ERP correlates of the decision time-IQ relationship: The role of complexity in task- and brain-IQ effects

Relatively little is known about the dynamic neural processes most critical to chronometric effects, and the ways in which task demands influence their various contributions to intelligence. The present study (n = 111) used the Hick paradigm to measure the effects of task complexity on decision time (DT) and event-related potentials (ERPs), and on their relations in turn with IQ. The surface Laplacian transform increased the spatial resolution of the recorded neural activity, and revealed four ERP components in the time range of DT. Zero-order correlations of DT, ERP amplitudes and latencies, and IQ were used to motivate multilevel models (MLM) that examined moderating effects of IQ on potential condition effects. Although DT consistently increased with greater complexity and was related to IQ across conditions, IQ did not moderate the increase in DT with increasing complexity. Similarly, while most ERP amplitudes and latencies also increased over conditions, and often predicted DT, only the amplitude of the P2 component was associated with IQ. Unlike the effects for DT, while IQ did not moderate P2 amplitudes during simple DT, it did predict greater increases between simple and choice conditions. Overall, these findings highlight the need to distinguish neural correlates of adaptive performance in general from those related to individual differences.