Learning to fear novel stimuli by observing others in the social affordance framework

Fear responses to novel stimuli can be learned directly, through personal experiences (Fear Conditioning, FC), or indirectly, by observing conspecific reactions to a stimulus (Social Fear Learning, SFL). Although substantial knowledge exists about FC and SFL in humans and other species, they are typically conceived as mechanisms that engage separate neural networks and operate at different levels of complexity. Here, we propose a broader framework that links these two fear learning modes by supporting the view that social signals may act as unconditioned stimuli during SFL. In this context, we highlight the potential role of subcortical structures of ancient evolutionary origin in encoding social signals and argue that they play a pivotal function in transforming observed emotional expressions into adaptive behavioural responses. This perspective extends the social affordance hypothesis to subcortical circuits underlying vicarious learning in social contexts. Recognising the interplay between these two modes of fear learning paves the way for new empirical studies focusing on interspecies comparisons and broadens the boundaries of our knowledge of fear acquisition.