Using Physiology in Psychology and Social Sciences

There is a particular motivation to use psychophysiology in psychology, but is there the same enthusiasm for sociology? The method of measuring endocrine and peripheral neurophysiological responses for social psychologists and the ability to obtain answers continuously, covertly, and online. Online means that researchers do not have to rely on inferences based on prospective or retrospective self-reports. Furthermore, the temporal topology of a physiological response. Moreover, covert generally ensures that research participants do not monitor and adjust their responses. Physiological responses are more sensitive, uncensored, predictive, and mechanistic. Also, they can be susceptible to changes in mental states that individuals cannot report.

Unlike Likert-type self-report scales that force a ceiling or floor on measurements, they cover broad ranges of values. Nevertheless, physiology might be too reductive to catch all the nuances of introspective questions about their feelings, intentions, and thoughts.

Even though a reductionist critique is that blood pressure responses, like most ANS responses, are imperfect measures and are often end-points of complex physiological processes that are difficult to measure directly. So, although pointing to physiological responses as statistical mediators between a personality trait on the one hand and end-points of health or behavior, on the other hand, is a potentially fruitful avenue of study, one needs to be careful not to over-state mechanism claims.

Nevertheless, ANS responses can be more sensitive indicators of psychological processes than explicit self-reported states.

Physiological indexes

Many fallacies prevent the usage of physiology in psychology.

Consequent fallacy the form “A difference in physiological response X occurs when independent psychological variable Y is manipulated.” For example, the basis of an observation that a person’s heart rate increased when they viewed photographs of another person as opposed to a non-sentient object might have led an investigator to conclude that such heart rate rises measured passion or even love.

Validity fallacy and The validity problems with this approach were at least twofold: it relied on a relatively naive physiological assumption, and researchers fell into the logical “reverse inference” or “affirmation of the consequent” trap. The former was somewhat excusable as the assumptions of parallel sympathetic anabolic processes (i.e., activation of one process indicated activation of all) and catabolic tension between sympathetic and parasympathetic functions (i.e., the latter tending to diminish the former) were regarded more as fact than hypothetical. However, “affirmation of the consequent” is inexcusable as a supposed physiological response (i.e., consequence) does not guarantee the presence of a psychological phenomenon except in minimal and unique circumstances.

The nature of relationships between any measures or indexes, whether physiological, behavioral, or subjective, of psychological states and processes and the conditions and processes themselves, always bear scrutiny. Problems of reverse inference or affirmation of the consequent are not distinctive to physiological indexes, for example, from methodological concerns about social desirability problems with paper and pencil measures. However, it is essential to remember that there is no validation shortcut just because indexes may be physiological.

Embodiment of physiology

All psychological processes are somehow embodied: the taxonomy of relationships between psychological and physiological variables assuming the identity thesis. Blascovich (2000) summarized their arguments as “... the more one limits the social psychological construct, and expands the set of physiological measures indexing it, the closer the construct and index can come to an invariant relationship;” that is, one cannot occur without the other.

Physiology can be considered on three dimensions or axes. These include generality, specificity, and sensitivity.

Generality refers to a contextual continuum on which indexes vary from limited or “context-dependent” to unlimited or “context-free.” The latter is more desirable because the physiological indexes are generalizable across all situations (i.e., contexts).

Specificity involves the relationship between the index and construct. Perfect specificity means a one-to-one relationship between a construct and its index. The index is activated when the construct is activated, and vice versa. The index is inactive when the construct is inactive, and vice versa. In Cacioppo et al.’s (2007) terminology, specificity varies from “one-to-one” to “many-to-one.” The latter means that any of several constructs can lead to the same index and, therefore, cannot be distinguished via that index.

Sensitivity in the typology of Cacioppo et al. (2007) is the degree to which the physiological index corresponds to the putative underlying psychological state or process. Sensitivity provides information about the degree to which changes in the physiological index reflect the changes in the underlying psychological condition or procedure.

Principals of using psychophysiology in social sciences

Principle 1: Specify the nature of the construct Because social psychological constructs are often labeled with common language terms (e.g., attitude, self-esteem, risk-taking, ego depletion, threat, stress, liking, prejudice), sometimes researchers assume that everyone agrees on what a construct means. Indeed, the reverse is true. Because social psychological constructs are often labeled in ordinary language terms, their meaning is often left implicit, fuzzy, or both.

Principle 2: Specification of physiological indexes Nevertheless, we are concerned with peripheral physiological and endocrine processes as candidate indexes for social psychological constructs.

Principle 3: Specification of theoretical physiological linkages Physiology is formed by theory. In many ways, the power of the physiological index rests on the validity of the underlying theoretical rationale. Because of the importance of establishing one-to-one relationships between physiological indexes and psychological constructs, and because very few, if any, peripheral physiological responses are not mediated or moderated by a cascade of other physiological factors, it is very likely that worthwhile indexes can only increase in specificity and sensitivity if they include multiple responses and, often, are measured over time.

Polyvagal theory and social interaction

One theory that has received much attention regarding the inferences one can draw from heart rate variability is Porges’ polyvagal theory (e.g., Porges, 2007). In this theory, Porges argues that vagal regulation stemming from the nucleus ambiguous and enervation from cranial nerve X acts on the vagus nerve to modulate the heart period. The polyvagal theory further specifies that primates uniquely have vagal nerve modulation (see Grossman & Taylor, 2007), which has evolved as part of the social engagement system. One of the primary postulates of polyvagal theory is that social factors (affiliation, social engagement) or personality factors (optimism, bonding, compassion) can modulate vagal activity. Specifically, Porges argues that higher RSA (high cardiac vagal tone) can be used as an index of adaptive emotional regulation and responsiveness to the social environment. Similarly, cardiac vagal reactivity might also index appropriate social engagement in that increased vagal reactivity might be associated with calmness, tranquility, and a lack of distress.


However, the nature of the social context adds some complexity to these effects. Indeed, in highly stressful situations or tasks that require mental attention or effort, one should expect a withdrawal of the vagal brake (resulting in lower RSA). Cognitive psychophysiologists have used decreases in RSA as an index of attention or mental effort (Tattersall & Hockey, 1995).

RSA (RSA reactivity) changes have been implicated as a possible mediator for why implicit goal-setting might improve performance.


I argue that future physiology applications in psychology and social sciences will focus on the vagal tone and valence as the primary physiological index with a greater possibility of explaining the observed effects. Applications of cardiac vagal tone and vagal reactivity are increasing in personality and social psychology. Some applications have focused on how dispositional emotional styles are linked with cardiac vagal tone (Demaree & Everhart, 2004; Oveis, Cohen, Gruber, Shiota, Haidt, & Keltner, 2009; Sloan, Bagiella, & Shapiro, 2001). For example, individuals with more significant hostile tendencies have a lower cardiac vagal tone at baseline, during an emotional induction task, and at recovery than those lower in hostile tendencies (Demaree & Everhart, 2004; Sloan et al., 2001). Similarly, but on the brighter side, Oveis and colleagues found that those higher in optimism had a higher vagal tone. Evidence suggests that vagal tone might be a reasonable physiological response to index general positive and negative affect.


Blascovich, J., Vanman, E., Mendes, W., & Dickerson, S. (2014). Social Psychophysiology for Social and Personality Psychology. In Social Psychophysiology for Social and Personality Psychology (1st ed.). Sage Publications.

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