Diffusion modeling and intelligence: Drift rates show both domain-general and domain-specific relations with intelligence.

Several previous studies reported relationships between speed of information processing as measured with the drift parameter of the diffusion model (Ratcliff, 1978) and general intelligence.Most of these studies utilized only few tasks and none of them used more complex tasks.In contrast, our study (N = 125) was based on a large battery of 18 different response time tasks that varied both in content (numeric, figural, and verbal) and complexity (fast tasks with mean RTs of ca.600 ms vs. more complex tasks with mean RTs of ca.3,000 ms).Structural equation models indicated a strong relationship between a domain-general drift factor and general intelligence.Beyond that, domain-specific speed of information processing factors were closely related to the respective domain scores of the intelligence test.Furthermore, speed of information processing in the more complex tasks explained additional variance in general intelligence.In addition to these theoretically relevant findings, our study also makes methodological contributions showing that there are meaningful interindividual differences in content specific drift rates and that not only fast tasks, but also more complex tasks can be modeled with the diffusion model.