“Do you ever look at someone and wonder what is going on inside their head?”
Joy, an anthropomorphized manifestation of happiness, delivers this line at the opening of Pixar’s 2015 animated hit “Inside Out,” a film that explores the emotional struggles of its young protagonist. She could have been speaking for generations of researchers who have plumbed the depths of the human psyche for a better understanding of the mechanisms behind our feelings, moods, and emotions.
When today’s researchers talk about emotion, they typically do so in terms of affect, the underlying physiological and psychological experience of feelings and emotions as a reaction to stimuli. Affect and emotion are not the same thing, per se, but are fundamentally connected. While the feelings we describe as fear, joy, love, hate, etc. remain abstract, affect is more concrete. BIOPAC co-founder and head of R&D describes it as “the measurable quality or manifestation of emotion in the human body.”
This manifestation can be measured in the human nervous system’s response to stimuli. Depending on the nature of the stimuli and how this sensory data is interpreted by the central nervous system, an array of physiological responses can take place: heart rate changes, the stomach and muscle groups tense, skin temperature responds, triggering sweat glands, among others.
The signals corresponding to these reactions provide researchers with valuable data to help them better understand affect and emotion. These signals—electroencephalogram (EEG), electrodermal activity (EDA), electromyogram (EMG), heart rate, and respiratory rate, to name a few—can be recorded and measured using a range of currently available sensing technologies.
As an example, a 2019 study published through the Queensland University of Technology used respiration signals as a means of classification for human emotions such as happiness, sadness, surprise, disgust, fear, and anger. In the study, breathing signals, including airflow rate and volume, were acquired and recorded using a BIOPAC MP36 data acquisition unit while participants were shown seven film clips, each associated with a different emotion. The study concluded that the respiratory data was 80% effective in accurately classifying affective responses to the film stimuli.
A team of researchers at the Khwaja Fareed University of Engineering and Information Technology in Pakistan took their investigation into the connection between physiological signals and emotion a step further. They used a similar approach by measuring participant response to movie clips, however this time, four types of physiological signals were acquired, including ECG, EMG, respiration, and skin conductivity (SC). The data was acquired with a wide range of signal sensors and analyzed via a BIOPAC MP160 DAQ System.
Signal sensing technology also allows researchers to study emotion in multiple participants simultaneously, as was the case in a 2020 dyadic study of how a parent’s stress and emotional suppression affects their children. The study measured physiological responses of both parents and children using ECG and impedance cardiography (ICG) via a BIOPAC MP150 data acquisition unit.
The mysteries of human emotion are being unlocked through a growing understanding of the affective response to stimuli. For more information on how physiological signals can be gathered and analyzed for this purpose, see our app note on emotional state physiology as well as our webinar Emotion and Objective Physiological Measures.
Contact BIOPAC for the latest information on how we can help you measure affect in the lab.