Interpretation of the Middle Anchor of Likert Scale
There has been substantial debate about using an even or odd number of rating scale points in attitude scaling with surveys. When an odd-numbered rating scale is used, researchers are confronted with an issue: how to label the mid-point. Not surprisingly, research on interpretation of the middle option finds a lack of consistency regarding respondent interpretation of the midpoint (Baka, Figgou, & Triga, 2012; Kalton, Roberts & Holt, 1980; Nadler, Weston, & Voyles, 2015). When respondents were allowed to choose the label they associated with a rating scale mid-point, different labels were used for items assessing attitudes towards capital punishment and Sunday observance, suggesting different meanings for the middle response category as a function of item content. Nadler et al. (2015) found interpretation of the mid-point as “don’t care,” “no opinion,” “unsure,” “neutral,” “equal/both,” and “neither” was found with a sample of U.S. undergraduates asked about politics in the U.S. Baka et al. (2012) found the mid-point was interpreted as lacking in knowledge or indifferent, ambivalent, disputing aspects of the question, or had no information on the topic. When respondents choose the mid-point as their response, it is possible the respondents are telling us that they do not have a response because they either have no opinion, are unclear/uncertain what their opinions are, or don’t care; that they do have a response and the response is that they have an opinion that is moderate in intensity, or they do not understand the question, or have no information about the topic. In sum, the question is: are the mid-point Likert scale responses substantive or non-substantive?
In attitude scaling, if respondents have access to the necessary information and neither agree nor disagree with the issues and they choose the mid-point anchor to indicate their state of mind, the response is a substantive response and it should be coded and add to the composite scale score. On the other hand, a non-substantive response is a response that does not contribute or add to the measurement of the target attitude. However, the meaning of a non-substantive response is unclear, as it is multifaceted and could indicate carelessness, confusion, or intentional behavior (Francis & Busch, 1975). A non-substantive response can be a DK response implying that respondents cannot retrieve the relevant information from their long-term memory because they either do not have that information or cannot retrieve the information at the time to form an opinion. Alternatively, a non-substantive response is a random response if respondents guess because they do not understand the question or if they simply satisfice because they do not wish to spend the effort to provide a thoughtful response. It can also be a systematic but irrelevant response, due to deliberate efforts to present a certain impression or to some unconscious stable response style such as leniency, neutrality, or an acquiescent response tendency.