Undergraduate Honors Theses

Thesis Defended

Spring 2018

Document Type


Type of Thesis

Departmental Honors


Psychology & Neuroscience

First Advisor

Dr. Naomi Friedman

Second Advisor

Dr. Mark Whisman

Third Advisor

Dr. Olivia Miller


Rumination is a process of repetitive negative thoughts believed to maintain symptoms of depression. Mixed literature indicated a potentially unique association between rumination and intelligence masked by the frequent focus on depression. The present study extended previous research by controlling depression, examining ruminative subtypes (reflection and brooding), and intelligence subtypes (verbal and performance). Participants were 751 individual twins, 351 monozygotic and 400 dizygotic, recruited from the Colorado Longitudinal Twin Study. Primary data were collected at age 23. Rumination was measured by the Ruminative Response Scale’s reflection and brooding subscales, and intelligence was measured using Raven’s Advanced Progressive Matrices (RPM). Depression symptoms were measured by both the Center for Epidemiological Studies –Depression Scale, and the Diagnostic Interview Schedule-IV. Data collected at age 16 from the Wechsler Adult Intelligence Scale were used to evaluate verbal and performance IQ. Primary findings indicated that RPM had a significant positive association with reflection, whereas brooding had a negative and marginally significant association. After controlling for depression, although the association between reflection and RPM remained statistically significant and positive, the marginal negative association between brooding and RPM was not significant. Differences also emerged between reflection and brooding with intelligence types: verbal and performance. These results suggest brooding may not have a significant relationship with intelligence when controlling for shared variance with depression. The finding that subtypes of rumination have unique associations with IQ subtests suggests the need to look at rumination as a multifaceted construct in future research.