The Invalidity of the Stanford Prison Experiment

There are quite a few landmark research cases, such as the ones conducted by noted psychologists Stanley Milgram, Bibb Latane, John Darley, and Ivan Pavlov that form the basis of human psychological understanding to date (Bower, 2004). Another noteworthy psychologist is Philip G. Zimbardo, who conducted the Stanford Prison Experiment. Since the research report was released, Zimbardo's experiment has been met with both criticism and acclaim, but has never lost its standing within the scientific community. Regrettably, this case may be more notable for the specific and identifiable flaws. Zimbardo's research methodology, observations, and bias raise an important question concerning whether this renowned psychological experiment in really as valid as previous scientists believe.

The Stanford Prison Experiment commenced in 1971 under the instruction of Phillip G. Zimbardo, a psychologist interested in "understanding the development of norms and the effects of roles, labels, and social expectations in a simulated prison environment" (Zimbardo, 2008). The participants for the project were recruited using advertisements in two Palo Alto newspapers. Each offered compensation of fifteen dollars per day and informed potential participants of what the experiment involved. Prisoners and guards were assigned their positions randomly. All prisoners remained in the prison environment twenty-four hours a day, while guards worked in shifts and then went home. Guards did not receive any special instruction on how to treat inmates, only brief guidance on maintaining order. The lack of training guards received resulted in statements such as this from Guard M, "I made them call each other names and clean the toilets out with their bare hands" (Zimbardo, 1973, p. 393). According to Zimbardo (1973) typical methods to maintain order included: "guards insulted prisoners, threatened them, were physically aggressive, used instruments, (such as) night sticks, fire extinguishers, etc... and referred to them in impersonal, anonymous, deprecating ways" (p. 395). The experiment was forced to end after only six days because Zimbardo and his fellow scientists believed the guards became too abusive and prisoners reported feelings of depression and helplessness, among other things.

Despite the organization of the Stanford Prison Experiment, Zimbardo's partial disregard for the use of the widely accepted research process, known as the scientific method, undermines the authority of his 1971 Stanford Prison Experiment. The scientific method is an important research tool used by most scientists and psychologists in order to effectively formulate and test new ideas during study-work and experimentation. The scientific method is comprised of six main steps, which include to: observe, question, hypothesize, predict, experiment, and conclude. The fifth step of this method, experimentation, (includes) sub-elements necessary to effectively and accurately measure the results of the work done using the scientific method. One of the sub-elements in this stage require experiments or studies to be performed as a "controlled experiment," that is "the scientist must contrast an 'experimental group' with a 'control group' (Carter, 2004). Carter (2004) explains, "The two groups are treated exactly alike except for one variable being tested." The usefulness of a control group is best illustrated by a drug study in which one half of the study participants are given the experimental drug and the other half is given a placebo. The effects of the new drug can then be compared to those who took the placebo to measure its usefulness.

In Zimbardo's prison experiment, no control group was used. All the participants recruited as prisoners were subject to the same maltreatment by the guards, and held inside the same unsanitary confines. Additionally, there was no control group of guards. The lack of a control group makes it virtually impossible to pin point the exact variable that caused the type of behavior that was observed in the prison. Zimbardo holds that the mental breakdown of prisoners was based solely on the conditions of the prison, and maltreatment by the guards. Both of these factors, he presumes, caused the inmates to develop an utter disregard for their fellow man, such as apathy and lack of action during inmate abuse by guards. Furthermore, Zimbardo notes that the inmates actions were due to a will to be obedient, to conform, and to be accepted to avoid potential abuse. Abuse of power by the guards may also be attributed to prison conditions (i.e. initial uprisings by inmates), and the desire for increasing amounts of power throughout the duration of the study; the latter a factor which was heavily influenced by the increasing submission and conformity by inmates in the days following the first riot.

However, there are other possibilities for the participant's behavior. Because each participant was paid for his time during the experiment, one must consider the possibility that some, if not all, of the behavior was monetarily motivated. A study by a psychologist at the University of Minnesota found that money "promotes selfish behavior" and that "merely thinking of money makes people less likely to give help to others" (Curtin 2007). Unfortunately the true motivation or variable that caused the guards and inmates to treat each other so carelessly may never be known since Zimbardo failed to employ the use of proper control and experiment groups.

