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Why are we interested in psychophysiological measurements? Which measurements are these exactly? By “measurements,” we are talking about micro-facial expressions, pupil dilation, peristaltic contractions of the intestines, heart activity, breathing patterns, electrodermal activity, and other responses not visibly apparent.

In the 1880s, an English philosopher named William James was among the first to explore what constitutes an “emotion.” James believed that everything, big and small, that happens to us and around us elicits a constant stream of feelings and responses. These responses can range from indifference, fear, excitement, happiness, stress—virtually the full gamut of the human emotional palette.

Why does this happen and how do we measure it?

There is always a response in our bodies as a consequence of input delivered via our senses, and there is a resulting “feeling” that happens. Sometimes the feeling doesn’t have much impact but at other times, its effect is profound. The term “emotion” is the label that we assign to these feelings. These feelings result in a response that affects our physiology. These physiological responses to ongoing events are objectively measurable and referred to as “affect.”

Data enters the brain via our senses, but it takes a small period of time to process the input; about 50 milliseconds if the event is a sound, and 100 milliseconds if visual. When data comes in, it travels through various neural pathways and our response to it is informed by our previous experiences. An extreme example to external input causing profound affective changes would be in someone with post-traumatic stress disorder (PTSD), in which certain sounds, or other situational input can trigger pronounced panic or discomfort. People with phobias (for example, fear of cats) will exhibit physiological changes far out of proportion to the actual danger posed by the perceived input. Someone who loves cats would undoubtedly experience a warm fuzzy feeling, whereas a person with a cat phobia would be panicked, resulting in dramatic and measurable changes in heart rate, respiration, and eccrine activity (skin sweating).

An evolutionary motivation baked in to our consciousness is the “fight or flight” response, in which we respond to danger and make a quick decision whether to run or defend ourselves. We all have different thresholds for which input might trigger this response. The line is often blurred between what constitutes actual danger or a seemingly innocuous sensory event that ignites an unpleasant memory or triggers the ghost of a previous traumatic experience.

Now that we have briefly explored a thumbnail sketch of psychophysiology, what kind of equipment is used for recording psychophysiological data? When we set up a psychophysiology experiment, we can record the changes occurring in the body and analyze the results with a great depth of accuracy. To record these signals, specific data acquisition hardware such as the BIOPAC MP36 is commonly used, with a SS2L transducer for recording ECG and a SS57L EDA (electrodermal activity) transducer. The software used to process and display these signals is very often AcqKnowledge (for research) or Biopac Student Lab (for education).

Although emotions cannot be captured or studied in a lab, the physiological changes that result from emotional experiences certainly can be.

For further reading about emotional affect, please see our blog “Circumplex Model of Affect and Motivational State.”

Other related BIOPAC resources:

BIOPAC offers a wide array of wired and wireless equipment that can be used in your research. To find more information on solutions for recording and analyzing signals such as ECG, heart rate, respiration, and more using any platforms mentioned in this blog post, you can visit the individual application pages on the BIOPAC website.

Photo by Noah Buscher on Unsplash


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