492. The importance of psychophysical errors in subjective judgements of firmness of Cheshire cheese

Abstract

1. Ratings for firmness which were carried out on 150 Cheshire cheese at 2 weeks old, by three judges, were examined so as to extract the expected psychophysical errors.2. It was found that the value for firmness given to any particular cheese tended to be a function of the average firmness of the group of cheese in which it was judged, so that a cheese of a given objective value would be given a different rating according to its position in the series being judged.3. A cheese of a given value presented after a firm one is judged softer than if it had been presented after a soft one. This contrast effect was masked by the influence of the group as described in (2). Nevertheless, it seems probable that contrast effects influence the judgements.4. The frequency distributions of the subjective judgements were examined, and it was noted that the ‘semi-expert’ judge gave subjective values which approximated very closely to a normal distribution, more nearly so than the judgements of the other two judges.5. Reasons are suggested for the differences in the values allotted to the cheese as judged by the different judges.6. Some suggestions are made for eliminating the effects described.