract

The social niche hypothesis theorizes that repeated social interactions between group members is an important mechanism for generating consistent individual differences in behaviour. However, such frequent interactions also have the potential to mask or suppress behavioural differences if individuals conform towards a group behavioural norm (i.e. the social conformity) by either synchronizing their behaviour or shifting their behaviour towards that of influential group members. Both of these predictions hinge on the notion that social feedback among group members plays a key role in modulating consistent behavioural variation, thus in the absence of such feedback, it could be expected that such consistent variation will be reduced. Here, we investigated how a one-month housing with a stable social group, as opposed to being socially isolated, affected consistent individual differences in the shoaling tendencies of stickleback (Gasterosteus aceluteus). Specifically, we repeatedly tested the tendency of individual sticklebacks to shoal with conspecifics before and after their social experience. In support of the social conformity hypothesis, we observed a four-fold increase in among-group differences, but no change in among-individual differences, in the shoaling tendencies of sticklebacks housed in groups. A post-hoc analysis revealed that the increase in among-group differences may have been driven by the most ‘social’ pre-treatment group member. Conversely, fish that were housed in isolation, expressed a notable, albeit non-significant, decrease in individual shoaling variation and repeatability. This decrease in shoaling variation corresponded with an increase in the average shoaling tendencies of solitary fish post-treatment, suggesting that solitary fish converged towards a similarly high level of shoaling tendencies post-treatment. For both treatment groups, however, we found among-individual positive correlations in pre- and post-treatment shoaling tendencies, suggesting that individuals may inherently differ in their shoaling tendencies, but that the social environment plays an important role in mediating the expression of these differences.

Methods

Data refers to behavioural observations recorded from social tendency assays. Specifically, sticklebacks were placed into an arena containing two 'social' zones - one social zone contained a large shoal of fish (10 fish in total) and the other social zone contained a small shoal of fish (2 fish in total). The trials ran for 10 mins and during this time we recorded the duration of time the focal fish spent in each social zone, how much time they spent outside of both zones, and a range of other activity metrics (see README file for column info)

Each focal fish was put through this assay twice, both before and after experiencing a social treatment. For the social treatment, fish were either housed in groups of 10 or housed in isolation. 

Usage Notes

See attached README file for column info