Another major problem with the prison experiment is the lack of participants, or sample size. According to Herek (2008), "Researchers usually cannot make direct observations of every individual in the population they are studying. Instead, they collect data from a subset of individuals - a sample - and use those observations to make inferences about the entire population." Thus the sample size should "correspond to the larger population on the characteristic(s) of interest" (Herek, 2008). In Zimbardo's experiment, he relates the behavior of all involved back to the global human population, both women and men, though he uses only a total of twenty-one participants for the experiment, ten students to represent prisoners and eleven for guards. Additionally, Herek (2008) points out "...smaller samples (e.g. those with fewer than 1,000 respondents) have greater sampling error than larger samples." This highlights the inaccuracy of an experiment involving a mere twenty-one people as representatives of the approximately 6.5 billion people on earth. The small sample size also leaves little room for considerations such as participant's personal biases. Furthermore, the prison experiment lacked significant cultural and ethnic diversity since Zimbardo included only one Asian male and the remaining twenty were Caucasian (Zimbardo, 1973, p. 391). Thus, his stated purpose "...to understand the development of norms and the effects of roles, etc." (Zimbardo, 2008), can only be roughly interpreted as reflective of the "norms" and "roles" of the Caucasian male population.

In addition to omitting a control group and using a small sample for representation, the Stanford Prison Experiment failed to subject its participants to the conditions that real prison inmates have to deal with in their daily lives. Among the various conditions left out of the experiment were: homosexuality, racism and discrimination, physical brutality, and indefinite confinement. Krueger and Funder believe that, "Because the work uses artificial settings, it doesn't explain how social behaviors and judgments work in natural situations" (as cited in Bower, 2004). Similarly, since all participants were aware that their "imprisonment" was not a legitimate ordeal, and that two weeks was the maximum amount of time each person was to remain "incarcerated," it is possible that the participant's behavior can be attributed to having this knowledge. Zimbardo could have ironed out some of these flaws by including homosexuals, discriminatory individuals, and minorities in the experiment, an inclusion that would have allowed the prison setting to be more convincing to participants and more reflective of the global population. He could have also provided participants with a number of possible timelines for incarceration instead of a definite two-week period in order to eliminate behavioral bias based on a finite incarceration period.

There is no question that Zimbardo's experiment quickly began to be taken too serious by all involved, including Zimbardo himself, who personally apologized in his book The Lucifer Effect (2007) stating, "I was guilty of the sin of omission- the evil of inaction- of not providing adequate oversight and surveillance when it was required... the findings came at the expense of human suffering. I am sorry for that and to this day apologize for contributing to this inhumanity" (as cited in Zimbardo, 2008). Even without the various other problems in the experiment, bias by experiment directors alone leads to experiment inaccuracy and invalidity. Furthermore, it is impossible to even account for inmate and guard behavior in the Stanford Prison Experiment due to lack of attention to key principles of the scientific method, including lack of contrast between individuals in the form of control and experimental groups. Zimbardo's exclusion of these crucial elements makes any conclusions on the "development of norms and the effects of roles" uncertain and grossly inaccurate (Zimbardo, 2008). Furthermore, the lack of inmate and guard diversity in the experiment makes it impossible to relate the purposed results with the diverse prison population, let alone the varied 6.5 billion people on the planet. If Zimbardo wanted to conduct a realistic experiment of prison interactions, norms, and roles, he should have paid more attention to the norms of the scientific method, human diversity, and sheer number of people that makes up the real world. Only by reflecting these important points could this landmark experiment have offered the world of psychology the valuable information it claimed to.

References

Bower, B. (2004). To Err Is Human. Science News, 166(7), 106-108. Retrieved February 20, 2008, from Academic Search Premier database (14162177).

Carter, J. S. (2004). The Scientific Method. Retrieved February 20, 2008, from http://biology.clc.edu/courses/bio104/sci_meth.htm

Curtin, C. (2007). Think Of Money, Be Less Helpful. Scientific American, 296(2), 25. Retrieved February 19, 2008, from Academic Search Premier (23639006).

Herek, G. M. (2008). A Brief Introduction To Sampling. Retrieved February 20, 2008, from http://psychology.ucdavis.edu/rainbow/html/fact_sample.html

Zimbardo, P. G. (1973). The Stanford Prison Experiment. In Behrens, L., & Rosen, L. J. (10^th Ed.), Writing And Reading Across The Curriculum (pp. 389-400). New York: Pearson Longman

Zimbardo, P. G. (2008). Stanford Prison Experiment: FAQs. Retrieved February 21, 2008, from http://www.prisonexp.org/faq.htm