6 The Role of Working Memory in Higher - Level Cognition

The idea that short-term memory is an important component of intelligence is not new. For example, over a century ago James (1890) wrote, "All the intellectual value for us of a state of mind depends on our after memory ofit. Only then is it combined in a system and knowingly made to contribute to a result. Only then does it count for us." Around the same time, Binet (1905) included a test of short-term memory in a test battery designed to identify learning disabled children in the Paris school system. And more recently, short-term memory has been conceptualized as a fundamental component of human cognition. For example, Miller (1956) famously proposed that the capacity of short-term memory is limited to 7 ± 2 bits of information. Later, Atkinson and Shiffrin (1968) incorporated this idea of a central bottleneck in information processing into their "modal" model of memory. Nevertheless, the extent to which short-term memory plays an impor­ tant role in higher-level cognition intelligence manifested in complex cognitive activities like reasoning and learning has been a topic of con­ siderable debate in cognitive psychology. Consider, for example, the results of a series of experiments by Baddeley and Hitch (1974). The surprising finding in these experiments was that a secondary task designed to tax short-term memory had little or no effect on a variety of reasoning, com­ prehension, and memory primary tasks. In one such experiment, subjects performed a task in which the goal was to verify sentences purporting to describe the relationship between two letters (e.g., A precedes B BA) while maintaining a memory load. The secondary task had little effect on subjects' success in the task a finding logically inconsistent with the assumption of short-term memory as a central bottleneck in information processing. Baddeley and Hitch ( 197 4) therefore proposed that short-term memory­ the passive storage of information is but one part of a memory system