In the first chapter, an overview is provided of the world of psychological testing. More precisely, this chapter provides a general overview of the main topics related to the world of testing. These topics are discussed in more detail in the remaining chapters. 

What are the major categories of tests?

Broadly speaking, we can distinguish five major categories of tests: (1) mental ability tests; (2) achievement tests; (3) personality tests; (4) interests and attitudes; (5) neuropsychological tests. 

1. Mental ability tests

Mental ability comprises a range of cognitive functions, such as memory, vocabulary, spatial visualization, and creative thinking. Within mental ability tests, a further subdivision can be made: (a) individually administered; (b) group administered; (c) other abilities. A well-known mental ability test is the Wechsler Adult Intelligence Scale, also known as the WAIS. This test is an example of an individually administered test. An example of a group-administered test is the Otis-Lennon School Ability Test (OLSAT). 

2. Achievement tests

Achievements tests aim to measure a person's level of knowledge or skill in a specific domain. Achievement tests are by far the most popular type of all tests. Again, a further subdivision can be made within this major domain, this time in five subgroups: (a) batteries; (b) single subject; (c) certification, licensing; (d) government-sponsored programs; (e) individual achievement tests. An example of the first subcategory, an achievement battery, is the Stanford Achievement Test (SAT). Second, single subject tests cover only one domain, for example only mathematics, or only history. The third subcategory is used for purposes of certification and licensing. Think, for example, of certificate tests for teaching or nursing. The fourth subcategory covers tests that are sponsored by various government agencies, for example the CITO test in the Netherlands. Lastly, individual achievement tests are commonly used to aid in the diagnosis of for example learning disabilities. 

3. Personality tests

Personality tests can be further divided into: (a) objective tests; (b) projective techniques; and (c) other approaches. Objective tests are, as the name implies, tests that are objectively scored, based on items that are to be answered in a true-false, or similar, format. An example of an objective personality test is the Beck Depression Inventory (BDI). A different approach to assess personality is provided by projective techniques. Projective techniques give the respondent a rather simple, but unstructured task. It is then hoped that the respondent's response reveals information about his or her personality. The most well-known projective personality test is the Rorschach Inkblot Test. 

4. Interests and attitudes

In the fourth major category of tests, a subdivision can be made between (a) vocational interest measures, and (b) attitude scales. The former are commonly used in high school to help students explore job opportunities that match their interests. The latter aims to measure attitudes toward topics, groups, and practices. For example, there are attitude tests that aim to measure people's attitude toward the death penalty. 

5. Neuropsychological tests

Neuropsychological tests aim to provide information about the functioning of the central nervous system, in particular the brain. They are for example focused on psychomotor coordination or abstract thinking. 

What other ways are there to categorize tests?

In the section above, we categorized tests according to their content. This is the most common way to categorize tests. However, there are other ways to categorize tests, which we will briefly introduce in this paragraph. One may, for example, distinguish between a performance test and a paper-and-pencil test. One may distinguish between speed tests versus power tests, in which the former assesses how fast a respondent performs, and the latter generally does not administer a time limit. Note that this distinction is not as black and white as the former: some power tests may have an element of speeds. You can not, for example, take forever to complete the CITO test. A third distinction is between an individual test and a group test. The latter can be  (but does not have to be) administered to many individuals at the same time. Next, one can distinguish between maximum performance (How well does one performance when at his or her best?) versus typical performance (How well does one generally perform?). The latter is commonly used with personality, interest, and attitude tests. Lastly, one can distinguish between norm-referenced versus criterion-referenced test. A norm-referenced test is based on the performance of individuals in a standardization program (for example the SAT and CITO). A criterion-referenced test use a clearly defined criterion that is independent of how well other people did. 

Who are the users of psychological tests?

Many different people use psychological tests. Although there is considerable diversity within each group, we broadly classify four major contexts for the use of psychological tests: (1) clinical (for example psychologists); (2) educational (for example teachers); (3) personnel (for example the military and businesses); and (4) research. In research, tests can be used with different purposes. First, the test may serve as the operational definition of the dependent variable. For example, the WAIS may serve as a definition for what constitutes intelligence. Second, researchers may use tests to describe samples. Third, researchers may conduct research on the tests themselves, for example by assessing the psychometric properties of a test, such as reliability and validity. 

What are the basic assumptions in psychological testing?

In psychological testing, there are four basic assumptions: (1) people differ in important traits; (2) we can quantify these traits; (3) the traits are reasonably stable; (4) measures of the traits relate to actual behaviour. With quantification (the second assumption), is meant that objects (in psychology: individuals) can be arranged along a continuum. This quantification assumption is crucial to the concept of measuring. This is illustrated by the following two questions: "How did you measure the child's school performance?" and "How did you test the child's school performance?". Both questions essentially mean the same. 

What are fundamental questions in psychological testing?

