MODULE 8

• Extraneous variables are unwanted factors in a study that, if not accounted for, could negatively affect (i.e. confound) the data subsequently collected.
• Physical variables are aspects of the testing situation that need to be controlled. Ex. day of the week, experimental room, lightning, etc.
• Physical variables are aspects of the environment that might affect the participant’s behavior, e.g. noise, temperature, lighting conditions, etc.
• Physical variables are also called as situational variables, these should be controlled so they are the same for all participants.
• Standardized procedures are used to ensure that conditions are the same for all participants. This includes the use of standardized instructions
• Elimination


  A control technique whereby extraneous variables are completely removed from an experiment.
• Constancy


  A control technique by which an extraneous variable is reduced to a single value that is experienced by all participants.
• Balancing


  A control procedure that achieves group equality by distributing extraneous variables equality to all groups.
• Demand characteristics are cues within the experimental situation that demand or elicit specific participant responses. Subjects try to act as they feel the researcher wants them to act. Example: if researcher to tell him when they hear a tone, subjects may say they hear it even if they don’t. They are trying to be good subjects.
• Demand characteristics are when subjects pick up cues during an experiment and modify their behavior; thereby possibly affecting and altering the results of the study.
• In a psychological experiment, a demand characteristic is a subtle cue that makes participants aware of what the experimenter expects to find or how participants are expected to behave. These characteristics can change the outcome of an experiment because participants will often alter their behavior to conform to expectations.
• Demand characteristics


  Any aspect of an experiment that may reveal the hypothesis being tested or that may cue participants as to what behaviors are expected
• Cues that may reveal the true purpose of an experiment

  • Information conveyed in the solicitation of participants
  • Instructions given to participants
  • Tone of voice of the experimenter
  • Gestures used by the experimenter
  • Feedback given to participants (e.g., feedback about performance or personality characteristics)
  • The laboratory setting
  • The design of the study
  • Rumors spread by others who have participated in the study
• The presence of demand characteristics could even lead to a good subject effect, where participants are overly cooperative and behave in such a way that confirms the hypothesis of a study. Put another way, if an experiment suffers from demand characteristics, then its findings are considered neither valid nor meaningful. Demand characteristics can ruin an experiment.
• To control demand characteristics, researchers may use single-blind experiments where the research participants are ignorant (blind) to the expected outcome of the experiment.
• A single-blind study occurs when the participants are deliberately kept ignorant of either the group to which they have been assigned or key information about the materials they are assessing, but the experimenter is in possession of this knowledge.
• One way to control demand characteristics is to do a single-blind study. In a single-blind experiment, subjects are not told their treatment condition. For example, in a single-blind drug study, the experimental and control groups might receive capsules that look and taste identical. When subjects are not told their treatment condition, this eliminates cues that might alter their behavior.
• A placebo is anything that seems to be a "real" medical treatment -- but isn't.
• The placebo effect is when a subject receives an inert treatment and improves because of positive expectancies.
• Research on the placebo effect has focused on the relationship of mind and body. One of the most common theories is that the placebo effect is due to a person's expectations. If a person expects a pill to do something, then it's possible that the body's own chemistry can cause effects similar to what a medication might have caused.
• To control demand characteristics, cover stories are used when we create an experimental situation, we want subjects to respond as normally as possible. At the very least, we do not want their expectations to alter their responses on the dependent measure. Sometimes the best control over demand characteristics is gained by using a cover story, which is a plausible but false explanation for the procedures used in the study. It is told to disguise the actual research hypothesis so that subjects will not guess what it is.
• A cover story is a false plausible explanation of the experimental procedures to disguise the research hypothesis from the subjects. It is used because we want subjects to respond as normally as possible.
• Cover story should be used sparingly, since they are a form of deception.
• Experimenter bias is any behavior by the experimenter that can confound the experiment. Experimenters may not realize it, but they can give subjects cues that tell how the experimenters would like them to respond.
• In research, an experimenter bias, also known as research bias, occurs when a researcher unconsciously affects results, data, or a participant in an experiment due to subjective influence. It is difficult for humans to be entirely objective which is not being influenced by personal emotions, desires, or biases.
• Experimenter bias can occur at any phase of the research process from the initial background research to the final write-up of results.
• Rosenthal Effect is the situation in which an investigator’s expectations about the outcome of a given study unwittingly affect the actual study outcome.
• Rosenthal effect

  This term is often used synonymously with experimenter expectancy effect and self-fulfilling prophecy.
• The Pygmalion effect is a psychological phenomenon wherein high expectations lead to improved performance in a given area.
• The Rosenthal effect is the phenomenon in which experimenters treat subjects differently based on their expectations and their resulting actions influence subject performance.
• Rosenthal Effect is also called the Pygmalion effect and self-fulfilling prophecy. For example, teachers might give more attention and feedback to high aptitude students than to low aptitude students. The Rosenthal effect can confound an experiment, producing results consistent with the experimenter’s expectations.
• The Pygmalion effect, also known as the Rosenthal effect, is the phenomenon whereby higher expectations lead to an increase in performance, named after the Ovid tale of a sculptor who falls in love with one of his statues.
• To control experimenter bias, researchers use a double-blind study in which neither the participants nor the experimenters know who is receiving a particular treatment. This procedure is utilized to prevent bias in research results.
• Double-blind studies are particularly useful for preventing bias due to demand characteristics or the placebo effect. For example, let's imagine that researchers are investigating the effects of a new drug. In a double- blind study, the researchers who interact with the participants would not know who was receiving the actual drug and who was receiving a placebo.
• Double-blind indicates that the participants and the experimenters are unaware of who is receiving the real treatment.
• Reasons to Use a Double-Blind Study

  1. First, since the participants do not know which group they are in, their beliefs about the treatment are less likely to influence the outcome.
  2. Second, since researchers are unaware of which subjects are receiving the real treatment, they are less likely to accidentally reveal subtle clues that might influence the outcome of the research.
• Personality variables


  The personal characteristics that an experimenter or volunteer subjects bring to the experimental setting.
• According to a response set called social desirability, experimenters who are high on the social desirability scale (Crowne & Marlowe, 1964) are:

  • particularly good at likable experimenters;
  • they are more enthusiastic, friendlier, and smile more at their subjects
• Interestingly, experimenters who come across as likeable can alter the kinds of responses, as well as the number of responses, obtained from subjects. For instance, studies on interviewing have shown that a likeable interviewer will collect better data, more usable responses, and fewer “I don't knows" from respondents.
• Some of the control techniques discussed will reduce the influence of personality variables. If possible, use multiple experimenters and make sure that each experimenter runs about the same number of people in each of the conditions of the experiment (in effect, balancing them across the experiment).