Abstract
Replying to C. Andersson & D. Read Nature 511, 10.1038/nature13411 (2014)
In the accompanying Comment1, Andersson & Read challenge our results2 that group size influences cultural complexity. Using a dual-task computer game, our experiment demonstrated that an increasing group size prevents the loss of cultural traits (simple and complex), promotes their improvements and prevents cultural richness to disappear2. Among these various effects, Andersson & Read1 are questioning the finding that larger groups favour the persistence of the complex trait.
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References
Andersson, C. & Read, D. Group size and cultural complexity. Nature 511, http://dx.doi.org/10.1038/nature13411 (2014)
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Derex, M., Beugin, MP., Godelle, B. et al. Derex et al. reply. Nature 511, E2 (2014). https://doi.org/10.1038/nature13412
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DOI: https://doi.org/10.1038/nature13412
Dwight Read
The reply by Derex et al. reiterates, hence reinforces, what we stated in our critique, namely that the increase in the frequency with which complex artifacts are drawn in larger groups is a sample size effect. The sample size effect is well-known and hardly needs to be experimentally verified. What they needed to experimentally verify, but did not, is an evolutionary effect relating to complexity deriving from group size. Instead, their estimate of P = 0.80 for the probability — averaged over all group sizes through their use of a generalized linear model — of an individual drawing a simple artifact on the last step of the experiment simply shows, as we demonstrated, that individuals in the larger groups are more likely to draw a simple artifact on the last step of the experiment than individuals in groups of size 2 since P = 0.80 > 0.73, the maximum likelihood estimate of drawing a simple artifact in groups of size 2.
Further, their computation of the ?probability of getting outcomes as extreme as, or more extreme than, our observed data for each group size? is both biased by the greater likelihood of drawing a simple artifact in the larger groups and does not take into account the pattern of all groups of size > 2 having observed values exceeding the expected values. The proper way to avoid both the bias and to take into account the pattern for the larger groups is the method we used in our critique.
Finally, a recent analysis (ref. 1) of ~150,000 self-organized team projects only finds a rank correlation of ? = 0.08 between team size and success of teams, indicating that less than 1% of the variation in team success can be attributed to team size and then only with a massive data set.
Altogether, these data do not support the claim of group size as a significant driver of complexity, keeping fixed the structural organization of groups.
Dwight Read
Claes Andersson
1. Klug, M. and Bagrow, J. P. 2014. Understanding the group dynamics and success of teams. Cornell University Library Preprint Series in Social Information and Networks. arXiv:1407.2893 [cs.SI]