Intelligence, Attentional Control and Processing Speed:

>If controlled problem solving is the central competency that defines fluid intelligence, then many of the same cognitive and brain mechanisms that support controlled problem solving should support performance on measures of gF, and this is indeed the case (Duncan et al., 2000; Kane & Engle, 2002). The most important of these cognitive systems is working memory, specifically the ability to explicitly amd consciously represent information patterns, manipulate these patterns in a controlled fashion, and draw inferences about relations among the patterns (Embretson, 1995). There is debate as to the processes that support working memory and that mediate the relation between working memory and performance on measure of gF. The debates have, nonetheless, narrowed the mechanisms to individual differences in the ability to control attention and inhibit irrelevant information from intruding into conscious awareness (Engle, 2002) or (or perhaps and) individual differences in the speed of processing bits of information (Fry & Hals, 2000; Jensen, 1998). The latter would explain the consistent relation between performance on measures of gF and measures that assess the speed and consistency with which information is processed. Basically, high gF scores are associated with faster information processing and more consistency in the speed of executing the same process across time (Deary, 2000; Kranzler & Jensen, 1991; P.A. Vernon et al., 2000). However, performance on these measures also requires controlled attention, and thus the issue of wether atttention, speed of processing, or a combination underlies individual differences in working memory capacity remains to be resolved.<

David C. Geary, The Origin of Mind, 2005

[If attentional control enables the thinking subject to distinguish between highly relevant, average relevant and irrelevant information and to focus its attention only on highly relevant information while the reasoning process, it would seem very plausible that attentional control strongly correlates with intelligence. ... Unfortunately Engle's research tends to ignore the importance of short term memory.]