In a within-groups design, exposing participants to one level of the independent variable can change how they respond to the other levels of the independent variable. This problem is generally referred to as – effects, of which there are various types. One specific type is known as a – effect. This occurs when exposure to one level of the independent variable contaminates how other levels of the independent variable are perceived. Another type is a – effect, which occurs when participants change their responses based on repetition of the independent variable rather than on the influence of the variable itself. It is also possible that repeated exposure to the independent variable may cause participants to guess the hypothesis of the experiment, also known as –.