Psychological Rigidity in Eating Disorders: Rigid Dietary Control and Cognitive Rigidity

Abstract

A broad range of psychological rigidity has been observed and studied in relations to eating disorders. However, studies have neglected to use measurements that are diet- and food-specific when studying problems of rigidity in eating and weight-related disorders. The current study aims to investigate two types of rigidity – rigid dietary control and cognitive rigidity – in relations to disordered eating symptoms using both self-reports and experimental tasks that are specifically diet and food related.

In study 1, the Flexible and Rigid Control scale (Westenhoefer, Stunkard, & Pudel, 1999) which distinguishes flexible dietary restraint from rigid dietary restraint was translated and validated. The scales factor structure, psychometric properties, and the differential relationship of the two types of dietary control and the psychological, behavioral, emotional symptoms of eating disorders were investigated. Participants were 305 female university students who were on a diet. Results indicated that the Korean version of the Flexible and Rigid Control scale was best modeled to have a two factor structure with 11 and 13 items loading to Flexible Control and Rigid Control respectively. Consistent with previous research, the two subscales demonstrated concurrent and construct validity, and evidence for the separation of two constructs were found.

In light of previous research that linked cognitive rigidity with eating disorders, in study 2 the Food Picture Set-shifting Task (FPST) was developed to measure difficulties in set-shifting regarding calorie related rules and food pictures. A total of 89 female university students were recruited and assigned to three groups based on their dieting status and levels of eating disorder symptoms (32 low risk dieters

29 high risk dieters

29 non-dieters). The FPST, Wisconsin Card Sorting Test (WCST), self-report questionnaires on dietary restraint, and clinical variables were assessed. Results showed that the FPST is a valid measure of set-shifting abilities. Although dieters and non-dieters did not differ in the overall FPST performances, dieters showed higher perseveration error in calorie to color shift than non-dieters. Intent to diet (dieting status) was more associated with food-specific set-shifting impairments while actual dietary restraint (EDEQ) was related to general set-shifting impairments as measured by WCST. The results suggest that the FPST can be a unique and useful tool in detecting cognitive rigidity related to food and may provide insight on the neuropsychological difficulties of maintaining a healthy diet.

The current study validated two diet- and food-specific rigidity measurement tools – the Korean version of the Flexible and Rigid Control scale and the Food Picture Set-shifting Task – and explored the relationships between rigidity and eating disorders. Consistent with previous research, the findings from the present study suggest that dietary restraint is not a homogenous construct and that intent to restrain and actual behavioral restraint may affect cognitive rigidity through different mechanisms. Limitations as well as suggestions for future research are discussed.