Cognitive testing is a qualitative method that involves asking testers to think aloud as they answer your survey questions. It helps you understand how they interpret, process, and respond to your questions, and whether they encounter any difficulties, confusion, or ambiguity. You can conduct cognitive testing in person, by phone, or online, depending on your resources and preferences. You should ask testers to explain their thoughts, feelings, and actions as they go through your survey, and probe them for more details if needed.