Fear appears fast: Temporal course of startle reflex potentiation in animal fearful subjects

The temporal course of startle reflex modulation and autonomic response pat terns to Fear-relevant and fear-irrelevant pictures in subjects with high a nd low levels of animal fear was investigated. Thirty-eight high-fear and 4 8 low-fear volunteers viewed photos of snakes and spiders and pictures of n eutral and pleasant content. The slides were presented for 6 s or for only 150 ms, depending on the group. Acoustic startle probes were presented at f ive different times after slide onset. Relative potentiation of the startle responses started 300 ms after onset of snake/spider pictures in fearful s ubjects. This fear-potentiated startle effect was maintained for the later probe times and was identical in the 150-ms condition. Fear-relevant pictur es also prompted a sympathetically dominated autonomic response profile in fearful persons. These data support the idea that fear can be activated ver y rapidly, requiring only minimal stimulus input.