What are the consequences of including a “don't know” (DK) response option to attitudinal survey questions? Existing research, based on traditional survey modes, argues that it reduces the effective sample size without improving the quality of responses. We contend that it can have important effects not only on estimates of aggregate public opinion, but also on estimates of opinion differences between subgroups of the population who have different levels of political information. Through a pre-registered online survey experiment conducted in the United States, we find that the DK response option has consequences for opinion estimates in the present day, where most organizations rely on online panels, but mainly for respondents with low levels of political information and on low salience issues. These findings imply that the exclusion of a DK option can matter, with implications for assessments of preference differences and our understanding of their impacts on politics and policy.

Words used to describe emotion are influenced by experience, context and culture; nevertheless, research studies often constrain participant response options. We explored the influence of response options on how people conceptualise emotion words in two cross-sectional studies. In Study 1 participants rated the degree to which a large set of emotion words (n = 497) fit five basic emotion categories – Happy, Sad, Angry, Fearful, Neutral. Twenty-four words that fit well within these categories were included in Study 2. In Study 2 response options were expanded to include two additional basic emotions (Disgust, Joy), and six complex emotions (Amusement, Anxiety, Contentment, Irritated, Pride, Relief). Only half of the Study 1 words were categorised into the same emotion categories in Study 2. An increase in diversity of ratings for both positive and negative valenced words suggested overlaps in people’s conceptualisations of emotion words. Results suggest potential benefits of providing research participants complex emotion categories of varying intensity, which may better reflect people’s nuanced conceptualisations of emotion. Future research exploring varied response options may provide further insight into how people categorise and differentiate emotion words.