There are five fundamental issues in psychological testing. First, reliability refers to the stability of test scores. For example, if I take a test today and again tomorrow, will I get (roughly) the same score? Second, a fundamental question concerns the validity of a test; what is the test actually measuring? Third, how can the scores from a test be interpreted? Interpretation of test results generally depends on the norms that are used. Fourth, how was the test developed? And fifth, what are the practical issues that need to be considered? For example, how long does the test take? It is available in all languages? And so on. 

What is the common perspective in psychological testing? 

In psychological testing, we are generally more interested in how people differ from others rather than in how different people are the same. Therefore, the common perspective in psychologica testing is the differential perspective. The differential perspective assumes that the answer may differ for different individuals.  

What is the history of psychological testing?

The history of psychological testing can be divided into seven major periods. These periods and their dominant themes are briefly summarized in Table 1.

Table 1. 

What are the major forces that influenced the development of psychological testing?

There are six major forces that influenced the development of psychological testing: (1) the scientific impulse; (2) concern for the individual; (3) practical applications; (4) statistical methodology; (5) the rise of clinical psychology; (6) computers. These six major forces are briefly discussed below. 

1. The scientific impulse

A prevailing force through the history of testing is the need to measure scientifically. This is reflected by the amount of references in writings of Galton, Thorndike, Catell, Binet, and other pioneers. Especially the clinical psychology, one of the primary fields of application for testing, has proclaimed its allegiance to the scientific approach. 

2. Concern for the individual

A second important force that influenced the development of psychological testing is concern for the individual. This is line with the differential perspective, which we discussed earlier, that is dominant within the field of psychological testing. As a result, many, though not all, of the practical applications (tests) that we will discuss throughout this book are related to concern for the individual. 

3. Practical applications

Basically every major development in psychological testing resulted from work on a practical problem instead of resulting from a theoretical consideration, which occurs to a much lesser extent. Thus, testing has been developed in response to practical needs. 

4. Statistical methodology 

The development of psychological testing is inevitably intertwined with statistical methodology. This relationship is bilateral: the field of testing 'borrows' methods from the field of statistics, and statistics developed some methods specifically in response to needs in pscyhological testing. For example, the mathematician Karl Pearson was induced by Galton to develop the correlation coefficient. 

5. The rise of clinical psychology

Clinical psychology as a field is one of the prime applicants (and developers) of psychological testing. The rise of clinical psychology is generally credited to Lightner Witmer, who in 1986 treated the "case of a chronic bad speller", what we would now refer to as a learning disability. Witmer was trained in the methodology of psychophysics and used many methods of the psychology laboratory to his case study. He also gave the first course in clinical psychology at the University of Pennsylvania. Many psychological tests are developed, and used, in clinical psychology. 

6. Computers

The sixth, recent, driving force of the development of psychological testing is computer technology. It is important to note that a computer is different from a scanner. A scanner is an electronic device that counts marks on a test answer sheet. It is also referred to as a 'reader'. This means that 'computer answer sheets' are not put into a computer. They are put into a scanner. The output from the scanner may or may not serve as input for a computer. 

The history of the relationship between computers and psychological testing comprises three phases. First, computers were used merely as an aid in statistical processing for test research. By doing so, computers allowed for much larger research programs and more sophisticated statistical methodology. Second, computers were used to prepare reports of test scores. First, they aided in preparing simple reports with, for example, raw scores (the correct number of answers) from a scanner. Later, as programming skills developed, computer-based reports became more sophisticated and new techniques for numerical and  graphical displays of results developed rapidly. An important development in this phase was the use of interpretative reports in which test performance was no longer described solely by numbers, but also with a few simple words or even continuous narrative. Third, computers aided in test administration. Here, there are two types: computed-based test administration and computer-adaptive testing. Computer-based test administration simply refers to the presentation of questions on a computer screen (instead of on paper). The questions are put into a text file and shown on a screen. Computer-adaptive testing, on the other hand, does not only present questions on a screen, but it also selects the next item based on the respondents' response of prior item(s). It is therefore more revolutionary than the computer-based test administration.

Currently, a new application is emerging: automated scoring. Automated scoring means that a computer program is used for the scoring, and that human judgement is simulated to score products, such as essays, medical diagnoses and so on. It is likely that this application with grow substantially in the field of psychological testing in the next decades. 

How do we define the term test or testing?

A last way to introduce the field of testing is by way of definition. How do we define the term test, or testing? This approach would be the standard approach to introduce the field of psychological testing in academia. However, because the authors of this book consider this perspective a boring way to start, they first discussed other ways to introduce the field. 

To define a test, it is important to summarize the characteristics that comprise it. That is, a test is (1) a procedure or device (2) something that yields information (3) about behaviour. A test does generally not focus on all behaviour, but is used to examine (4) a sample of behaviour. This is done (5) in a systematic, standardized manner. Lastly, a test concerns some form of quantification or measurement.