The effect of variations in the presentation of oral contraceptive risk information on perceived safety was investigated. Four tests of the hypothesis that consumers focus on the absolute value of the numbers presented when assessing risk probabilities were performed with the following results: (1) when base rates are given, risks are perceived as less likely than when base rates are not given; (2) risks seem smaller when the information provided focuses on the number that will not die than when the number of expected deaths is presented; ( 3 ) contrary to our expectation, respondents do not focus on foreground numbers when risk was represented in an 'X out of Y occurrences' format; (4) respondents judged a risk of '4.15 times greater' as less likely than when the information was presented as '415% greater risk'. We concluded that consumers convert statistical risk information into judgements about the magnitude of the number presented (small or large number) and utilize this more meaningful information when making risk judgements.Individuals in modern society are frequently required to make decisions that involve grave potential risk. As voters and consumers we have to make 'safe enough' decisions about a large and diverse array of topics which include nuclear energy, food irradiation, surgical procedures, air and water quality, and drug use. There is a large body of psychological research that shows that estimates of the probability of risky events are affected by multiple sources of error. People tend to greatly misuse odds of greater than 50:l (Slovic, Fischoff and Lichtenstein, 1977), underutilize base rates (Einhorn and Hogarth, 198l), interpret mathematically equivalent forms of statistical information in different ways (Halpern and Blackman, 1985), ignore or significantly underestimate the cumulative nature of probabilistic events (Shaklee, 1987), weigh more heavily the testimonials of one or a few people than data generated from large samples (Hogarth, 1980), overestimate events that are readily available in memory and/or appear representative of the underlying phenomenon (Tversky and Kahneman, 1974), and believe that favourable events are more likely to occur than unfavourable ones (Beyth-Marom, Dekel, Gombo and Shaked, 1985;Halpern and Irwin, 1973).Decisions involving oral contraceptives should be immune to many of these difficulties because potential consumers are provided with objective probability 088&4080/89/03025 1-10$05.00 0 1989

Judgments of contour strength or saliency for twenty-four illusory-contour configurations were subjected to a confirmatory factor analysis. A four-factor model that posited the involvement of simultaneous contrast, linear effects (assimilation and dissimilation), depth/completion cues, and feature analyzers accounted for a substantial proportion of the variance in judgments of illusory-contour strength. The hierarchical addition of a fifth factor, diffuse illusory contours, significantly improved the overall fit of the model, but added little to the proportion of explained variance. The taxonomic approach adopted provides support for a multiprocess model of illusory-contour perception.

Four theories of illusory-contour perception are reviewed--brightness contrast (simultaneous contrast, assimilation, and dissimilation), depth/completion, partial activation of neural feature analyzers, and the diffuse-sharp dichotomy. It is concluded that the processes and mechanisms involved in illusory-contour perception most likely depend upon the stimulus elements used in the illusory-contour display.

The perceived depth associated with subjective contours was studied with a three-level subjective contour configuration. An analysis of subjects' size judgments showed significant size-constancy scaling consistent with the prediction that subjects would perceive the various subjective surfaces as superimposed upon one another in depth. Direct depth estimations, however, showed only weak depth effects, easily reversed by conflicting depth cues, and observed with real, as well as subjective contours. The discrepant results point to the possibility of different functional depth cues for the two tasks. The order of tasks, indicative of priming, further suggested that depth processing may be secondary to pattern recognition rather than being causal in the formation of subjective contours.