Experimental method psychology uses controlled experiments to investigate the cause-and-effect relationship between variables affecting behavior and mental processes. Here are some examples:
Sleep Deprivation and Cognitive Performance
One classic example is investigating the impact of sleep deprivation on cognitive functions.
- Hypothesis: Sleep deprivation impairs cognitive performance.
- Method:
- Participants: A group of participants is randomly assigned to either a sleep-deprived group (e.g., allowed only 4 hours of sleep) or a control group (allowed 8 hours of sleep).
- Independent Variable: Amount of sleep (4 hours vs. 8 hours).
- Dependent Variable: Performance on cognitive tests (e.g., memory recall, attention span, reaction time).
- Procedure: Both groups complete a series of cognitive tests. Researchers control for other variables like diet, exercise, and time of day.
- Results: If the sleep-deprived group performs significantly worse on the cognitive tests than the control group, it supports the hypothesis.
The Stroop Effect
The Stroop effect demonstrates interference in reaction time of a task.
- Hypothesis: There will be a delay in reaction time to name the color of a word if the color of the text doesn't match the word itself (e.g., the word "blue" printed in red).
- Method:
- Participants: Participants are presented with a series of color words printed in different colors.
- Independent Variable: Congruency of the word and ink color (congruent: "red" printed in red; incongruent: "red" printed in blue).
- Dependent Variable: Reaction time to name the ink color.
- Procedure: Participants are instructed to name the ink color as quickly as possible.
- Results: Participants typically take longer to name the ink color when the word and ink color are incongruent, demonstrating the Stroop effect.
Bystander Effect
The bystander effect explores the social psychological phenomenon where individuals are less likely to offer help to a victim when other people are present.
- Hypothesis: The presence of more bystanders decreases the likelihood that any one individual will intervene in an emergency.
- Method:
- Participants: Participants are placed in a room, either alone, with one other person, or with several other people (confederates who are instructed not to react).
- Independent Variable: Number of bystanders present (alone, one other person, multiple bystanders).
- Dependent Variable: Time it takes for the participant to report a simulated emergency (e.g., hearing someone cry out for help in another room).
- Procedure: Researchers measure the time it takes for the participant to seek help.
- Results: Participants are typically slower to respond, or less likely to respond at all, when other bystanders are present.
Learned Helplessness
Martin Seligman's experiments demonstrated learned helplessness.
- Hypothesis: Animals exposed to inescapable aversive stimuli will subsequently fail to learn to escape from escapable aversive stimuli.
- Method:
- Participants: Dogs were used.
- Independent Variable: Whether or not the dogs were previously exposed to inescapable shocks.
- Dependent Variable: The dogs' behavior in a shuttle box where they could escape shocks.
- Procedure: One group of dogs was exposed to inescapable shocks. Another group was not. Both groups were then placed in a shuttle box where they could jump over a barrier to escape shocks.
- Results: The dogs that had previously experienced inescapable shocks did not attempt to escape the shocks in the shuttle box. They had learned that their actions were futile.
These examples illustrate how experimental psychology uses controlled experiments to isolate variables and determine cause-and-effect relationships related to human and animal behavior.
