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section one

Introduction to ability testing

Ability tests, also known as aptitude tests, cognitive ability tests, or intellect assessments, are the world’s most commonly used psychometric assessments. Thousands of graduates and apprentices are tested every year as part of recruitment programmes. Managers and experienced professionals are also well represented, often completing longer and more cognitively challenging assessments as part of high-stakes selection procedures. Ability tests have become a mainstay of early-stage selection processes and all the evidence indicates that their usage is only increasing.

The common job interview is viewed as the main selection tool by many, but thinking is shifting and the evidence is clear that ability tests are king.

A 1998 paper by Schmidt and Hunter suggest that not only should ability tests be considered the primary selection tool when making hiring decisions, but all other selection tools should be viewed as mere supplements, highlighting their relative importance. Since then, new evidence has come out that could suggest ability tests are even more effective at predicting job performance than we first thought.

section two

What is an ability test?

Ability tests are standardised assessments which measure specific cognitive aptitudes, such as verbal reasoning, numerical reasoning, and inductive reasoning.

Each of these aptitudes measures an individual’s ability to work with that specific information source. For example, people who score highly on verbal reasoning are especially skilled when working with written or spoken information (qualitative data). Similarly, people who score highly on numerical reasoning tests are well suited to solving problems based on quantitative data, readily turning numerical information into something actionable. Lastly, people who score highly on inductive reasoning tests are able to identify patterns and solve non-verbal problems, which are essential to abstract thinking and complex problem solving.

What is a general ability test?

A general ability test is a test which will combine questions which assess different aptitudes in order to determine someone's general reasoning ability.

General cognitive ability is a broad, overarching measure of a person’s cognitive horsepower, determining how well they can learn, solve problems, and make effective decisions in general. GCA is not aptitude specific like aptitude tests, and those scoring highly on GCA overall will be able to work with any information source, regardless of whether it is quantitative, qualitative, or abstract.

"Ability tests become exponentially more powerful when used in combination, as a battery of ability tests will form an overall measure of general cognitive ability (GCA)."

- Ben Schwencke
section three

Benefits of ability testing in recruitment and selection

Although the reasons to add ability tests into your selection processes are plenty, there are four key reasons to do so. In this section, I will outline those four key benefits of ability testing in recruitment, and explain why ability tests are particularly useful in meeting these four aims:

Key Aim 1: Job performance

The main reason to incorporate ability testing into your selection processes is that they are the strongest predictors of real-world job performance known (Schmidt & Hunter, 1998). Moreover, as the cognitive complexity of the job increases, so too does the predictive power of ability tests. For example, in highly complex managerial work, ability tests account for more than half the variance in performance, making cognitive ability tests in hiring more important than all other determiners of performance combined. No other employee selection tool is as predictive of performance as a battery of ability tests, making them indispensable tools when it comes to maximising the quality of hire and identifying high potential candidates.

The reason behind the predictive power of ability tests is simple to understand. Research shows that ability tests scores are especially predictive of the following work-related behaviours and skills (Gottfredson, 1997):

  • Dealing with unexpected situations
  • Ability to learn and recall job-related information
  • Ability to reason and make judgments
  • Ability to identify problem situations quickly
  • Reacting swiftly when unexpected problems occur
  • Ability to apply common sense to solve problems
  • Ability to learn new procedures quickly
  • Alert and quick to understand things
  • Ability to compare information from two or more sources to reach a conclusion

Not only are these specific abilities extremely applicable to the workplace, but they tend to be especially high impact. For example, being able to solve problems quickly can be make or break, helping to avoid disaster when the worst occurs. Similarly, the ability to learn and recall job-related information is essential to performance in all areas of work, impacting performance across the board.

Not only does higher cognitive ability tend to maximise performance, but lower cognitive ability vastly reduces one’s ability to perform at work. Those scoring low on cognitive ability tests tend to struggle in all fields of work, but especially complex work, failing to meet the learning demands of the role and struggling to carry out their tasks without errors.

Overall, cognitive ability allows people to learn, solve problems, make effective decisions, react quickly, and deal with uncertainty, making it a hugely valuable asset when maximising the performance of employees. To summarise the academic consensus around ability testing and job performance, Hunter (2002) said “The purely empirical research evidence in industrial and organisational psychology showing a strong link between GCA and job performance is so massive that there is no basis for questioning the validity of GCA as a predictor of job performance”.

