Exploring cerebral and pupillometric markers of suggestibility in healthy elderly individuals: forensic implications.

The present study aims to explore potential cerebral and pupillometric indicators of suggestibility in healthy elderly individuals. Specifically, Interrogative Suggestibility (IS) was assessed through the administration of the Gudjonsson Suggestibility Scale (GSS-2). From the results of the GSS-2 two groups were identified: one exhibiting a low degree of suggestibility (Low GSS group) and the other displaying a higher degree of suggestibility (High GSS group). Resting-state EEG frequency bands (hd-EEG 128-channel system) and pupil diameter (Eyelink Portable Duo eye-tracker) were then analyzed in relation to these suggestibility levels. Based on Cognitive Load Theory framework (CLT), which is closely related to arousal, it was hypothesized that high suggestibility was associated with an elevated baseline arousal: higher pupil dilation, decreased alpha activity and increased theta activity. Results revealed significant differences in pupil dilation, but no overall differences in frequency bands. However, significant results were found on EEG frequency activity and the indicators of resistance to the interviewer’s pressure: Shift and Yield 2, suggesting the crucial role of emotional factors linked to coping strategies. Indeed, suggestibility is a multi-faceted phenomenon that is mediated by various cognitive and personality variables which can be exacerbated under certain conditions. In forensic settings, accounting for suggestibility is particularly critical in interviewing procedures, especially in vulnerable individuals, such as elderly population. The present study lays the groundwork for further research aimed at enhancing the assessment of testimonial validity by exploring physiological markers of suggestibility.