Missed by an inch or a mile? Predicting the size of intention-behaviour gap from measures of executive control.

Failing to achieve healthy intentions can have a direct impact on subsequent health. The extent of this impact is partially determined by the size of the discrepancy between intentions and behaviour, that is, on whether an unachieved behavioural target is missed by an inch or a mile. Over two studies, measures of 'executive control' ability were used to predict the size of the intention-behaviour gap for two dietary behaviours - eating fruits and vegetables and snacking. In Study 1, participants (n=50) reported intended dietary intake, completed objective and self-report measures of executive control ability and recorded actual dietary intake over 3 days with computerised diaries. Using multiple regression, general executive control ability was found to account for 16-23% of the variance in the size of intention-behaviour gap for both the dietary behaviours. In Study 2 (n=52), deviation from intentions about snacking was significantly related to individual differences in prepotent response inhibition. Overall, individuals with weak executive control ate less fruits and vegetables and more snacks than intended. Intention-behaviour 'failures' are not homogenous, but instead vary predictably with the availability of executive control resources. This suggests that individuals with large intention-behaviour shortfalls may benefit from interventions designed to reduce the demands on executive control.