Key Aim 2: Training performance

When it comes to emerging talent recruitment in particular, the trainability of employees is a major selection criterion. In structured graduate, apprentice, and internship schemes, employers spend huge sums of money and invest significant resources into their graduates, largely in the form of training schemes, qualifications, and professional certifications. Although this investment into emerging talent usually generates an extremely high return, it does rely on hiring staff who can effectively absorb and apply what they have learned in their future role, otherwise it becomes an exercise in futility.

Research not only shows cognitive ability to be the strongest predictor of training performance known, but it’s an even stronger predictor of training performance than job performance (Schmidt & Hunter, 1998). This is because cognitive ability increases a person’s bandwidth for learning, allowing them to acquire and retain more information. Intuitively, this makes sense, as we all implicitly realise that cognitive ability is the primary determinant of learning, with smarter people learning the most from structured training and educational programmes. However, what many do not realise is that this effect is linear, and thus lower cognitive ability staff will desperately struggle to benefit from complex training programmes. This has three important implications:

  • The ROI from training is reduced in lower cognitive ability staff, as they will simply fail to grasp the key concepts and thus will not apply these principles in-role.
  • Training programmes do not bring lower cognitive ability staff up to speed, and instead just represents time and money wasted unnecessarily.
  • The more training that is offered to staff, the more important cognitive ability will be, meaning that cognitive ability must be strongly emphasised during the selection process.

Moreover, lifelong learning and ongoing professional development is increasingly emphasised at all levels, not just in emerging talent. This makes hiring low-cognitive ability staff even more dangerous, as you will be onboarding staff who will struggle to keep up at every stage in their careers, falling behind their peers year upon year. Not only will this exasperate any capability issues, but will inevitably reduce employee engagement, leaving those employees feeling inadequate and out-shined by their colleagues.

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Key Aim 3: Scalability, Automation, and Accessibility

A major non-psychometric advantage of modern ability tests, is that they are online and highly scalable, allowing HR teams to evaluate tens of thousands of applicants in mere hours. No other selection tool offers this level of automation, especially when used as part of a high volume recruiting sift.

Screening candidates is also especially simple, requiring HR teams to simply rank order the candidates by their score and apply an appropriate cut-off, progressing sufficiently high scoring candidates and screening out those who failed to meet the standard. Contrast this with non-scalable selection tools, such as face-to-face interviews, which take up several hours of time to plan, arrange, conduct, evaluate, and provide feedback for.

Considering that ability tests generally outperform most interviews in terms of predictive power, this makes ability tests a particularly high-return selection tool from a time and cost perspective.

Psychometric testing platforms, like Test Partnership, are also designed to work in tandem with applicant tracking software (ATS) packages, integrating the software together using an API. This means that HR teams and hiring managers can invite candidates to complete ability tests, and access the subsequent results directly from their ATS, minimising the number of platforms that they need to individually manage. This simplifies the recruitment cycle, ensuring that everything you need is under a single platform.

Ability tests can also be completed on a wide range of devices, including desktop, laptop, tablet, and mobile devices, making them far more accessible than other tools. Many ability tests, especially those designed in line with gamification principles, could be designed specifically for mobile, making them particularly accessible to those who do not have immediate access to a desktop or laptop device. Similarly, psychometric testing platforms are usually designed to be compatible with screen reader software and other accessibility packages, ensuring that almost everyone is able to participate fairly.

Key Aim 4: Objectivity and Fairness

The second non-psychometric benefit of ability tests is their objectivity, as they do not require a human marker or assessor who may introduce unconscious bias into the selection process. This removes the possibility of interpersonal bias (whether intentional or unintentional) from this stage in the recruitment process, ensuring that high performers aren’t screened out due to irrelevant demographic factors.

For example, during a traditional CV sift, hiring managers may unintentionally show preference to candidates from specific backgrounds, usually benefiting candidates from majority groups or with higher socio-economic backgrounds.

Using online ability tests however, does not allow the biases of assessors to affect selection decisions, as the only factor which will determine success or failure is performance on the test itself. As a result, ability tests are most commonly used immediately after application, ensuring that human bias cannot enter the recruitment process during the short-listing stage.

