Keywords: Attention Checks; Online Survey; Experiments; Screener; Question of Formulation.
Since in online surveys the control over respondents is practically null, researchers have developed screener questions to assess the subjects' attention in filling the questionnaire. To successfully pass a screener question, a respondent must follow instructions described in a text that contains a varying amount of misleading information. By means of an experiment carried out in an online survey of the Italian National Election Study, with data collected in 2015 (N = 3,000), the article shows that a large proportion of respondents (≥ 50%) in an online survey does not pay adequate attention to the text of the questions, especially if the text is long and complex. Screeners turn out to be effective tools for evaluating the quality of respondents' answers especially if the cognitive load required to pass the test is low.