Dissociative experience and mood-dependent memory

Abstract

Amnesia is the main phenomenon in dissociative experiences. The present study investigated whether amnesia in participants with frequent dissociative experiences depended on state-dependent memory. Undergraduates scoring high (n=32) or low (n=32) on the Dissociative Experiences Scale Version-II (DES-II) participated in this experiment. Mood induction and a remember/know task were used in a typical mood-independent memory design. In the inconsistent mood state condition, participants in the high DES group showed decreased memory performance compared to the low DES group. These results were attributed to the recollection components of recognition and not to the familiarity component. Therefore we concluded that the normal population with highly frequent dissociative experiences showed strong state-dependent memory and had a memory bias in the recollection component of memory.

Acknowledgements

We would like to thank Dr Takashi Horiuchi and Dr Takehiko Nishimoto for their help with the experimental material and devices.

Notes

¹The mood-induction scripts were made by one experimenter, checked and refined by the other experimenters, and then used during the preliminary investigation to confirm their effectiveness. The scripts used in this experiment induced significant differences on the PANAS scores in the simple imagination task of the scene described in the induction script. We conducted t-tests for the PANAS scores in this preliminary investigation. The imagination task was administered twice to one participant in order to mimic the mood-dependent memory paradigm. In addition, the participants were randomly assigned to either the same or different mood group, again in accordance with the mood-dependent paradigm. The results indicated that the script successfully induced the target mood. The positive mood-induction scores at the first and second induction showed a significant difference depending on the type of script, for first induction, t(10) = 5.13, p<.001; for second induction, t(10) = − 3.06, p<.05. Moreover, the negative mood-induction score showed a significant difference depending on the type of script, for first induction, t(10) = − 2.85, p<.05; for second induction, t(10) = − 2.73, p<.05. The score indicated that 83.3% of all inductions successfully induced the target mood.

²In our study, the overall hit rate was separated into “remember” and “know” hit rates. “Remember” and “know” hit rate was calculated by the following formulas:

²Remember hit rate = the number of hits in remember judgement/the number of remember judgements.

²Know hit rate = the number of hits in know judgement/the number of know judgements.