Self-report measures of attitudes and personality characteristics often use items with Likert-type response scales where respondents select an answer from a range of ordered options (e.g., agree–disagree). Such response scales can differ in several formal attributes – number of options, verbal anchors, their extremity, or orientation (so-called reversed items). These may affect the reliability and validity of responses and total scores and directly affect measurement quality. With the Czech Science Foundation support (GA23-06924S), our team is researching these effects. We aim to develop a (formal) theory of response-scale format effects and provide a general psychometric model to enhance modeling them. This talk is based on our research and previous empirical evidence. It has four main goals: First, describe the effects and provide information about the known impacts of different response-scale formats on the psychometric properties of questionnaires. Second, provide existing explanations of these effects. Third, present psychometric models based on (exploratory) item-factor analysis for researching these topics. Fourth, introduce our Height Inventory and describe its advantages for researching response processes. Specific attention will be paid to the reversed items where we see the most significant research potential.