In many countries, October ushers in the season of ghosts, goblins, and all manner of frightening things that inhabit our deepest fears. While the popularity of Halloween reflects the thrills many derive from a good scare, facing one’s fears is not always fun and games. Our fears can protect us from danger, but they can also hamper individuals from performing the simplest tasks and negatively impact one’s quality of life and mental health.
The study of fear conditioning and fear learning sheds light on how humans and animals develop responses to threatening stimuli. Research often relies on psychophysiological measurements—techniques that capture the body’s physical responses to fear. Key among these measurements are skin conductance response (SCR), electrodermal activity (EDA), heart rate variability (HRV), respiration, and electromyography (EMG).
SCR and EDA track changes in sweat gland activity, providing a direct measure of emotional arousal when a person experiences fear. HRV and respiration rate reveal the autonomic nervous system’s reaction to stress, indicating shifts between sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) states. EMG measures muscle activity, especially facial muscles, to detect subtle expressions or physical tension associated with fear. Understanding these mechanisms has practical applications in understanding and treating anxiety disorders, phobias, and post-traumatic stress disorder (PTSD). By analyzing the body’s automatic fear responses, scientists can develop targeted therapies to help individuals recondition or dampen these reactions.
A study published in the Journal of Behavior Therapy and Experimental Psychiatry used a range of indices to assess learned fear (unconditioned stimulus expectancy or US-expectancy) in individuals. These included both self-reporting and measurements of autonomic response such as skin conductance. Researchers using E-Prime Stimulus Presentation Systems, paired various neutral visual stimuli with unconditioned stimuli in the form of electrical shocks delivered via a constant voltage stimulator coupled with a BIOPAC STM100C amplifier. After a brief break, both neutral stimuli were administered without shock. Skin conductance response data was gathered and analyzed during each phase with a BIOPAC data acquisition and analysis system and software. Results showed a positive correlation between US-expectancy ratings and skin conductance response.
Researchers at the University of Bologna in Italy took a different approach to measuring the psychophysiological mechanisms of fear learning by focusing on HRV. In their study, published in the journal Psychophysiology, they explained that “understanding transient dynamics of the autonomic nervous system during fear learning remains a critical step to translate basic research into treatment of fear-related disorders.” Researchers gathered SCR and electrocardiogram (ECG) data. As with the previous study, mild electrical shocks were applied as unconditioned stimuli and paired with neutral or conditioned stimuli (CS). SCR signals were acquired using a skin conductance transducer attached to the participants’ fingertips connected to a BIOPAC EDA amplifier. ECG data was collected using disposable surface electrodes connected to an ECG100C amplifier. EDA and ECG signals were processed with a BIOPAC data acquisition and analysis system running AcqKnowledge software, which calculated HRV from the ECG data. Researchers concluded that “learned fear elicited a transient heart rate deceleration in anticipation of noxious stimuli.” They added that the study’s findings “provide a proximal measure of the involvement of cardiac vagal dynamics into the psychophysiology of fear learning and extinction, thus offering new insights for the characterization of fear in mental health and illness.”
Another study published in the journal Psychophysiology examines fear learning by applying a broad range of physiological signals and responses to determine which provides the “optimal measurement of human trace fear conditioning.” For this study, researchers compared SCR, pupil size response, heart period response (via ECG), respiration amplitude response, and electromyography (EMG) to measure participants’ responses to electrical current, audio, and visual stimulation. EDA data was gathered via a BIOPAC EDA amplifier, while ECG, EMG, and respiration data were fed to BIOPAC ECG100C, EMG100C, and RSP100C amplifiers, respectively. All data was processed using BIOPAC data acquisition and analysis systems and software. Results of the experiment suggested that startle eye-blink response through EMG provided the most sensitive metric for measuring fear conditioning.
Fear is just one of the emotions that can be studied through the body’s affective response to stimuli. Read more about the relationship between affect and emotion or watch our webinar on Emotion and Objective Physiological Measures.
Are you facing the reality of putting together your own fear-based study? Don’t be afraid to contact your local BIOPAC customer service representative for help finding the right tools for the job.
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