Post-hypnotic suggestions of easy remembering increase subjective confidence of recognition with long-lasting effects

Human memory performance is affected by subjective processes. Previous research has shown that once information has been learned, forgetting only means that it cannot be accessed any more while the information itself is still present. There are case reports that hypnosis techniques can make forgotten information accessible again. In our current study, we investigated if post-hypnotic suggestions of easy remembering can increase memory performance and if this effect is stable over time. We tested 24 highly suggestible participants in an online study. Participants were hypnotized by a recorded audio text and suggested that their ability to remember information easily is associated with a piece of paper with the letter E for easy remembering on it. They also wrote a K for control on another piece of paper that had no associated meaning. Then, participants learned word lists and recalled them later in two conditions. In the control condition, participants used the K paper when remembering the learned words, in the experimental condition, they used the E paper triggering the post-hypnotic suggestion of easy remembering. One week later, this procedure was repeated with new word lists. In the recognition task, participants indicated for each word how sure they are that they have learned it before. Here we show that in the E condition, participants identified the words in the recognition task with significantly increased confidence as old or new compared to the K condition. This effect was still significant one week later. Objective accuracy of memory performance was very high in both conditions, we did not detect a difference between conditions. This is the first study showing that subjective confidence of recognition can be improved by a post-hypnotic suggestion of easy remembering with long-lasting effects. All experimental files to run the study in Gorilla are accessible via this link: https://app.gorilla.sc/openmaterials/43066