Chapter 7: Physiological Measures of Emotion
The startle reflex is a reflexive response in the physical body that occurs in response to an unexcepted, intense stimulus. Types of startle reflexes include knee jerks, neck jerks, and eye blinks. The purpose of the startle reflex is to alert us to danger and to protect our body from harm. The startle reflex is managed by the amygdala. In the laboratory, the startle reflex is measured with the eye blink. The amplitude of the eye blink is positively correlated with the magnitude of the startle reflex. An electromyogram (EMG) is the tool that measures the magnitude of the eyeblink. An electrode is played underneath the lower eyelid on the orbicularis oculi muscle . This electrode measures how much muscle activity occurs after people experience a startle probe. A startle probe occurs when participants experience 50 milliseconds of loud, white noise that was not expected. The startle reflex is a pure measure of the valence of an emotion that occurs in high-arousal situations. In other words, the startle reflex determines whether someone experiences a high-arousal negative emotion or a high-arousal positive emotion. Avoidance emotions occur when someone shows a greater startle reflex to a startle problem compared to baseline startles. Conversely, approach emotions occur when someone shows a smaller startle compared to a baseline/neutral state (Mauss & Robinson, 2009).