The generative entrenchment of an entity is a measure of how much of the generated structure or activity of a complex system depends upon the presence or activity of that entity. It is argued that entities with higher degrees of generative entrenchment are more conservative in evolutionary changes of such systems. A variety of models of complex structures incorporating the effects of generative entrenchment are presented and we demonstrate their relevance in analyzing and explaining a variety of developmental and evolutionary (...) phenomena, both on a macroscopic developmental and evolutionary scale, and using models and strategies pioneered by Kauffman, on the more microscopic scale appropriate to the analysis of the structure and behavior of gene control networks. The resulting picture suggests that generative entrenchment acts as a powerful and constructive developmental constraint on the course of evolutionary processes. Since virtually any system exhibits varying degrees of generative entrenchment among its parts and activities, these studies and results have in addition broad potential application for the analysis of generative structures in other areas. (shrink)
Andrews et al. argue for adaptationism in cognitive research. However, the problem of evolvability brings into question the number of genes required for the evolution of cognitive mechanisms. Are there enough? Also, greater consideration should be given to alternative vicarious selection processes, which may produce cognitive mechanisms. Finally, identifying constraints with optimality arguments is more difficult than the authors think.
It is widely believed that women who live together or who are close friends synchronize their menstrual cycles. We reexamined this phenomenon in two ways. First, we collected data on menstrual cycles from 186 Chinese women living in dorms for over a year. We found that women living in groups did not synchronize their cycles. Second, we reviewed the first study reporting menstrual synchrony. We found that group synchrony in that study was at the level of chance. We then show (...) that cycle variability produces convergences and subsequent divergences of cycle onsets and may explain perceptions of synchrony. (shrink)
Because of the complexity of human emotional responses, invariants must be sought not in the responses themselves, but in their generating mechanisms. Lindquist et al. show that functional locationism is a theoretical dead end; their proposed mechanistic framework is a first step toward better models of emotional behavior. We caution, however, that emotions may still be quasi-natural perceptual types.
Webb has articulated a clear, multi-dimensional framework for discussing simulation models and modelling strategies. This framework will likely co-evolve with modelling. As such, it will be important to continue to clarify these dimensions and perhaps add to them. I discuss the dimension of generality and suggest that a dimension of integrativeness may also be needed.
Research over the past 15 years indicates, contrary to earlier results, that women do not synchronize their menstrual cycles. If women do not synchronize their cycles, this implies there is no mechanism for synchronizing cycles. Since a pheromone mechanism of synchronization is the only plausible mechanism that has been proposed, it follows that that there are no pheromones that modulate the length of menstrual cycles. To test this hypothesis, eight studies were reviewed that reported pheromone effects on menstrual cycles, other (...) behavior, or physiological correlates in women. The prediction was that serious problems would be found in each of these studies. As predicted, serious problems were found in all eight studies. Taken together, these results cast doubt on the existence of pheromones that modulate the length of menstrual cycles. (shrink)