Moreover, during the initial research and development of the ability tests, psychometric test publishers will conduct adverse impact analysis and differential item functioning (DIF) analysis. This ensures that the assessments themselves are not inherently biased against candidates from specific demographic groups, i.e. based on ethnicity, age, or gender etc. Questions which are found to be disproportionately difficult for a particular group will be removed before taking the product to market, ensuring fairness and objectivity from the outset. Few other employee selection tools undergo such rigorous quality control, and as is the case with interviews, most selection tools undergo no quality control at all.

section four

Four things to look for when choosing ability tests

Now that you are aware of the benefits of ability tests, how should one go about choosing a provider? Such questions are of paramount importance, as the ability testing stage of a recruitment process is likely to screen out more candidates than any other. Large organisations may test 10-100 times more candidates than they interview. As a result, getting the ability testing stage right is of vital importance to ensure a quality shortlist, making all subsequent stages in the recruitment process considerably easier.

Aside from the obvious indicators of quality, such as validity and reliability, certain scientific advances in psychometric testing have arisen that maximise the practical utility of ability tests. Here, I will outline five key determiners of quality for ability testing which take into account more modern advances in the field of psychometric testing.

Item banking

With online assessments now the norm, the threat of cheating on these assessment is at an all-time high. To combat this, we always recommend using ability tests that utilise item banks for online unsupervised testing. Item banks are large banks of questions, ensuring that each candidate gets a unique combination of questions.

To make this work, test publishes take into account the difficulty of the questions themselves, as well as the number of correct responses. This frees the assessment from needing to use a fixed set of questions, providing a massive barrier to cheating. Should candidates attempt to cheat by leaking and distributing the questions from a specific test attempt, that would offer almost no benefit to cheating candidates, as each candidate will receive a unique set of questions.

Moreover, we recommend against using fixed-form testing in any context, not just for unsupervised testing. This is because candidates could discover a leaked version of the assessment and memorise the answers in advance of a supervised assessment setting. Even if they only memorise the answers to a few questions, that still represents an unfair advantage that is not afforded to more principled candidates.

Lastly, offering fixed-form ability tests these days implies a lack of psychometric expertise on the part of the assessment provider. Knowledge of related psychometric theory, including item response theory (IRT) which permits item banking has become common place in psychometric testing provider circles, and the inability to provide item banked tests suggest a major lack of ability in this domain.


We recommend choosing assessments which employ Computer Adaptive Testing (CAT) methodologies. CATs use their large item banks to tailor the testing experience to each specific candidate, getting harder following correct answers and easier following incorrect answers. This allows the test to home-in on the candidate’s true level of ability, using both the difficulty of the questions and the number of correct responses to calculate a candidate’s score. This has a number of advantages over giving candidates a random selection of questions:

  • 1) Greater reliability: Because candidates are never given questions which are too easy or too hard for them, the questions they are given are always maximally informative, providing a more accurate score. Moreover, because the questions are always appropriately targeted, this minimises guessing behaviour or careless mistakes, which happen when candidates are given tests which are too easy or too hard for them personally.
  • 2) Quicker testing times: Because the scores are significantly more reliable, test publishes can shorten the length of their assessments without seeing large drops in reliability. This ensures that tests can be shortened to an appropriate length, minimising the time commitment from the candidates while still ensuring highly precise scores.
  • 3) Better candidate experience: By adapting the difficulty to each individual candidate, the testing experience can be optimised. Candidates will not be given questions that are too hard or are excessively easy for them, giving every candidate a challenging, but not overwhelming testing experience.

Because modern ability tests should be item banked, the length of the assessment should be entirely customisable. This has important implications for tailoring the assessment to specific populations and managerial levels. For example, graduates and apprentices are very comfortable completing quick online assessments, and are expecting the testing experience to be relatively succinct.

Executives and senior managers however, who are more dubious about completing online assessments in the first place, will be expecting something more akin to an executive specific assessment, anticipating a far longer assessment with a more robust feel.

Therefore, test publishers must have the ability to customise the length and messaging around the assessment to fit the expectations of the candidates.

Similarly, the name of the assessment and its instructions should be customisable based on the role / level of the candidate. Traditionally, assessment suites have been fully off-the-shelf, keeping the names and related messaging consistent. However, to truly maximise uptake and the probability of senior level candidates completing the assessments, we believe that these details should reflect the role, not the assessment suite. For example, changing the name of the assessment to “[[company_name]] Executive Numerical Assessment” is likely to highlight its importance to senior candidates, increasing the proximity of compliance and completion.

