Overview of diagnostic procedures

If you’ve ever wondered how psychologists find out what is going on inside a person, you may have heard of diagnostic procedures. These are scientifically grounded methods for assessing a person’s behavior, emotions, and thought processes. In this blog post, we’ll look at the different types of diagnostic procedures, how they differ, and how they are applied.

General Strategies

In assessment, two fundamental approaches can be distinguished: individual and institutional assessment. While individual assessment is tailored to the individual and addresses specific questions, institutional assessment often deals with recurring, standardized questions—for example, in personnel selection or performance evaluation.

Another important distinguishing feature lies in the strategies used. Selection strategies focus on choosing people or conditions, whereas modification strategies aim to deliberately change behavior or conditions.

In practice, mixed strategies are often used, combining both approaches to obtain a more comprehensive picture and make optimal decisions.

One can also distinguish between status diagnostics and process diagnostics. This also relates to the debate between dispositionism (focus on traits) and situationism (focus on states).

Especially when evaluating and interpreting results, it is also relevant what a test result is compared with. The main possibilities are a norming sample (norm-referenced assessment) or a criterion (theoretical cut-off value).

Strategies in diagnostics: individual vs. institutional diagnostics

A key concept in diagnostics is the distinction between individual diagnostics and institutional diagnostics.

Individual diagnostics focus on the individual case and pursue a tailored approach that addresses the specific needs and characteristics of the person being assessed. Here, the entire diagnostic process is adapted to the individual, for example when selecting a suitable educational pathway for a child.

Institutional diagnostics, by contrast, are designed to address frequently recurring questions within institutions. In school systems or workplace settings, for example, standardized performance tests are used to collect regularly recurring information relevant to the organization. These procedures are less individualized and usually follow a defined process, such as general health check-ups in the workplace or standardized aptitude tests.

Selection vs. modification strategies

Depending on the diagnostic objective, procedures can be divided into selection and modification strategies.

• Selection strategies aim to choose between several options, such as when selecting personnel for a specific position. The question here is which person is the best fit for the organization.
• Modification strategies, by contrast, focus on change and development. They are often used in therapy or coaching to promote or modify specific behaviors or ways of thinking.

In addition to selection and modification strategies, diagnostics distinguishes between status and process diagnostics. While status diagnostics captures a person’s current state and thus provides a snapshot, process diagnostics focuses on changes over time. Process diagnostics is used particularly in clinical and educational psychology to observe progress and developments and respond to them in a targeted way.

What are diagnostic procedures?

In psychology, diagnostic procedures are used to collect information about a person, whether for research purposes or in clinical practice. A distinction is made between different types of procedures, depending on exactly what is to be measured and how these measurements are carried out.

In the literature, you will find a common classification of diagnostic procedures. This includes the following distinctions:

1. Performance Tests vs. Personality Questionnaires
2. Quantitative vs. Qualitative Procedures
3. Psychometric vs. Projective Procedures

Performance Tests vs. Personality Questionnaires

One key distinction is whether a test is intended to assess a person’s performance or personality.

• Performance tests (e.g., intelligence tests) measure a person’s ability to solve specific tasks. One well-known example is the Intelligence Structure Test (IST 2000 R), which measures various cognitive abilities. Participants are given tasks that require them to solve problems or draw logical conclusions. The results are then compared with a norm group to determine how well the person performs in comparison with others.
• Personality questionnaires, on the other hand, are based on self-reports and assess stable personality traits. Well-known examples include the NEO-FFI (a questionnaire for measuring the five major personality factors, such as neuroticism, extraversion, and openness to experience). These tests ask participants to rate statements about their behavior and feelings—for example, how strongly they agree or disagree with particular statements.

Quantitative vs. Qualitative Procedures

Another distinguishing feature is the degree of structure and the way the results are evaluated.

• Quantitative methods are highly structured and produce measurable results. Examples include standardized tests that capture specific values, such as an IQ test. These values can then be analyzed statistically and compared with normative data. The aim is to make objective, generalizable statements about the person being tested.
• Qualitative methods, by contrast, are less structured and leave more room for interpretation. Open conversations, interviews, and projective methods (such as the Rorschach test) take center stage here, seeking to understand the person’s subjective experiences. In these methods, exact figures matter less than how a person interprets particular stimuli or questions.

Psychometric vs. Projective Methods

The distinction between psychometric and projective methods concerns the degree of standardization and objectivity.

• Psychometric tests are characterized by their high degree of objectivity and reliability. These tests are designed to produce reproducible results that can be readily verified statistically. One example is the Beck Depression Inventory (BDI-II), which quantifies the severity of depression. Test participants answer questions, and a diagnosis is made based on the results.
• Projective techniques, on the other hand, work with less structured tasks and assume that people reveal unconscious aspects of their personality in this way. A classic example is the Rorschach test, in which the test taker has to interpret inkblots. The idea is that these interpretations can provide insights into the person’s inner conflicts or hidden desires.

How are these methods applied in practice?

Depending on the purpose of the psychological assessment, different diagnostic methods are used. In practice, a combination of different methods is often used to obtain a comprehensive picture of the person being assessed. For example, a clinical assessment might use both ability tests and personality questionnaires to determine whether a person is suffering from a mental disorder and how severe it is.

Example: Intelligence assessment using the IST 2000 R

The IST 2000 R is a classic intelligence test that measures various cognitive abilities, such as logical reasoning and spatial visualization. Suppose you want to find out how well you can draw logical conclusions. In that case, you could complete a section of the IST 2000 R that measures precisely this ability. You would have to solve a series of tasks in which you identify which figure fits into a sequence or which pattern comes next in a series.

Example: Personality assessment using the NEO-FFI

Imagine you wanted to find out how extroverted or neurotic you are. Then you could take a test such as the NEO-FFI. You would answer questions like: “I enjoy being the center of attention” or “I often worry.” Based on your answers, the test would show you where you fall on the scale of Extraversion and other personality dimensions.