Dorien Bangma

164 | CHAPTER 7 €100 in one week, a score of 75% was given. Finally, an average total score is calculated for all scenarios, which has been found to have an excellent internal consistency in the present study (Cronbach’s α = .97). The Impulsive Buying Questionnaire (IBQ) was used to evaluate the impulsive buying tendency (Beatty & Ferrell, 1998; Coley & Burgess, 2003; Rook, 1987; Verplanken & Herabadi, 2001). The questionnaire contains 31 questions about impulsive buying behavior scored with a four-point scale from ‘strongly disagree’ to ‘strongly agree’ and assesses three components of impulsive buying, i.e., ‘cognitive component’ (15 questions), ‘affective component’ (12 questions) and ‘situational component’ (4 questions). The internal consistency of the ‘cognitive component’ and ‘affective component’ was found to be good (Cronbach’s α = .82 and .82, respectively). However, the internal consistency of the ‘situational component’ was low (Cronbach’s α = .07). The total score (range 27 – 108; Cronbach’s α = .89), which is calculated by adding up the scores on the cognitive and affective component, reflects an individual’s overall impulsive buying tendency with higher scores indicating a stronger tendency to buy on impulse. Finally, the Iowa Gambling Task (IGT; Bechara et al., 1994; Grasman & Wagenmakers, 2005) was included in the test battery. According to a review of Buelow and Suhr (2009) the IGT is considered to be a measure of affective or emotional decision-making . Using a computerized version of the IGT, participants have to choose 100 times between disadvantageous (A and B) and advantageous (C and D) decks that are associated with certain gains and losses of money. Participants receive a hypothetical startup capital of €2000 and are asked to make decisions as it concerns their own money. Participants are not informed, however, about which deck results in relatively high gains or losses; they therefore have to learn from trial and error. A total net score over 100 trials is calculated, i.e., number of times the advantageous decks were chosen minus the number of times the disadvantageous decks were chosen. Cognitive functioning. The Cognitive Functions ADHD test battery (CFADHD; Tucha et al., 2014) of the Vienna Test System (Schuhfried, 2013) assesses cognitive functions in which adults with ADHD have been shown to present difficulties and was used in the present study to explore the association between cognitive impairments and FDM. Nine cognitive functions were examined, i.e., information processing speed (Trail Making Test – part A (TMT-A)), vigilance and selective attention (Perception and Attention Functions test: Vigilance and Selective Attention (WAFV and WAFS, respectively)), inhibition (response inhibition go/no- go task (INHIB)), interference (Stroop interference test (STROOP)), figural fluency (5-Point Test (5POINT)), cognitive flexibility (Trail Making Test – part B (TMT-B)), task switching (Task switching test (SWITCH)) and verbal working memory (N-Back Verbal test (NBV)). In addition to the CFADHD, the Arithmetic subtest of the Wechsler Adult Intelligence Scale IV (WAIS-IV Arithmetic; Wechsler, 2008; Wechsler, 2012) was included to assess numeracy .