Many different types of perception experiments exist, including experiments on the perception of time, visual perception, perception of personality traits, and extra-sensory perception. Scientists use various methods to investigate these different types of perception. Generally they will involve changing one small variable and measuring how much that affects people’s perception of that event or person. This enables researchers to understand how human perception works in many different contexts.
Perception experiments relating to the perception of time usually aim to see how distorted a person’s internal perception of time can be. These experiments are generally simple to conduct because they only require a stopwatch and some activities to use as variables. The researchers will ordinary set the stopwatch to measure a certain amount of time, and then get the participants to try to determine how much time has elapsed. Different activities can be performed in this time to provide a variable, and this can be used to determine how people perceive time. Most people understand that boring activities always feel as if they last for longer than enjoyable ones.
Visual perception experiments are more focused on the relationship between the eyes and the brain. These can involve anything from visual tricks, which make the participant believe he or she has observed a certain thing when they have not, to the effect expectation can have on visual perception. For example, a participant may be presented with two lines with arrow-heads on them, one with the tips of the arrows pointing inwards and the other with them pointing outwards. People often believe that one line is longer than the other, despite the fact that they are identical. Participants can also be convinced that they have seen something because they expected to see it.
The way in which people judge each other is the basis for another group of perception experiments. Researchers often look at things such as posture and weight and determine how these affect the observer's perception of a person. Computer programs are often used in this type of research so that an identical face can be used, with one variable changed. This field of psychology looks into what exactly people use to make judgments on each other.
Some perception experiments aim to investigate whether people can perceive things which the ordinary five senses are blind to. Generally, these experiments will be done on people who claim to have special abilities, such as psychics, but they can also be conducted on ordinary people. In one type of experiment, a special deck of cards featuring one of five symbols is used. The participant is asked to identify the symbol on the other side of the card to determine whether he or she has extra-sensory abilities.