Gamified and traditional versions

Gamification has begun revolutionising the field of ability testing, creating new and exciting avenues for further research. Gamified ability tests have proven themselves to be just as effective as traditional ability tests, perhaps even more so, as they allow for the creation of more cognitively complex tasks. However, traditional ability tests still have their place, and more senior candidates will almost certainly prefer a traditional ability test to something which is gamified. With this in mind, we advise working with a test provider that can offer both modalities of assessment. In doing so, you are able to utilise gamified ability tests for emerging talent recruitment, which will almost certainly improve the candidate experience. Similarly, traditional ability tests are likely the preferred option for experienced professionals, managers, and executives, stressing upon them the seriousness of the endeavour and showing the appropriate level of respect.

section five

Ability test best practices

Assuming you have done your due diligence and have chosen a provider that offers the above advantages, how should you utilise these assessments for specific roles? In this section, I will go over the various ways to use ability tests at various levels of recruitment to maximum effect.

Blue Collar Workers

Although ability tests tend to be used less frequently in blue collar roles, research suggests that they are still useful predictors of future performance in even the simplest of roles (Schmidt & Hunter, 1998). As a general rule, ability test pass marks need not be extremely high, and instead can simply ensure a reasonable minimum benchmark of scores. This ensures that all candidates meet a minimum requirement for numeracy and written skills, along with a requisite level of trainability. The assessment experience should be kept relatively quick, taking around 30 minutes to complete overall.

Administrative and clerical work

Ability tests are used frequently in these roles, as they are often quite high-volume. We recommend using ability tests early in the recruitment process, ideally after a CV sift or application form. As with blue collar workers, we recommend meeting a minimum standard, albeit a slightly more rigorous one. As a general rule, you should be screening out around 20-40% of candidates using the ability tests, and thus should choose a cut-score which allows you to achieve this. The assessments should also be fairly quick, taking between 30-45 minutes or so to complete.

Emerging Talent Recruitment

Ability tests are perhaps the most useful in emerging talent recruitment, due to the cognitive complexity of the roles, the trainability requirements, and the high volumes. We recommend using the ability tests as early as possible, ideally immediately upon applying. Organisations are advised to be as selective as they can possibly be, and feel comfortable screening out 50%-90%+ of their applicants using ability tests. The ability tests must be kept relatively short, as candidates are likely busy with their studies and on other recruitment processes, with 30-45 minutes being reasonable.

Experienced Professionals

Many employers feel less comfortable using ability tests with experienced employees, which we feel is unwarranted. Instead, we recommend using ability tests, but doing so carefully, ensuring that the messaging is appropriate and the length of the assessment is tailored to the role. With experienced professionals, the tests must be somewhat longer and more robust feeling, typically taking 45-60 mins to complete. This ensures that testing feels rigorous, and that selection decisions based upon them will seem fair.

Managers and Executives

With senior managers and executives, ability testing must be handled very carefully. Ability tests offer a huge ROI when used with senior managers, but only if they actually complete them. To maximise that outcome, we recommend tailoring the messaging to be specific to executive recruitment, highlighting the importance of this stage. Moreover, ability tests should form part of a larger battery of assessments, including personality questionnaires or situational judgement tests, taking an hour or two to complete. The goal here is to highlight to candidates that this is an executive-level assessment process, and that any assessments used to make a decision will be highly robust.

section six

The Limitations of Ability Tests

While this article has been largely complimentary to the use of ability tests in employee selection, we must also acknowledge the limitations of such assessments. Although they are incredibly powerful recruitment tools, they are designed to measure a specific set of psychological constructs, and thus do not capture every aspect of performance.

In this section, I will discuss the limitations of ability tests, focusing on what they cannot or should not be used for:

Ability tests do not predict contextual performance

Ability tests are excellent predictors of task performance, the primary technical or practical demands of the role. However, ability tests do not address contextual performance, the social and psychological aspects of the role which contribute to the organisation indirectly. For example, smart employees may be more effective at reaching their KPIs, but there is no guarantee that they will attend work drinks, put in overtime, or put themselves forward for difficult jobs. Contextual performance and organisational citizenship behaviours are more closely aligned to personality traits and behavioural dispositions than cognitive abilities, and thus recruiting for cognitive ability alone will not maximise this form of performance.

