LA SPECIFICITÀ DEL PLACEBO E IL SUO EFFETTO SUL BENESSERE SOGGETTIVO MA NON SULL’AUTO-VALUTAZIONE COGNITIVA

It is investigated whether placebo produces true psychological effects or it follows from experimental and/or experimenter biases. This investigation was done by asking either if placebo produces effects that are specific to emotional dimensions (well-being subjective and social, sickness) but not to cognitive dimensions (language, attention, memory), or if it is produced by biases and hence it is non-specific on both dimensions. A within-subject design on 38 adults was employed, with Likert self-evaluations. Placebo was a “drug of alternative medicine” (which was actually water) and the explicit information given in two experiments was about substance usefulness which was either reduction of anxiety and depression, or increase of memory and concentration. Experiments were run in ecological setting with drug self-intake at subjects’ residence. Results showed that, independently of explicitly declared usefulness, placebo effect was specific to emotional dimensions (increase of well-being and decrease of sickness), but not to cognitive dimensions. Expectance about substance usefulness and placebo effect were additive. Newly discovered strong “taste illusions” on placebo palatability were found (36 over 38 subjects). Delay from placebo intake to its effect on well-being upsurge was subjectively estimated to occur around 39 minutes later.