The science of PLI


Background theory
The underlying principle of measurement in the Professional Learning Indicator® is rooted in Charles Edward Spearman’s analysis of human intellect, which identified the factor g for general cognitive ability. Traditionally g cannot be measured directly, but the PLI is a very strong indicator hereof. Research has shown that the higher the level of g, the higher the level of performance on the job. This correlation is present in all jobs and along all dimensions of performance. The effects of g are linear, i.e. successive increments in g lead to successive increments in job performance. The more complex the job, the higher the correlation between job performance and g.

Literature and books
Schmidt and Hunter (1998) summed up the research at the time and noted the following about measuring general cognitive abilities in personnel selection:

“….(general cognitive ability) has the highest validity and lowest application cost…..the research evidence for the validity of (general cognitive ability) measures for predicting job performance is stronger than for any other method…..(General cognitive ability) has been shown to be the best available predictor of job-related learning. It is the best predictor of acquisition of job knowledge on the job and of performance in job training programs…..the theoretical foundation for (general cognitive ability) is stronger than for any other personnel measure.”

Today it is widely accepted among leading scientists within the field of cognitive abilities, that there is a clear correlation between people’s cognitive abilities and their ability to learn in general, and perform on the job. Furthermore, it is widely acknowledged that there are many specialized dimensions of human cognitive abilities but one factor, called general intelligence (the g-factor), predicts better than any sub-dimension of cognitive abilities, the learning capabilities and job performance of an individual:

Hunter, J., & Hunter, R. (1984).Validity and Utility of Alternative Predictors of Job Performance. Psychological Bulletin, 96, 72-98.

Frank L. Schmidt and John E. Hunter , Select on Intelligence. Handbook of Principles of Organizational Behaviour, Blackwell Publishing, 2004.

Carroll, J.B. (1993). Human Cognitive Abilities.Cambridge University Press.

Jensen, A.R. (1998). The g Factor: The Science of Mental Ability. Westport, CT: Praeger.

Sternberg, R., Grigorenko, E. The General Factor of Intelligence, 2002, Lawrence Erlbaum Associates, Publishers, New Jersey.

Sternberg, R. Handbook of Intelligence, Cambridge University Press, 2000.

 For a full list of Cognitive Science Reading, click here

Validity and Ethics
Clients around the world rely on the Professional Learning Indicator® for a number of uses such as employee selection and talent management. Our clients use PLI® because of its science-based, easily applicable and very reliable results. PLI® assigns considerable resources to research, ensuring that the Professional Learning Indicator is in compliance with the requirements for assessment tools in terms of validity, reliability, privacy and data protection.

The careful selection and combination of questions ensure that the Professional Learning Indicator® is a highly g-loaded assessment and thus may be used as a test of cognitive abilities in connection with recruitment or internal selection of people. Various meta-analyses of g and job performance point to g as the best single predictor of job performance across jobs, emphasising the applicability of PLI® in creating a competitive organisation.

PLI® was developed in compliance with the guidelines laid out by with Equal Employment Opportunity Commission (EEOC) as well as the standards set out by the American Psychological Association (APA) and the Society of Industrial & Organizational Psychology (SIOP). During the development of the assessment the entire database of questions was reviewed by multiple individuals with different cultural backgrounds (ex. African, American, Asian, European etc.) and any items that could not be changed to sufficiently address the cultural reviewer’s concerns were deleted.

PLI® exists in over 50 languages and has in each case been subject to a rigorous translation process, ensuring cultural appropriateness and functionality of the final text. The translation company used is ISO 9001:2008 certified. The translated and reviewed texts were reviewed by PLI’s in-country reviewers familiar with the subject matter to assure preferred terminology and style. Analyses have been conducted that establish that the PLI scores are distributed normally. The established norm represents a global average of multiple job functions and educational levels. PLI has also conducted norm studies on more homogenous groups of people to further elaborate the applicability of PLI®.

Reliability analyses have been performed on individual languages and the high correlations stress the cultural neutrality and attest to the fact that PLI® is a reliable assessment tool and emphasises usability of PLI®.

PLI® has been compared to several well-documented tools, one of which measures the general cognitive ability. Through structured use this tool has demonstrated predictability for leadership performance over 40 years. Analyses reveal a high correlation, confirming that PLI® measures the general cognitive ability and is therefore a valid assessment tool with great applicability. PLI® assists clients in developing internal policies and guidelines ensuring that candidates are treated fairly and consistently.

Click here to see PLI® Privacy Policy. For additional information on the validity and reliability of PLI or any other additional information, please contact