Psychophysical approaches to neural efficiency and psychometric intelligence: Contrasting the coding efficiency hypothesis and the temporal resolution power hypothesis
A central feature of the resource consumption approach to intelligence is that individuals with above-average mental ability utilize the available neural resources more efficiently than below-average individuals. Neural efficiency has also been hypothesized to play a crucial role in perceived duration. According to the coding efficiency hypothesis, perceived duration is considered to reflect the amount of neural activity required for temporal processing of a given stimulus. As an alternative approach, the temporal resolution power (TRP) hypothesis suggests a positive functional relationship between temporal sensitivity and neural efficiency. According to the hypothesis of temporal coding efficiency, mental ability is expected to be negatively related to perceived duration, while the TRP hypothesis predicts a positive correlational relationship between temporal sensitivity and mental ability. The present study was designed to directly test the predictions derived from both these hypotheses. For this purpose, general intelligence (psychometric g) was assessed in 190 participants who also performed an auditory temporal discrimination task. In a next step, individual levels of psychometric g were correlated with psychophysical measures of perceived duration and temporal sensitivity, respectively. While there was a highly reliable positive correlation between temporal sensitivity and psychometric g, no evidence for a functional relationship between psychometric g and perceived duration could be found. The absence of a functional link between perceived duration as an indicator of coding efficiency and psychometric g suggests that coding efficiency reflects aspects of neural efficiency unrelated to psychometric intelligence. On the other hand, temporal sensitivity appears to be a valid psychophysical indicator of aspects of neural efficiency involved in psychometric g.