stocking made into a cap. Each prisoner was also issued a toothbrush, soap, soapdish, towel, and bed linen. No personal belongings were allowed in the cells. The outfitting of both prisoners and guards in this manner served to enhance group identity and reduce individual uniqueness within the two groups.
Induction Process
With the cooperation of the Palo Alto City Police Department, all of the subjects assigned to the prisoner treatment were unexpectedly “arrested” at their residences. A police officer charged them with either suspicion of burglary or armed robbery, advised them of their legal rights, handcuffed them, thoroughly searched them (often as curious neighbors looked on), and carried them off to the police station in the rear of the police car. At the station they went through the standard booking routines of being fingerprinted, having an identification file prepared, and then being placed in a detention cell. Subsequently, each prisoner was blindfolded and driven by one of the experimenters and a subject-guard to our mock prison. Throughout the entire arrest procedure, the police officers involved maintained a formal, serious attitude, avoiding answering any questions of clarification as to the relation of this “arrest” to the mock prison study.
Upon arrival at our experimental prison, each prisoner was stripped, sprayed with a delousing preparation (deodorant spray), and made to stand alone, naked, in the cell yard before being outfitted. After being given their uniforms and having an I.D. picture (“mug shot”) taken, each prisoner was put in his cell.
Administrative Routine
When all the cells were occupied, the warden greeted the prisoners and read them the rules of the institution (developed the previous day by the guards and the warden). They were to be memorized and to be followed. Prisoners were to be referred to only by the number of their uniforms, in a further effort to depersonalize them.
The prisoners were served three bland meals per day, were allowed three supervised toilet visits, and were given two hours daily for the privilege of reading or letter writing. Work assignments were issued for which the prisoners were to receive an hourly wage to constitute their $15 daily payment. Two visiting periods per week were scheduled, as were movie rights and exercise periods. Three times a day all prisoners were lined up for a “count” (one on each guard work-shift). The initial purpose of the count was to ascertain that all prisoners were present and to test them on their knowledge of the rules and of their I.D. numbers. The first perfunctory counts lasted only about 10 minutes, but on each successive day (or night) they were spontaneously increased in duration by the guards until some lasted several hours. Many of the preestablished features of administrative routine were modified or abandoned by the guards, and some privileges were forgotten by the staff over the course of study.
Data Collection: Dependent Measures
The exploratory nature of this investigation and the absence of specific hypotheses led us to adopt the strategy of surveying as many behavioral and psychological manifestations of the prison experience on the guards and the prisoners as was possible. The dependent measures were of two general types: (1) transactions between and within each group of subjects, recorded on video- and audiotape as well as directly observed, and (2) individual reactions on questionnaires, mood inventories, personality tests, daily guard shift reports, and postexperimental interviews.
Data collection was organized around the following sources:
1 Videotaping Using the concealed video equipment, about 12 hours of recordings were made of daily, regularly occurring events such as the counts and meals, as well as unusual interactions such as a prisoner rebellion; visits from a priest, a lawyer, and parents; parole board meetings; and others.
2 Audio recording Concealed microphones recorded over 30 hours of verbal interactions between guards and prisoners in the prison yard, as well as some within the cells and in the testing-interview room.
3 Rating scales Mood adjective checklists and sociometric measures were administered on several occasions to assess emotional changes in affective state and interpersonal dynamics among the guard and prisoner groups.
4 Individual difference scales Prior to the start of the simulation, all subjects had completed a series of paper-and-pencil personality tests selected to provide dispositional indicators of interpersonal behavior styles—the F scale of Authoritarian Personality (Adorno, Frenkel-Brunswik, Levinson, and Sanford 1950) and the Machiavellianism Scale (Christie and Geis 1970)—and to isolate areas of possible personality pathology through the newly developed Comrey Personality Scale (Comrey 1970).
5 Personal observations The guards made daily reports of their observations after each shift, the experimenters kept informal diaries, and all subjects completed postexperimental questionnaires of their reactions to the experience about a month after the study was over.
Data Analysis: Video Recordings
Special analyses were required only of the video and audio material. The other data sources were analyzed following established scoring procedures.
Since the present discussion is based primarily on the videotaped material, details of this analysis are outlined here.
There were 25 relatively discrete incidents identifiable on the tapes of prisoner–guard interactions. Each incident or scene was scored for the presence of nine behavioral (and verbal) categories by two judges who had not been involved with the simulation study. These categories were defined as follows:
Question All questions asked, requests for information or assistance (excluding rhetorical questions).
Command An order to commence or abstain from a specific behavior, directed to either individuals or groups. Also generalized orders; e.g., “Settle down.”
Information A specific piece of information proffered by anyone, whether requested or not, dealing with any contingency of the simulation.
Individuating reference Positive: use of a person’s real name, nickname, or allusion to special positive physical characteristics. Negative: use of prison number, title, generalized “you,” or reference to derogatory characteristic.
Threat Verbal statement of contingent negative consequences of a wide variety; e.g., no meal, long count, pushups, lock-up in hole, no visitors.
Deprecation/insult Use of obscenity, slander, malicious statement directed toward individuals or groups, e.g., “You lead a life of mendacity,” “You guys are really stupid.”
Resistance Any physical resistance, usually prisoners to guards, such as holding onto beds, blocking doors, shoving guard or prisoner, taking off stocking caps, refusing to carry out orders.
Help Person physically assisting another (excludes verbal statements of support); e.g., guard helping another to open door, prisoner helping another prisoner in cleanup duties.
Use of instruments Use of any physical instrument to either intimidate, threaten, or achieve specific end; e.g., fire extinguisher, batons, whistles.
Results
The results of the present experiment support many commonly held conceptions of prison life and validate anecdotal evidence supplied by articulate exconvicts. The environment of arbitrary custody had great impact upon the affective states of both guards and prisoners as well as upon the interpersonal processes between and within those role-groups.
In general, guards and prisoners showed a marked decrease in positive affect or emotion, and their overall outlook became increasingly negative. As the experiment progressed, prisoners expressed intentions to do harm to others more frequently. For both prisoners and guards, self-evaluations were more deprecating as the experience of the prison environment became internalized.
Overt behavior was generally consistent with the subjective self-reports and affective expressions of the subjects. While guards and prisoners were essentially