Recent research on relational evaluative conditioning (relational EC) suggests that stimulus
co-occurrence can have a direct effect on evaluations over and above the particular relation
between the co-occurring stimuli. This research is based on a process dissociation approach
where co-occurrence effects are demonstrated via attenuated evaluative learning for
co-occurring stimuli that are connected by contrastive in comparison to assimilative
relations. Instead of attributing such attenuations to an orthogonal influence of stimulus
co-occurrence, we investigated whether (a) contrastive relations tend to produce weaker
evaluations than their assimilative counterparts and (b) such evaluative differences can
inflate evidence for co-occurrence effects on continuous as well as on categorical evaluation
measures. A pilot study (N = 85) confirmed notion (a), while a first experiment (N = 42)
produced preliminary evidence for notion (b) in the context of multinomial processing tree
modeling. We report results from a second, high-powered experiment (N = 252) designed to
produce conclusive evidence for the idea that evidence for co-occurrence effects can be
inflated by evaluative differences between assimilative vs. contrastive relations.