Procedure
The pre-experimental instructions were translated into Dutch. The procedure used with group WITHIN was an exact replication of the procedure used with group INTER in Experiment 1. Participants in group BETWEEN received exactly the same habituation and acquisition phases, but differed in the generalization test phase. Here, the test phase consisted of 6 nonreinforced presentations of only one of the generalization test stimuli. Participants from this group were divided in 8 subgroups (10 participants each), so that the entire set of generalization stimuli was tested across subgroups. Next, the generalization test stimulus was extinguished further in each subgroup by another 6 nonreinforced presentations. Finally,the S+ and S− were each presented three times again, without outcome. Trial presentations were randomized with the restriction of no more than 2 consecutive identical trials.