Evolutionarily old threat stimuli are likely to require less conscious information processing than threat stimuli of a more recent date. To test thisproposal two differential conditioning experiments, with biological threat stimuli (e.g. snakes) in half the groups and cultural threat stimuli (e.g.guns) in the other half, were conducted. The conditioned (CS+) and the control (CS) stimuli were backward masked during the extinction phase toprevent conscious recognition. The differential skin conductance responding for both biological and cultural threat stimuli survived the maskingprocedure when the conditioned stimuli were directed towards the participants (Experiment 1), but for neither type of CS when stimuli were notdirected towards the participants (Experiment 2). These findings are discussed in relation to the previous finding by O ̈hman and co-workers and inrelation to imminence of threat.