The evidence - affect and eudaimonia measures
Although there is an emerging trend towards 11-point scales for life evaluations, in the affect literature many authors still rely on 5-point measures, particularly in the case of experienced affect (e.g. Diener et al., 2009). Eudaimonia scales also tend to have fewer response categories (typically 5 or 7). Because the majority of existing affect and eudaimonia measures contain multiple items in order to assess each hypothesised underlying construct (e.g. 5 items to measure positive affect; 5 items to measure negative affect) and responses are then summed across a variety of items, overall scale sensitivity may be less severely threatened by a smaller number of response options, relative to single-item measures. But more work is needed to examine this further.
Another possible reason for the predominance of shorter scales in this literature may be that, while it might be relatively straightforward to assign reasonable verbal labels to a 5-point scale (e.g. never, rarely, sometimes, often, always; strongly agree, agree, neither agree nor disagree, agree, strongly agree), devising seven or more verbal categories strays into vague terms that do not have a clearly accepted position (e.g. quite often; slightly agree). One obvious solution to this challenge is to adopt numerical scales (e.g. 0-10) where only the scale end-points are labelled (e.g. from “never” to “all the time” or “not at all” to “completely”); this is the approach that has been adopted by the UK’s ONS (2011b) in their experimental measures of subjective well-being. Further development of such scales could helpfully examine whether respondents are actually able to make meaningful discriminations between eleven different response categories when it comes to reporting affective experiences and eudaimonia.