Measuring Personality Systems in Older Adults: Age-Neutrality of the Dutch BIS/BAS Questionnaire.

INTRODUCTION

With a rapidly aging population, age-neutrality of psychological instruments is becoming ever more important for accurate assessment of older adults. This study aims to test the age-neutrality of the Dutch Behavioral Inhibition System/Behavioral Approach System (BIS/BAS) scales by means of Differential Item Functioning (DIF) and Differential Test Functioning (DTF) analyses.

METHODS

DIF and DTF analyses were conducted using an odds ratio approach. Potential DIF was examined for the two primary scales and three BAS subscales in 390 Dutch-speaking participants divided over three age groups.

RESULTS

Overall, the BIS-BAS scales lacked age-neutrality when comparing older adults to young adults: eight out of 20 items (ie, 40%) displayed DIF according to the adjusted Bonferroni corrected cut-offs, which exceeds the threshold of 25% for large DIF. Thus, for 40% of the test items, items were differently endorsed by young and older adults with the same position on the construct measured by the item. Therefore, the implications of the item-level DIF on the scale level were investigated across age groups. DTF analyses revealed large DTF for all BIS and BAS scales according to the adjusted Bonferroni corrected cut-offs.

DISCUSSION

DIF found in items on the BIS scale and BAS-Drive and BAS-Fun Seeking scale can probably be explained by a difference in degree of expression across age groups. A solution could be the development of age-specific norms. DIF on BAS-Reward Responsiveness subscale could be partly due to measuring a different construct across age groups. Rephrasing or replacing such items with DIF may increase age-neutrality of the BIS/BAS Scales.