This study examined whether responding to many items increased middle category response. In two internet-based experiments, respondents were randomly assigned to one of the four versions of the questionnaire. In Study 1, the respondents completed a Big Five questionnaire that had varied item arrangements. The results showed that the endorsement of the middle category increased for items placed later in the questionnaire for all versions. In Study 2, the Big Five questionnaires differed in that all items were administered at once or were facially divided into two scales. The results indicated that less middle categories were selected in the first 5 items of the second half scale than in the last 5 items of the first half scale for the divided formats, but the endorsement rates increased for items placed later toward the end of both half scales. An increasing middle category response was also found for another scale. Therefore, this phenomenon seems reliable.
