Dorien Bangma

FDM AND NORMAL AGING | 41 informed about the study via word-of-mouth, email or social media). Eleven participants with evidence for psychiatric or neurological conditions were excluded: five participants showed high scores on a depression rating scale (Beck Depression Inventory-II-NL > 19; Roelofs et al., 2013), two participants obtained low scores on a dementia rating scale (Mini Mental State Examination < 24; Folstein et al., 1975) and four participants reported having a neurological or psychiatric condition which might have a negative impact on cognition (e.g., brain tumor and Lyme disease). The remaining 180 participants (sample 1) were on average 49.58 years old (range 18 – 87 years; Table 3.1) and obtained on average 15.15 years of education. Slightly more females (57.2%) than males were included in sample 1 (Table 3.1). Participants – sample 2 A second sample (n = 124) was included to evaluate the external validity of possible age effects. The recruitment procedure (i.e., via contacts of the researchers, recruited by word-of-mouth, e- mail or social media) as well as the inclusion and exclusion criteria (e.g., no evidence for a psychiatric or neurological condition) were similar to the first sample. None of the participants in sample 1 were also included to sample 2. Both samples were comparable with regard to the age range. However, the average age of the second sample was significantly lower than in the first sample (Table 3.1). Furthermore, the second sample obtained on average two more years of education than the first sample. The samples did not differ significantly on other demographic characteristics (Table 3.1). Ethics statement The Ethical Committee Psychology of the University of Groningen, Groningen, The Netherlands, and the Medical Ethical Committee of the University Medical Center Groningen, Groningen, The Netherlands, approved this study. Participants were informed about the content of the research prior to assessment. Furthermore, they were informed that participation was Table 3.1. Demographic characteristics of samples 1 and 2. Sample 1 Sample 2 Group differences (p-value) n 180 124 Age range 18 - 87 19 - 87 Age M(SD) 49.58 (18.37) 41.28 (17.73) < .001 a Age groups < .001 b < 30 20.6 % 37.9 % 30 – 39 12.2 % 14.5 % 40 – 49 11.1 % 5.6 % 50 – 59 22.2 % 27.4 % 60 – 69 21.7 % 7.3 % > 70 12.2 % 7.3 % Female 57.2 % 58.9 % .775 c Education M(SD) 15.15 (3.78) 17.04 (3.60) < .001 a In employment 61.1 % 67.7 % .237 c Income range 25.000 – 35.000 25.000 – 35.000 .198 b Note. Age and education in years. Average annual gross income range in Euro. a One-way ANOVA, b Mann-Whitney U test, or c Pearson’s chi-square tests.