Informed Consent in Online Studies. How Much Do Participants Really Understand, and Can That Be Changed?

Background: Participants must provide informed consent (IC) to participate in a study. To this end, they must first read through and understand the information letter and the informed consent sheet. Objectives: This online study examined whether the documents used to obtain IC are being properly read and understood, and whether the design of the format influences participants' understanding of the IC.Methods: 214 participants were randomly assigned to one of three conditions (two different information letters and consent forms and a control condition). We assessed their reading of these documents based on self-report and reading time; comprehension of the IC was assessed using multiple-choice questions. Results: Most participants did not read the IC documents completely and did not sufficiently understand the relevant contents. Regarding the IC documents, both versions lead to a higher reading rate than the control document.Conclusion: The results provide information for optimizing the design of IC forms.