How Does Rumination Impact Cognition? A First Mechanistic Model

Rumination is a process of uncontrolled, narrowly focused negative thinking that is often self-referential, and that is a hallmark of depression. Despite its importance, little is known about its cognitive mechanisms. Rumination can be thought of as a specific, constrained form of mind-wandering. Here, we introduce a cognitive model of rumination that we developed on the basis of our existing model of mind-wandering. The rumination model implements the hypothesis that rumination is caused by maladaptive habits of thought. These habits of thought are modeled by adjusting the number of memory chunks and their associative structure, which changes the sequence of memories that are retrieved during mind-wandering, such that during rumination the same set of negative memories is retrieved repeatedly. The implementation of habits of thought was guided by empirical data from an experience sampling study in healthy and depressed participants. On the basis of this empirically derived memory structure, our model naturally predicts the declines in cognitive task performance that are typically observed in depressed patients. This study demonstrates how we can use cognitive models to better understand the cognitive mechanisms underlying rumination and depression. Van Vugt, van der Velde, and collaborators show how cognitive architectures can implement verbal theories of psychiatric problems. They show how one theory of depressive rumination can be implemented in the ACT-R cognitive architecture by changing the contents of its simulated memory. These manipulations of memory habits lead the model to show impairments in a sustained attention task--a plausible impairment given that people who suffer from depression have concentration complaints.