The differential similarity of positive and negative information – an affect-induced processing outcome?

People judge positive information to be more alike than negative information. This good-bad asymmetry in similarity was argued to constitute a true property of the information ecology (Alves, H., Koch, A., & Unkelbach, C. (2017). Why good is more alike than bad: Processing implications. Trends in Cognitive Sciences, 21, 69–79). Alternatively, the asymmetry may constitute a processing outcome itself, namely an influence of phasic affect on information processing. Because no research has yet tested whether phasic affect influences perceived similarity among stimuli, we conducted 5 Experiments that also tested whether phasic affect can account for the higher judged similarity among positive compared to negative stimuli. In three experiments, we affectively charged pictures of different Pokemon by pairing them with monetary gains and losses (Exp. 1a, 1b) as well as positive and negative trait words (Exp. 2); yet, the evaluative charge did not differentially influence perceived similarity among the Pokemon. Experiment 3 replicated the basic similarity asymmetry among positive and negative words, and found that it was unaffected by externally induced phasic affect. Experiment 4 showed that phasic affect had no influence on perceived similarity of non-evaluative words either. We conclude that albeit a weak influence of phasic affect on perceived similarity of stimuli cannot be ruled out entirely, it can most likely not account for the typically medium to large sized asymmetry in similarity among positive and negative stimuli.     

The effects of direction similarity in visual working memory: Behavioural and event-related potential studies

Object similarity can improve visual working memory (VWM) performance in the change-detection task, but impair the recognition performance when it occurs at retrieval of VWM in the recognition task. The effect of direction similarity is an issue that has not been well resolved. Furthermore, electrophysiological evidence in support of the mechanisms that underlie the effects of similarity is still scarce. In the current study, we conducted three behavioural experiments to examine the effects of direction similarity on memory performance with regard to both the encoding and retrieval phases of VWM and one event-related potential (ERP) experiment to explore the neural signatures of direction similarity in VWM. Our behavioural studies indicated that direction similarity improved performance when it occurred at the encoding phase but impaired performance when it occurred at the retrieval phase. Moreover, the ERP experiment showed that the amplitude of the contralateral delay activity (CDA) increased with the increasing set size for similar but not dissimilar directions. In addition, the CDA amplitude for similar directions was lower than that for dissimilar directions at set size 2. Taken together, these findings suggest that direction similarity at encoding has a positive effect on VWM performance and at retrieval has a negative effect. Given that VWM capacity depends on information load and the number of objects, the positive effect of similarity may be attributed to reduced information load of memory objects.