Date of Award

Summer 2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Program

Clinical Psychology

First Advisor

Nielson, Kristy A.

Second Advisor

Gordon, Nakia

Third Advisor

Hoelzle, James

Abstract

Alexithymia is a stable personality trait typified by externally oriented thinking and difficulties identifying and describing feelings. It is associated with cognitive-affective deficits such as poorer memory for emotional and neutral information as well as executive dysfunction. Relatedly, aging is accompanied by executive dysfunction and increasing alexithymia. Because executive functions comprise multiple cognitive skills, it is essential to demarcate which are impacted by aging and alexithymia. While age-related deficits in inhibitory control are well established, there is a dearth of literature examining inhibition in alexithymia. Thus, this study aimed to examine the effect of alexithymia on inhibition and to interrogate its potential additive impact to aging effects.Participants were 538 undergraduate students (age = 18-35) and 201 middle-aged to older adults (age = 48-92). All completed the 20-item Toronto Alexithymia Scale (TAS-20) and go, no-go, and stop-signal tasks. Following removal of participants with missing data or invalid task performance, the final sample included 384 younger and 81 older adults. Separate hierarchical regressions predicting accuracy and reaction time were examined. Post hoc models included TAS-20 subscores. Exploratory moderation and mediation models were also conducted to interrogate shared variance among covariates and predictor variables.Female sex and greater age predicted slower reaction times across all three tasks. Older age was also associated with less accurate responding to target and inhibition trials on no-go and slower and less accurate inhibition on stop. Alexithymia predicted poorer inhibition on no-go and stop via difficulty identifying feelings (DIF). Mood symptoms neither moderated nor mediated the relationship between DIF and inhibitory control.These results replicate the age-related tradeoff of speed for accuracy in reaction time and inhibition tasks. They also provide novel evidence for alexithymia deficits in non-emotive inhibitory control. The impact of DIF on both automatic (no-go) and conscious (stop) inhibitory control supports processing theories of alexithymia. In particular, DIF contributed to poorer extrinsically and intrinsically cued response suppression. Thus, top-down and bottom-up information processing may be disrupted in alexithymia. Critically, the alexithymia effects were additive to age effects extending support for alexithymia as a risk factor for cognitive aging.

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