Measuring pupillary response is a common approach for assessing mental states. A correction process for the pupillary baseline was required to derive a meaningful conclusion from the pupillary response. On the other hand, the association between pupillary baseline and subsequent stimulus-evoked pupillary response differs between research. 

Researchers employed subtractive and proportional baseline adjustments to assess the study’s outcomes. Furthermore, they modulated the pupillary baseline during the baseline phase using mental effort or brightness to see if the subsequent stimulus-evoked pupillary responses were impacted. They discovered that a bigger pupillary baseline modified by a higher mental effort decreased the mental effort-evoked pupillary response, but the baseline adjusted by brightness had no effect. Also, with a smaller pupillary baseline manipulated by a brighter disc, the luminance-evoked pupillary response was reduced, but it was unaffected with the baseline adjusted by mental effort. Subtractive and proportionate baseline adjustments might yield the desired outcomes. 

The findings indicated that the mental effort manipulated pupillary baseline interacts with the subsequent mental effort elicited pupillary response but not with the luminance elicited the pupillary response and that the luminance manipulated pupillary baseline interacts with the subsequent luminance elicited pupillary response but not with the mental effort elicited a pupillary response. It was critical to explore how to simultaneously manage the pupillary baseline and the following pupillary reaction.

Reference: jov.arvojournals.org/article.aspx?articleid=2783435