Reasoning requires making inferences based on information gleaned from a set of relations. The relational complexity of a problem increases with the number of relations that must be considered simultaneously to make a correct inference. Previous work (Viskontas, Morrison, Holyoak, Hummel, & Knowlton, 2004) has shown that older adults have difficulty integrating multiple relations during analogical reasoning, especially when required to inhibit irrelevant information. We report two experiments that examined the ability to integrate multiple relations in younger, middle-aged, and older (...) adults performing two other reasoning tasks. These tasks systematically varied relational complexity, and required either inductive reasoning (a version of the Raven's Matrices Task) or transitive inference. Our results show that as people age they have increasing difficulty in solving problems that require them to integrate multiple relations. This difficulty may stem from a decrease in working memory capacity. (shrink)

Suddendorf & Corballis (S&C) argue that episodic memory is the most flexible and recently evolved memory system, and point to the reorganization of prefrontal cortex throughout human evolution as the neuroanatomical substrate. Their approach, however, fails to address the unique role that the hippocampus, a primitive brain region, plays in creating and recalling episodic memories, as well as future event construction.

Studies of neuropsychological patients are relevant to models of how long-term memories are stored. If amnesia is considered a binding deficit and not a difficulty in transferring information from short-term to long-term memory, it is unclear why context-free semantic learning is impaired. Also the model should account for the reverse temporal gradient seen in patients with semantic dementia.

Blair argues that fluid cognition is dissociable from general intelligence. We suggest that a more complete understanding of this dissociation requires development of specific process models of the mechanisms underlying fluid cognition. Recent evidence indicates that relational integration and inhibitory control, both dependent on prefrontal cortex, are key component processes in tasks that require fluid cognition. (Published Online April 5 2006).