Fear is an essential part of self-defence. If we were attacked by a tiger, fear would trigger an adrenaline rush preparing our bodies for fight or flight. However one in ten people suffers from a phobia, harmless objects or animals trigger an extreme, crippling phobic response. This program takes an unflinching look at both the biological and psychological nature of fear.Using the latest MRI scanning techniques, body imaging, EEG tracing and thermal photography,' this series studies the body's responses to extreme stress. Ultra slow-motion filming captures the physical manifestations of fear, and MRI scanners show its effects on the brain.