Chromatic and luminance losses with multiple sclerosis and optic neuritis measured using dynamic random luminance contrast noise

We measured thresholds for detecting changes in colour and in luminance contrast in observers with multiple sclerosis (MS) and/or optic neuritis (ON) to determine whether reduced sensitivity occurs principally in red-green or blue-yellow second-stage chromatic channels or in an achromatic channel. Colour thresholds for the observers with MS/ON were higher in the red-green direction than in the blue-yellow direction, indicating greater levels of red-green loss than blue-yellow loss. Achromatic thresholds were raised less than either red-green or blue-yellow thresholds, showing less luminance-contrast loss than chromatic loss. With the MS/ON observers, blue-yellow and red-green thresholds were positively correlated but increasing impairment was associated with more rapid changes in red-green thresholds than blue-yellow thresholds. These findings indicate that demyelinating disease selectively reduces sensitivity to colour vision over luminance vision and red-green colours over blue-yellow colours.

Spontaneous comparisons with others in gay men´s judgements of HIV risk

In studies on ‘unrealistic optimism’ (UO), when people are asked questions designed to make them compare their risk of experiencing an undesirable event with that of the average person, they tend to respond that their risk is lower. This study investigated whether comparisons of own and others’ risk also occur spontaneously, unprovoked by such questions. Gay men uninfected with HIV (n¼50) were asked to think aloud about their risk of becoming infected; their comments were audiotaped and analysed. Over half the men added comments relating to others’ risk. The phrasing of these comments and the reported basis for them are described. The men represented others’ risk as relatively high, own risk as relatively low. In the case of onethird of the men, it seemed possible to be confident that a comparison was being made. The findings suggest that comparisons of own and others’ risk do occur spontaneously and that, while the judgements made in UO studies do not capture all the characteristics of those made spontaneously, they resemble them in important ways.