Cpi Variables in Relation to the Polygraph Performance of Police Officer Candidates

This 1981 study examined the relationship between California Psychological Inventory (CPI) scores and polygraph test outcomes among police academy applicants. The research found that applicants scoring highest on impression management measures were most likely to pass pre-employment polygraph screening, raising questions about what polygraph screening actually assesses in applicant populations.

Field study of police academy applicants who completed both the California Psychological Inventory and standard pre-employment polygraph examinations, with correlation analysis between CPI scales and polygraph pass/fail outcomes.

Background & Context

In the early 1980s, pre-employment polygraph screening was rapidly expanding in law enforcement agencies across the United States. Police departments faced mounting pressure to identify candidates with integrity and suitability for law enforcement work, yet little empirical research existed examining the relationship between personality characteristics and polygraph test outcomes in this screening context.

Steven Thurber's 1981 study addressed a critical gap by investigating how scores on the California Psychological Inventory (CPI)—a widely-used personality assessment tool—related to polygraph performance among police officer candidates. The California Psychological Inventory, developed by Harrison Gough, measures normal personality traits relevant to interpersonal behavior and social interaction, making it particularly relevant for occupations requiring public trust.

This research emerged during a period when both psychological testing and polygraph screening were becoming standard components of law enforcement hiring processes, yet the interaction between these two assessment modalities remained poorly understood. The study's focus on impression management—the tendency to present oneself favorably—raised important questions about what polygraph screening actually measures in applicant populations.

Research Design & Methodology

The study examined police training academy applicants who completed both the California Psychological Inventory and pre-employment polygraph screening examinations. The research design allowed for correlation analysis between CPI scale scores and polygraph test outcomes (pass/fail decisions).

Key methodological elements included:

• Sample consisted of actual police academy applicants undergoing routine pre-employment screening
• California Psychological Inventory administered to assess personality characteristics and social desirability
• Standard pre-employment polygraph examinations conducted by professional examiners
• Analysis focused on impression management scales and their relationship to polygraph outcomes

The field setting provided ecological validity but also introduced the typical limitations of archival research with real applicants, including inability to establish ground truth regarding deception and potential selection bias in the sample.

Results & Key Findings

The central finding was that police academy applicants who scored highest on the CPI's impression management measure were most likely to pass the polygraph screening test. This represented a paradoxical result that challenged assumptions about what polygraph screening detects.

The positive correlation between impression management and polygraph passage suggested that:

• Applicants skilled at presenting themselves favorably on psychological tests also tended to produce "truthful" polygraph outcomes
• Social desirability and self-presentation skills may influence physiological responses during polygraph testing
• The polygraph may be assessing anxiety and self-presentation style as much as deception

This finding contradicted the assumption that impression management would be associated with deception or polygraph failure. Instead, it suggested that confident, socially skilled applicants with positive self-presentation were advantaged in both assessment modalities.

Discussion & Significance

Thurber's findings had important implications for understanding what pre-employment polygraph screening actually measures. If impression management ability predicts polygraph passage, the test may be selecting for psychological comfort and social confidence rather than honesty per se. Individuals skilled at managing their public image may also be better able to remain physiologically calm during polygraph examination.

The results align with broader critiques of the polygraph's theoretical foundation. Critics have long argued that polygraphs measure anxiety and arousal rather than deception, and that individual differences in anxiety responsiveness create systematic biases. Applicants high in impression management may possess lower baseline anxiety or better emotional regulation, leading to fewer physiological responses interpreted as deception indicators.

This study contributed to an emerging literature questioning the construct validity of pre-employment polygraph screening. It suggested that polygraph outcomes in applicant populations may reflect personality characteristics and test-taking confidence as much as truthfulness, raising concerns about differential impact on applicants with varying social and psychological characteristics.

Limitations & Considerations

The study faced inherent limitations common to field research on polygraph screening. Without ground truth or verified criteria, it was impossible to determine whether high-impression-management applicants who passed were actually more honest, equally honest but less anxious, or potentially more deceptive but better at concealing it. The absence of outcome validity data meant the practical significance of the findings remained uncertain.

Additionally, the correlational design could not establish causation. The relationship between CPI impression management scores and polygraph outcomes might reflect common third variables, examiner biases, or complex interactions between personality and physiological responding. Generalizability to other applicant populations and polygraph techniques was also unknown.

Practical Applications

For polygraph practice, this research highlighted potential problems with using screening polygraphs as standalone tools for applicant evaluation. Agencies should recognize that polygraph outcomes may be influenced by personality factors unrelated to honesty, and that psychologically sophisticated or socially confident applicants may have systematic advantages. Integrating polygraph results with comprehensive psychological assessment and background investigation remains essential rather than relying on polygraph decisions in isolation.

For personnel selection, the findings suggest caution in interpreting polygraph screening results. High-impression-management individuals may simultaneously score well on psychological tests designed to detect favorable self-presentation and pass polygraph screening—potentially creating a paradox where measures intended to detect dissimulation instead correlate positively with each other. This underscores the importance of multi-method assessment and careful consideration of what each selection tool actually measures.