The development of a same–different inspection time paradigm and the effects of practice

Experiment 1 introduced a same–different letter discrimination task conducted with the inspection time (IT) procedure. The letter IT task was found to eliminate the use of systematic strategies, such as apparent movement and flash cues; in the past, such strategies have made the IT–IQ relation difficult to interpret. The IT–IQ relation was found to be as strong under the new task as that found under the typical task, with higher-IQ participants outperforming their lower-IQ counterparts across both IT tasks. Experiment 2 explored the effect of practice on IT, as assessed by the letter IT task, and the impact that it may have on the IT–IQ relation. Practice resulted in a significant linear increase in accuracy and an attenuation in the IT–IQ relation; this improvement cannot simply be attributed to more efficient use of response strategies. These findings suggest that at least one component of mental speed that is sensitive to practice may be an important factor underlying the correlation between IT and IQ.