For the test trials, discrimination performance in terms of the detectability index d′ was calculated separately for each of the two harmonics (third or fourth mistuned) for each listener and context condition. If the component was mistuned upwards and the listener selected interval 2, this was defined as a hit; if s/he selected interval 1, this was defined as a miss. If the component was mistuned downwards and the listener selected interval 1, this was defined as a correct rejection; if s/he selected interval 2, this was defined as a false alarm. Following Macmillan and Creelman (1991), the first stimulus was treated as a standard, and d′ was determined as z(proportion of hits) minus z(proportion of false alarms), where z(p) is the inverse of the cumulative Gaussian distribution function. Each d′ calculation was based on 640 trials in total. Performance for the context trials was also calculated in the usual way for a 2I-2AFC task, i.e., d′ = [z(proportion of hits) − z(proportion of false alarms)] / √2, but was not the main interest of this study.