High and low alexithymia scorers were confronted with a modified visual oddball task that allowed the study of categorical perception of emotional expressions on faces. Participants had to quickly detect a deviant (rare) morphed face that shared or did not share the same emotional expression as the frequent one. Expected categorical perception effects, which were also neurophysiologically indexed, showed that rare stimuli were detected faster if they depicted a different emotional expression compared to rare stimuli depicting the same emotional expression (...) than the frequent one. Even if no differences were observed at a behavioural level, high alexithymia scorers evidenced overall delayed neurophysiological responses in components related to the attentional processing of rare emotional faces. Moreover, the categorical perception effects for event-related components associated with the attentional processing were smaller in high alexithymia scorers and were even absent for anger. These results show that high alexithymia scorers present discrimination delays that are already observed at the attentional level. (shrink)