Individual differences in tonic and phasic pupillary indices of cognitive abilities: Preliminary evidence for a task- and state-specific account

The present thesis gathers findings from three empirical studies in which we examined the cognitive basis of individual differences in phasic and tonic pupil cognitive responses. Some previous studies have reported a positive relationship between tonic and phasic pupil sizes and cognitive traits, such as general intelligence (gF) and working memory capacity. However, other studies have shown either a negative or no relationship. These findings have been usually accounted for by relatively stable differences in the function of the brain’s locus-coeruleus norepinephrine (LC-NE) system and in how much mental resources highly intelligent individuals have or how efficiently they are able to allocate their resources in general. Our findings, however, challenge these accounts and indicate that individual differences in pupil cognitive responses are driven by the task- and state-specific cognitive factors rather than general cognitive traits. In other words, the pupillary responses in both MOT and Posner tasks showed that the high performers had larger TEP sizes than low task performers, but only when the task was very demanding and more mental effort was required. When the task was not very demanding, high performers seemed more efficient in the allocation of their resources since they outperformed the low performers without investing more resources (i.e., no significant difference in TEP sizes between groups). These results may indicate that the neuromodulatory function of the LC-NE system is mediated by individuals’ level of cognitive functioning in a specific state and task. These differences may also have visual consequences, especially in the real-life situations, by modulating the trade-off between visual sensitivity and acuity in a statespecific fashion. The cognitive correlates of individual differences in tonic baseline pupil sizes also seemed to also be state- and task-specific. That is, we found a positive relationship between mean pretrial baselines and overall performance, but only in the MOT task. Also, none of the indices of general cognitive abilities were related to the average size of resting-state or pretrial baseline pupil sizes. WMC, however, was positively related to the coefficient of variation of resting-state baselines. This higher variability may be accompanied with a more dynamic and explorative mode to search randomly for internal or external rewarding sources. But it may also reflect the arousal-related regulations. Results also showe