RARELY OCCURRING HEADACHES AND RARELY OCCURRING BLINDNESS - IS RARELY=RARELY - MEANING OF VERBAL FREQUENTISTIC LABELS IN SPECIFIC MEDICAL CONTEXTS

In three experimental studies, factors were examined which might influ ence the interpretation of verbal frequentistic labels in a specific c ontext (i.e. side effects of medical drugs). In Study 1, we directly a ssessed subjects' numerical equivalents of three verbal labels (recomm ended for use by the German Federal Health Agency), which were embedde d in stylized leaflets for medical drugs; we compared the estimates wi th those obtained in a context-free situation. The major findings were that (1) subjects' numerical equivalents for the verbal labels were c learly lower in the context condition than in the context-free situati on, (2) subjects' interpretations appeared to depend on the seriousnes s of the side effects, but (3) this dependency disappeared when explic it base rates were provided. In Studies 2 and 3, we indirectly examine d the influence of the seriousness of the side effects, their frequenc y, and of the mode of expression (verbally versus numerically) by aski ng for risk judgments for and choices between drugs. Results of partic ular importance were that (1) seriousness and frequency of side effect s had the same influence on judgments and choices but the mode of expr ession had no significant effect on either judgments or choices; (2) w hen subjects' individual numerical equivalents of verbal labels were u sed in the leaflets, numerically described drugs were judged equally r isky as verbally described drugs but were significantly preferred for consumption. These findings have theoretical relevance for research on the processing of verbal and numerical frequentistic expressions as w ell as a number of practical implications for the communication of med ical information.