Jun
14

Major Key: Electrodermal Activity (EDA)

Hello, everyone! Things are getting off the ground already and going very well. One of the main things I have been working on recently is learning the techniques of electrodermal activity (EDA) analysis. Since EDA (also known as galvanic skin response or skin conductance response) is so important to my thesis, I will use this post to accomplish two goals.

  • Explain why psychophysiological measures are important
  • Explain what EDA is
  • Demonstrate EDA’s importance in psychological research

 

Psychological states are real, but designing objective measures of those states can be challenging. This is why objective, psychophysiological measures have so much appeal. In most cases, humans exert no conscious control over their physiological states, such as rate of breathing, skin temperature, or sweating. These processes tend to be automatic. An automatic measure has a level of objectivity which can be useful to avoid biases which could plague self-report measures.

 

But it is not enough to just avoid a bias caused by self-report measures. In order to be useful, a given measure must be associated with some psychological state or neurological response. It is currently accepted that changes in electroodermal activity, that is, changes in the electrical conductivity of the skin, reflect increases or decreases in a human’s physiological arousal. We are confident of this because sweating is controlled by the sympathetic nervous system which underlies the “fight or flight” response. So, if the autonomic nervous system is active, sweating increases which will result in increases in skin conductance. Although EDA strictly measures arousal, the context may allow us to infer an individual’s emotional state. In a threat conditioning procedure, for example, we may infer that increases in EDA reflect fear, or an anticipation of an aversive stimulus. In this way, EDA can be used as a measure of learning because those who learn that a conditioned stimulus (neutral stimulus) predicts the onset of an unconditioned stimulus should evince higher levels of EDA, measured in microsiemens (µS). Typically, EDA is measured through electrodes placed on the middle or distal phalanges of a participant’s non-dominant hand.

 

skin conductance

 

EDA has proven valuable in the investigation of various questions related to psychopathy, in particular. EDA may offer us valuable information about the likelihood of an individual to display aggressive antisocial behavior later in life. In one longitudinal study (Gao, Raine, Venables, Dawson, & Mednick, 2010), children went through a threat conditioning procedure at ages 3, 4, 5, 6, and 8 years while their skin conductance was measured. These children were also rated by their teachers on antisocial behavior, anxiety/fearfulness, and hyperactivity-inattention. The researchers’ main finding was that poor electrodermal fear conditioning from ages 3 to 8 years was associated with aggressive antisocial behavior at age 8 years. In other words, fluctuations in EDA in a threat conditioning procedure may have predictive value as this study shows that it correlates with aggressive antisocial behavior later in life.

 

Thanks for reading! I welcome your questions/comments.

 

References:

Gao, Y., Raine, A., Venables, P.H., Dawson, M. E., & Mednick, S. A. (2010). Reduced electrodermal fear conditioning from ages 3 to 8 years is associated with aggressive behavior at age 8 years. The Journal of Child Psychology and Psychiatry 51(5). 550-558.

Comments

  1. alexanderwilliams says:

    Glad to hear of your interest, Matt! At least currently, there isn’t a formal plan for dealing with possible nervous system “contamination” that may take place. EDA is imperfect, which is why you’ll sometimes see fear-potentiated startle used as a measure of fear. Researchers have claimed that this technique is less influenced by cognitive factors, compared to EDA.

    On a related note, there are certain individuals who can be ruled out if their data are irregular. For example, about 10% of people are non-responders, meaning that they have very low (less than 1 microsiemen) skin conductance responses which do not fluctuate in response to aversive stimuli. These participants won’t be included in analyses.

    Looking forward to providing you more updates!

  2. Matt McGuinness says:

    Informative post Alex! Can’t wait to see how you use EDA in your project on fear and empathy. Very interesting the way the technique is utilizing the separations between somatic and autonomic nervous systems to analyze emotional responses. I’m curious as to how you’ll approach the separation of the nervous systems in your project, especially with the participants experiencing fear through these objects and whether something in their somatic nervous system might end up influencing your EDA results if they have time to think about the situation they’re in. Looking forward to hearing more about your project!