Taxonomic relations evoke more fear than thematic relations after fear conditioning: An EEG study

When fear is generalized, knowledge based on concepts is also retrieved. Concepts have two very different relations: thematic relations based on the co-occurrence of events or scenarios, and taxonomic relations based on similarity or shared features. However, it remains unclear whether thematic and taxonomic relationships differentially affect fear generalization. To clarify the underlying cognitive mechanisms of these relations, the current study combined the classical fear conditioning procedure with electroencephalography (EEG). Forty participants were conditioned to a neutral word by pairing the presentation of the word with an unpleasant electrical pulse. A different stimulus was not paired with the electrical pulse. Next, during generalization testing, thematically related or taxonomic-related words were presented. Behavioral responses (shock expectancy and response time) and brain responses (event-related potentials [ERP] and oscillation activity) were recorded. Behavioral results showed that taxonomic relations initiated higher shock expectancy compared with thematic relations, and that conceptual relations did not affect response times. Taxonomic relations induced larger P2 components than thematic relations, and danger generalization stimuli initiated smaller P600 components than safe generalization stimuli. In addition, the magnitudes of alpha and beta oscillations were larger for danger generalization stimuli. These results suggested that taxonomic stimuli generalize broader responses compared with thematic relations after fear conditioning. Therefore, we report a possible new electrophysiological evidence for the presentation of fear generalization. These findings aid our understanding of fear generalization at the concept level and have clinical implications for the cognitive treatment of anxiety disorders.