Psychological experimentation is a process aimed to prove that certain types of behavior are predictable under particular situations or treatment conditions. These treatment conditions are manipulated in such a way that the setting created by the experimenters will invoke participants to display behavior towards the independent variable in regularity. This, in turn, will verify the experimenters’ hypotheses regarding the behavior in question. Hence, through experimentation, causal inferences between the independent and dependent variables can be reached.
However, experimentations do not always go as planned. There are times when experimenters overlook various factors that may wrongly or unnecessarily affect the results of the experiment. These factors are known as extraneous variables, variables that are not the main focus of the study yet may produce variations in behavior. When extraneous variables become frequent and change systematically across different conditions of an experiment, results can be confounded. One of the more popularly known consequences of extraneous variables is the Placebo Effect.
Hansen and Myers (2002) explain that this is a type of social extraneous variable wherein participants react to the independent variable according to how they expect the independent variable to affect them (p. 196). Since the behavior of the participants is based on their expected effects, changes that occur may less likely be due to the independent variable. This indeed lowers the internal validity, thereby causing the results of the study to be invalid and inaccurate.
In other circumstances, the experimenters are exactly the ones creating venues for extraneous variables to affect experimentations. Like the Placebo effect’s consequence, Experimenter Effect decreases internal validity in such a way that the extraneous variable causes changes in the dependent variable, not the independent variable of the experiment. This happens when the experimenters behave in a certain manner when dealing with participants (Hansen & Myers, 2002, p. 198).
This may trigger participants to respond in a particular way between or among treatment conditions in order to fulfill the experimenters’ non-verbal cues. Fortunately, this effect may be controlled through a method called Double-blind experiment, say Hansen and Myer. This technique—when combined with consistency of instructions and processes, and objectivity of observations—can prevent the decrease in internal validity for both the experimenters and participants are not aware or are “blinded” with regard to the treatment condition they are handling or partaking, respectively (2002, p. 02).
Since both parties have no idea on the nature of the treatment conditions they are assigned to, no bias or extraneous variables shall therefore arise and results produced shall be correct. For instance, it is deemed that caffeine keeps individuals alert and awake. This may be further tested through an experiment, with a hypothesis which states that caffeine can improve night driving for tired drives.
The independent variable here is the presence or absence of caffeine in the coffee drank by the participants while the dependent variable is their performance in a car-racing video game, specifically their recorded speed after three laps. In order for both the experimenters and the participants to respond without bias, the Double-blind Method can be applied. Given that coffee does ward off drowsiness and stimulate attentiveness, what remains to be critical is the effect of caffeinated or decaffeinated coffee on performance.
Since the participants do not actually know if the coffee they are to drink has caffeine in it or not, they cannot behave based on what they think is expected from them. Likewise, the experimenters shall not be able to give indications or implications regarding the nature of the treatment condition the participants are in since they are also unaware of this. Thus, if the participants performed better subsequent to drinking caffeinated coffee or vice versa, experimenters will be sure that the presence or absence of coffee is responsible for this and not an extraneous variable.