Correlated Interaction and Group Selection

Okasha ([2005]) argues that correlated interactions are necessary for group selection. His argument turns on a particular procedure for measuring the strength of selection, and employs a restricted conception of correlated interaction. It is here shown that the procedure in question is unreliable, and that while related procedures are reliable in special contexts, they do not require correlated interactions for group selection to occur. It is also shown that none of these procedures, all of which employ partial regression methods, are reliable when correlated interactions of a specific kind arise, and it is argued that such correlated interactions will likely be ubiquitous in natural populations.