Middle response functioning in Likert-responses to personality items

Two studies examined whether the middle response option in graphic rating scales indicates a moderate standing on a trait/item, or rather a dumping ground for unsure or non-applicable (N/A) responses. Study One identified middle response-option dysfunction. Study Two indicated that respondents use the middle response option as an N/A proxy, even under implicit 'skip if you do not know' instructional sets. Although middle response category 'misuse' did not adversely affect reliability and validity in these studies, it is recommended that assessment developers (especially in on-line administration contexts) regularly include an N/A response option when administering graphic rating scales.