Stimulus satiation: effects of repeated exposure to foods on pleasantness and intake.

Frequent and repeated exposure to foods produces stimulus satiation or monotony. To explore further the nature of stimulus satiation, two experiments were conducted. Experiment 1 investigated the influence of initial pleasantness and frequency of intake on monotony. Tests showed that bread and butter was eaten more frequently but was liked less than chocolate. Therefore, normal-weight, healthy males were randomly assigned to either a chocolate condition (CC, N=13) or bread and butter condition (BC, N=16). All subjects received fixed amounts of the assigned food (67g/1473kJ of chocolate or 95g/1355kJ of bread and butter) every day for 22 days. On days 1, 8, 15 and 22 subjects consumed this food ad libitum. Pleasantness of taste and desire to eat chocolate declined significantly over time but no such changes were observed for bread and butter. Experiment 2 examined intake, pleasantness and desire to eat chocolate in 53 subjects over a 15 day period, with 3 conditions: control (CS: N=15), fixed (FS: N=20) and variable (VS: N=18). CS received no chocolate except on test days (days 1, 8 and 15), FS received 67g/1473kJ of chocolate daily and VS received increasing amounts of chocolate from 57g/1251kJ on day 1 to 86g/1888kJ by day 12. Pleasantness and desire to eat chocolate declined over time with this being more pronounced for F and V subjects. However, ad libitum intake increased over time. Both experiments demonstrated significant changes in pleasantness and desire to eat chocolate, but no commensurate decline in intake. Thus, although stimulus satiation occurred for subjective ratings of pleasantness and desire to eat chocolate, intake remained unaffected. This apparent dissociation between pleasantness and intake may reflect different processes underlying liking and wanting.