physiological responses, even in experiments that are not related to emotional
responses (Schandry et al. 1993 ).
The advent of functional MRI (fMRI) has permitted illumination of physiolog-
ical processes occurring in the brain of living humans. Studies of neural activation
patterns have discerned significant relations between certain patterns and specific
emotions elicited from social cues. These cues are based on verbal, facial, or
postural stimuli (Peelen et al. 2010 ) and from reactions to evocative photographs
(Baucom et al. 2012 ). For example, method actors with experience in quickly
changing the expression of emotions were asked to prepare mental scenarios that
encapsulated certain affective language such as anger, lust, and disgust. The fMRI
detected patterns associated with valence (positive or negative), lust, arousal, and
sociality when the actors were asked to experience given emotions on cue (Kassam
et al. 2013 ). These studies do not examine emotional experiences in normal, daily
activities and thus are limited in applicability; however, they demonstrate that
“invisible”emotions can be made visible in a new way.
The debate over peripheral versus central determination of emotions can also
lead to the question of just where the peripheral physiological changes originate.
Are these local responses, or are they mediated by the central nervous system?
Stress responses, for example, can be local (leading to inflammatory reactions in
local tissues) or general (originating from cognitive processes in the brain) (Brown
2016 ). The latter produces the general stress response, which can be interpreted as
anxiety, again in the brain. Thus, at least some emotions involve feedback between
central and peripheral processes.
Not all experiences are directly that of emotions, although many human expe-
riences elicit emotional responses. Pain, for instance, is an intense experience that
may elicit an emotional response, but pain is an experience that is of considerable
interest in and of itself. How do we understand the level of another person’s pain?
In fact, the common method is to simply ask people to rate their pain on some scale
(e.g., one to ten). This method has some drawbacks, because people may differ both
in ideas about what is acceptable to report about one’s pain and in experience with
pain at various intensities. Individuals may have a truncated scale for whether to
report pain and, if they do, at what intensity. Thus, a given stimulus can elicit varied
reports of pain levels, and it is difficult to disentangle what differences exist in pain
experience versus what is reported. It is only with the advent of research using
fMRI that some degree of accuracy in assessing pain intensity in an objective
fashion has been achieved (Wager et al. 2013 ). As in studies of emotions, use of
fMRI in pain research has limitations, with only laboratory-based as opposed to
everyday experiences capable of being studied. Moreover, pain is a multidimen-
sional experience, encompassing more than a ranking of severity at a moment in
time (Heft and Robinson 2016 ).
Tiredness and fatigue due to poor sleep are other experiences that are not always
visible to an outside observer. Much research in this area has relied on self-reports
to elicit information about both sleep quantity and sleep quality. Objective measures
such as polysomnography are also available, allowing assessment of sleep quantity
and aspects of sleep quality. However, there are some aspects of sleep quality that
1 Making Visible the Invisible 5