Psychometric testing A-Z

Part 2
General Mental Ability

Implications for businesses








What is general mental ability?

General mental ability (GMA) is a term used to describe the level at which an individual learns, understands instructions, and solves problems. Tests of general mental ability include scales that measure specific constructs such as verbal, mechanical, numerical, social, and spatial ability. The overall score is considered the most important factor, explaining more variation in individual performance than specific abilities.

Why is GMA relevant to business?

General mental ability has been found to be the single best predictor of job performance across all organisations and positions; it accounts for approximately 29% of the variance in job performance. Studies have found that people with higher general mental ability acquire more job knowledge and acquire it faster. Higher levels of job knowledge lead to better performance. Objective assessments of general mental ability can significantly improve hiring decisions, staff retention and productivity.

How does GMA relate to work experience?

Many hiring decisions are strongly influenced by the extent of prior job experience. In fact while job experience does influence job performance, its relationship is weaker than the relationship with general mental ability, and the influence of experience declines over time, unlike the relationship between job performance and general mental ability.

ROI of GMA testing

GMA tests are amazingly cost effective. You can dramatically improve the quality of your hiring decisions, avoid painful mistalkes, all for a fraction of the cost of the new hire's first day at work.

Assessing likely future job performance

From a practical point of view, the most important property of a personnel assessment method is predictive validity; that is, the ability to predict job performance and job-related learning.

In comparison to alternative personnel measures, general mental ability tests have the highest predictive validity, and the lowest application cost. Work samples and simulations are slightly more valid, but are expensive to set up. Structured selection interviews often contain job knowledge components, and are therefore less suitable for inexperienced or entry-level candidates. Assessment centre approaches are both much more expensive and also have less validity. The personality factor of Conscientiousness which describes motivation, personal organisation and focus, adds additional predictive power to tests of General Mental Ability.

Ultimately, the combination of a test of general mental ability, a personality test and a structured interview is the most cost effective approach.

Tests of General Mental Ability

Tests of general mental ability measure a wide variety of constructs, as well as overall cognitive ability.

Longer tests typically measure the following dimensions:

  • General knowledge: The degree to which an individual has accumulated knowledge about diverse topics. Long-term memory.
  • Social Intelligence : In both verbal and visual forms. Ability to evaluate social behavior and likely outcomes, to apply standards for moral and ethical judgment.
  • Arithmetic: Numerical reasoning and problem solving abilities.
  • Verbal concepts: Ability to categorise, conceptualise likenesses and differences, and to make subtle comparisons.
  • Vocabulary: Extent of verbal concepts learned. Indicates communication skills, openness to information, ability to effectively use information.
  • Coding : Adaptability and speed of learning
  • Detail orientation: The ability to pick up on important details, using perceptual and analytical skills.
  • Spatial rotation: Ability to visualise objects in different dimensions and perspectives.
  • Spatial reasoning: Ability to see both the disparate parts of an object and how they fit together.
Shorter tests

Although, there are a wide variety of shorter instruments available for measuring general mental ability, the most effective, and widely used today, is the 12 minute Wonderlic Personnel Test. It incorporates a wide variety of problem types including conceptual comparisons, word and sentence meanings, deductive logic, sequential reasoning, detail matching, analysis of geometric figures, and story problems requiring mathematical solutions. Test takers must enter their answers so that, in contrast to the usual multichoice format, there is a richness of information available for evaluation. The applicant's test score can be compared against minimum recommended scores for various occupational groups.

The Wonderlic Personnel Test provides quantitative insight into how easily individuals can be trained, how well they can adjust and solve problems on the job, and how satisfied they are likely to be with the demands of the job. Higher scoring individuals will gain more from formalised training, and are more likely to effectively learn from on the job experience. In contrast, lower scoring individuals will require more detailed and explicit instruction, hands on practice, more time and repetition, and close supervision.

Tests of Critical Thinking

For managers the ability to critically evaluate business propositions and the conclusions drawn by staff is vital. The Watson Glaser is the most widely used test of critical thinking. It assesses ability on different types of critical thinking. Given a set of information and a conclusion, to assess;
  • what hidden assumptions have been made
  • what inference can be taken - the relative truth or falsity of the conclusion
  • whether the conclusion logically follows from the facts
  • the relative strength or weakness of an argument and conclusion
Scores can be compared with similar occupational groups and management levels.

Performance Group International Ltd.
Consulting Industrial and Organisational Psychologists
Telephone +64 9 478 5167
Fax + 64 9 478 5164

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