In this two-alternative forced choice (2-AFC) task, subjects had to indicate for one half of the CS set (10 CS+ and 10 CS−) first, whether a stimulus had been paired with a shock or not during conditioning and second, whether the shock had been administered to the right or left index finger. A d’ sensitivity measure (Green & Swets, 1966) was calculated for recognising a CS belonging to the correct affective category and for reporting the correct hand if a CS+ had been presented. For statistical evaluation of subjects’ performance, the d’ values were tested against 0 with one-sample t-tests. (ii) With the other see more half of the CS set, a complete pair comparison
was performed, involving the presentation of all possible pairs of 20 CS and resulting in 190 comparison trials. This CS pair comparison task involved the subsequent presentation of two click-tones with a temporal delay of 750 ms. Subjects had to decide which one of the two stimuli they found more pleasant (2-AFC). The statistical analysis was restricted to comparisons of pairs from different affective categories. The mean percentage of preference for the CS− (or rejection PI3K inhibitor of the CS+) was tested against chance level (50%) to determine whether subjects were able to differentiate CS+ and CS− on a more implicit
level of processing. (iii) The third task involved the affective priming of positive and negative adjectives with the CS, which constituted an indirect measure of stimulus valence (e.g. Spruyt et al., 2007). Forty positive and 40 negative adjectives were selected from a set established by Kissler et al. (2007), who provided valence and arousal ratings from a reference group (n = 45). The words did not differ with respect to mean word length (negative adjectives, 7.2 characters;
positive adjectives, 7.5 characters) or arousal (negative, mean ± SD, 5.85 ± 1.97; positive, 5.83 ± 2.2), but were significantly different in terms of valence ratings (negative, 1.67 ± 0.81; positive, 7.86 ± 1.11). Each of the 40 click-like tones was presented twice, once as a prime for a negative and once for a positive adjective, resulting in 80 priming trials, half of which were congruent (CS− and positive adjective, CS+ and negative adjective) and half of which Clomifene were incongruent (CS+ and positive adjective, CS− and negative adjective). Each trial consisted of the presentation of a CS tone that was followed by the adjective with an inter-stimulus interval of 300 ms (cf. Hermans et al., 2003). Subjects had to decide whether the adjective’s meaning was positive or negative in an evaluative decision task and were instructed to respond as fast and as accurately as possible to the presented words. We restricted the analysis to correct responses and further excluded reaction times (RTs) that were above or below 2 SD of the individual mean, rejecting 7.01% of the trials.