Questionnaires are used widely across psychology and permit valuable insights into a person's thoughts and beliefs, which are difficult to derive from objective measures alone.Given their importance and widespread use, it is vital that questionnaires map onto the cognitive functions they purport to reflect. However, where performance on naturalistic tasks such as imagination, autobiographical memory, future thinking and navigation, is concerned, there is a dearth of knowledge about the relationship between objective and subjective measures. Questionnaires are also typically designed to probe a specific aspect of cognition, when researchers sometimes want to obtain a broad profile of a participant. To the best of our knowledge, no questionnaire exists that asks simple single questions about a range of cognitive functions. To address these gaps in the literature, we recruited a large sample of participants (n = 217), all of whom completed a battery of widely used questionnaires and performed ecological tasks involving imagination, autobiographical memory, future thinking and navigation. We also devised a questionnaire that comprised simple single questions about the cognitive functions of interest. There were four main findings. First, imagination and navigation questionnaires reflected the objective measures of their cognitive functions.Second, memory questionnaires were associated with autobiographical memory vividness and not the number of internal (episodic) details. Hence, memory vividness may be a better measure when examining individual differences in autobiographical memory recall. Third, imagery questionnaires were better predictors of autobiographical memory vividness and future thinking than the questionnaires purporting to reflect these functions. Finally, a broad profile of information was obtained efficiently using a small number of simple single questions, and these modelled task performance as well as the established questionnaires.Overall, therefore, questionnaires can act as proxies for behaviour. However, consideration should be given to what a questionnaire is actually measuring when interpreting results.