Abstract
There is variability in rated sensitivity to the bitter compound, 6-n- Propylthiouracil (PROP). While polymorphisms of the TAS2R38 gene account for between 55 and 85% of the variance observed, it is likely that other factors also influence PROP ratings. In order to examine some of these factors, the participants in the Dunedin Multidisciplinary Health and Development Study rated PROP intensity. This study has followed a birth cohort of 1037 individuals since 1972. Ninety-six percent (n = 972) of living participants were re-assessed in 20042005 (aged 32) and their responses to 0.0032M of PROP were measured using the general Labelled Magnitude Scale (gLMS). Participants were also asked to imagine the brightest light ever seen and to rate this sensation on the gLMS. The data were analysed separately by sex. Factors predicting PROP ratings were: childhood IQ scores (higher IQ predicting lower PROP rating), childhood SES scores (higher SES predicting lower PROP rating for women) and scores on the gLMS for the imagined brightest light (higher light rating predicting higher PROP rating) (final models: r2 = 0.168 for women, r2 = 0.087 for men). Neither childhood IQ nor childhood SES predicted ratings for the imagined brightest light. These finding indicate that psychosocial factors may account of some of the variance in PROP ratings not explained by genetics. Funding was provided by the Health Research Council of New Zealand.