Post-hypnotic suggestion improves confidence and speed of memory access with long-lasting effects

The attempt to improve memory has a long tradition. Previous studies do not provide clear evidence concerning the longevity of memory-improving effects which is crucial for clinical applications. In our study, we use the post-hypnotic suggestion of easy remembering to establish long-lasting effects, as post-hypnotic suggestions can be activated with a cue after the hypnotic state. We tested 24 highly suggestible participants in an online study. Participants learned word lists and recalled them later in a recognition memory task where both learned and new words were presented and participants rated their recognition confidence. At the beginning of the study, participants were hypnotized and the post-hypnotic suggestion to remember easily was associated with a cue that participants used during the recognition memory task in the easy-remembering condition. In a control condition, the same participants used a neutral cue. One week later, participants repeated both conditions with new word lists, relying on the same post-hypnotic suggestion they received the week before. Participants were significantly faster and more confident in their recognition ratings in the easy-remembering condition compared to the control condition, and this effect persisted over one week. Crucially, the increased speed and confidence in the easy-remembering condition did not affect memory accuracy; numerically, participants were even slightly better at discriminating old from new words in the easy-remembering condition. These findings demonstrate that post-hypnotic suggestions of easy remembering improve recognition confidence and speed with long-lasting effects, which makes it a promising intervention for patients experiencing subjective memory impairments. All experimental files to run the study in Gorilla are accessible via this link: https://app.gorilla.sc/openmaterials/430668