It has recently been found that during recognition memory tests participants’ pupils dilate more when they view old items compared to novel items. This thesis sought to replicate this novel ‘‘Pupil Old/New Effect’’ (PONE) and to determine its relationship to implicit and explicit mnemonic processes, the veracity of participants’ responses, and the analogous Event-Related Potential (ERP) old/new effect. Across 9 experiments, pupil-size was measured with a video-based eye-tracker during a variety of recognition tasks, and, in the case of Experiment 8, with concurrent Electroencephalography (EEG). The main findings of this thesis are that:
- the PONE occurs in a standard explicit test of recognition memory but not in “implicit” tests of either perceptual fluency or artificial grammar learning;
- the PONE is present even when participants are asked to give false behavioural answers in a malingering task, or are asked not to respond at all;
- the PONE is present when attention is divided both at learning and during recognition;
- the PONE is accompanied by a posterior ERP old/new effect;
- the PONE does not occur when participants are asked to read previously encountered words without making a recognition decision;
- the PONE does not occur if participants preload an “old/new” response;
- the PONE is not enhanced by repetition during learning.
These findings are discussed in the context of current models of recognition memory and other psychophysiological indices of mnemonic processes. It is argued that together these findings suggest that the increase in pupil-size which occurs when participants encounter previously studied items is not under conscious control and may reflect primarily recollective processes associated with recognition memory
