Faster equals smarter? A psychopharmacological analysis of the relationship between mental speed and mental abilities

Individual differences in the speed of information processing have been suggested to give rise to individual differences in general intelligence. Consistent with this hypothesis, reaction times and latencies of event-related... [ view full abstract ]

Individual differences in the speed of information processing have been suggested to give rise to individual differences in general intelligence. Consistent with this hypothesis, reaction times and latencies of event-related potential have been shown to be substantially associated with cognitive abilities. In particular, general intelligence has been most strongly related to the efficiency of information transmission from frontal attention and working memory processes to temporal-parietal processes of memory storage, as measured by latencies of event-related components of the EEG associated with higher-order cognitive processes. Theoretical accounts of this association suggest a causal relationship between mental speed and general intelligence in the way that a greater mental speed facilitates information processing and thus contributes to better performance in intelligence tests. However, all of these studies have been correlational in nature. Bridging the fields of correlational and experimental psychology, the present study used a double-blind within-subject design to assess the effects of nicotine administration on the speed of information processing and intelligence test performance in 47 participants. While nicotine administration decreased both reaction times, F(1,43) = 5.29, p = .026, ω² = .08, and P3 latencies, F(1,43) = 7.32, p = .010, ω² = .12, in comparison to a placebo condition in the Sternberg memory scanning task, there was no effect of nicotine on intelligence test performance, F(1,43) = 3.25, p = .078, ω² = .05. These results contradict theories proposing that a greater speed of information processing causes greater intelligence. Instead, they suggest that some structural properties of the brain may affect both the speed of information processing and general intelligence and may thus give rise to the association between mental speed and mental abilities.