Does not address organisational culture-fit

Cognitive ability is not a predictor of organisational culture-fit, person-environment fit, or even person-team fit, and cannot be used as a proxy to measure them. Naturally, we have all met people who are highly technically proficient, but struggle to fit into their organisation or team, resulting in lower employee engagement. Cognitive ability does not predispose a person towards particular values, principles, or broad overarching goals, and thus scoring highly on a cognitive ability test on its own doesn’t guarantee culture-fit. Instead, behavioural assessments and interviews must be included to ensure organisational-culture fit, as ability tests are simply not designed to measure these traits.

Does not predict tenure length or retention

Performance and retention are two separate issues, at least after accounting for capability issues. Although very low performers on cognitive ability tests are likely to leave their role early (by choice or otherwise), at the middle and high end of performance the evidence does not suggest that cognitive ability is associated with tenure length. Naturally, the smartest and most technically proficient staff are in high demand in the employment market, and are just as likely to seek alternative employment as anyone else. That isn’t to say they are more likely to leave than lower scoring employees, merely that ability tests will not be an effective tool for improving employee retention. Instead, behavioural assessments targeted to organisational-fit or role-fit should be recommended, and will have a far greater positive impact on retention rates.

Does not address soft skills, such as EI, interpersonal skills, or resilience

A wide range of soft skills, personality traits, and behavioural dispositions are essential to performance at work, but are entirely unmeasurable using ability tests. For example, interpersonal skills and emotional intelligence (EI) are key to working with colleagues, customers, managers and stakeholders, but are not measured directly by ability tests. Similarly, certain intrapersonal traits, such as resilience, conscientiousness, industriousness, and integrity are vital for both task and contextual performance, but fall completely outside the remit of ability tests. Instead, a personality questionnaire should be utilised to measure these traits, creating a well-rounded profile of each candidate.

section seven

Conclusion and recommendations

Cognitive ability, as measured by ability tests, is the most important individual psychological variable known to man. It quite literally separates humanity from the rest of the animal kingdom, and has allowed us to thrive in ways never before seen in nature. Cognitive ability is the primary factor that distinguishes Nobel Prize Laureates and tech billionaires from chronic underachievers, and is by far the largest individual predictor of success in school, work, and in life more generally.

That being said, cognitive ability is but one piece of the puzzle, and a wide variety of behavioural characteristics exist which will either compliment high cognitive ability or compensate for lower cognitive ability.

With both the advantages and limitations in mind, in closing I will outline the four main recommendations for using ability tests in recruitment and selection:

  • Use ability testing for every role, and at every level of recruitment: Cognitive ability is ubiquitously associated with performance in the workplace, and should be used in every role you recruit for. In the past 100 years of research in organisational psychology, not a single role has been identified where performance isn’t meaningfully associated with cognitive ability, and thus the odds of your organisation being the exception is extremely small.
  • Choose ability tests that are item banked and adaptive: It simply isn’t safe to use fixed form assessments in 2023, as those assessments will have been compromised almost immediately after they were placed online. Instead, look for ability tests that use large item banks and employ computer adaptive testing (CAT), minimising the threat of cheating and ensuring that your assessment provider has a high level of psychometric expertise.
  • Choose ability tests that can be adapted to the role and level: Item banked assessments are easily shortened and lengthened, meaning ability tests can be customised at the role level. Generally speaking, high volume recruitment requires light-touch assessments, focusing on convenience and short administration times. High-stakes recruitment however, must feel robust, requiring a longer and more serious testing experience.
  • Use behavioural assessments alongside ability tests: Behavioural assessments are the ideal tool to compliment ability tests, measuring the predictors of contextual performance that are unrelated to cognitive ability. By combining both assessment modalities, you create a comprehensive profile of each candidate, allowing you to make highly informed selection decisions quickly, conveniently, and most of all fairly.

The employer evaluates the candidate’s potential, requiring varying degrees of investment from the candidate. This ranges from low-touch CV sifting, to very high touch assessment centres, and indeed everything in between. In return, the candidate is given feedback, reassured as to the employers continued interest in their application, and hopefully offered a job at the end. The candidate needs to feel the effort justifies the eventual reward, and that the process itself is designed in a fair and effective way.

"The candidate needs to feel that the process itself is designed in a fair and effective way"

- Ben Schwencke

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