Alexithymia

Literally “no words for feelings” — a stable trait of reduced ability to identify and describe one’s own emotional states, and to distinguish emotions from the bodily sensations that accompany them. Quadt et al. (2018) give it a load-bearing role: it is repeatedly the variable that, once controlled, explains away interoceptive deficits credited to other conditions.

The confound that keeps reappearing

The pattern the review documents:

• Autism. Autistic adults show reduced heartbeat-tracking accuracy — but at least one study (Shah et al. 2016) finds the deficit tracks alexithymia, which is highly comorbid with autism, rather than autism per se. On this reading the emotion-processing deficits of autism, characterized by high alexithymia, may be the principal driver of its interoceptive impairment. A recent study links impaired interoceptive awareness (not sensitivity) to autistic traits, alexithymia, and empathy together (Mul et al. 2018).
• Non-autistic populations. High alexithymia is associated with impaired interoceptive accuracy independent of autism (Brewer, Cook & Bird 2016), whose title states the strong form: alexithymia as “a general deficit of interoception.”
• Eating disorders. Alexithymia (with depression and anxiety) is a comorbidity that ED interoception studies “often do not take into account”; one bulimia study found the apparent accuracy deficit vanished once comorbid alexithymia, depression and anxiety were covaried out.

The methodological lesson the review draws is that a great deal of “condition X impairs interoception” may be “alexithymia impairs interoception, and alexithymia rides along with condition X.” Whether the interoceptive deficit is primary to alexithymia or a shared cause is the open form of the claim.

Why it matters theoretically

If emotions are, per construction and interoceptive inference, categorizations built on interoceptive signals, then a person who cannot read their bodily signals well should struggle to identify their emotions — which is exactly the alexithymic profile. Alexithymia is thus a natural test case for the interoception→emotion link: the Brewer/Bird claim that alexithymia is fundamentally an interoceptive deficit is the constructionist prediction stated as a personality trait. It also connects to empathy: reduced capacity to read one’s own affect co-occurs with reduced reading of others’, consistent with the perception-action model in which empathy re-uses self-directed interoceptive machinery.

Placement in the wiki

Alexithymia had been mentioned unhosted on interoceptive-trait-prediction-error (as a complication — atypical interoception tracking alexithymia rather than autism, without directly testing ITPE) and on interoceptive-psychopathology (as an uncontrolled comorbidity). It now has a home as a transdiagnostic interoceptive-deficit construct. It is held at one remove: the primary alexithymia sources (Shah, Brewer, Bird; Berthoz; the Toronto Alexithymia Scale literature) are not in raw/, so the wiki carries the construct through Quadt et al.’s review, not first-hand. The unresolved question — is alexithymia the cause of these interoceptive deficits, a label for them, or a correlated third thing — is the same cause-or-consequence problem that runs through interoceptive-psychopathology.