Beyond Expectations: Nocebo Suggestion Affects Cognitive Performance in Older Adults

BACKGROUND: Placebo and nocebo effects have been extensively studied in pain management and motor performance, yet their impact on cognitive performance remains largely unclear. Understanding these effects is particularly relevant for designing interventions that leverage positive expectations to enhance cognitive outcomes while mitigating negative expectations, especially for older adults, who often face age-related cognitive decline and could benefit from tailored interventions. AIM: This study examined whether placebo and nocebo effects manifest in healthy older adults in an online setting, where the conventional participant-experimenter interactions are absent, and explored the consistency across sensory modalities. METHOD: Participants completed an adaptive oddball task in auditory and visual modalities before (PRE) and after (POST) exposure to an inert acoustic stimulation. Prior to this stimulation, they were randomly assigned to one of three groups, receiving neutral (control), positive (placebo), or negative (nocebo) information about the potential effects of the intervention. RESULTS: Only the nocebo group exhibited performance changes at POST consistent with the verbal suggestion across both sensory modalities, showing a decline or a lack of practice effect. However, the objective nocebo effect was not accompanied by a negative shift in subjective expectancy or perceived stimulation efficacy. In contrast, although participants in the placebo group expected their performance to improve as intended by the manipulation, their performance remained unchanged, and they did not perceive any beneficial effect from the stimulation. CONCLUSION: These findings suggest that, even without direct participant-experimenter interaction nocebo effects are observable in cognitive performance in older adults. However, under the same conditions, placebo effects may be limited to subjective expectations rather than objective gains. This highlights the need to consider additional factors such as motivation, engagement, and individual differences, especially in online contexts where external reinforcement is limited.