Individual differences science for treatment planning: Personality traits - Harkness & Lilienfeld - 1997 - Article

What is the fundamental rule of treatment planning?

In contemporary times, having a plan is very important before treatment. For example, there are ethical obligations (informed consent), legal obligations, and financial obligations.

The 'fundamental role of treatment planning' states that a plan must be based on scientific research of the highest possible quality. Ethical and legal obligations are important, but science must determine the ultimate treatment. This fundamental rule of treatment planning places great responsibility on the therapist, who must ensure that he or she is well aware of the most recent scientific findings.

Carnap argues that if X, Y, and Z are relevant facts, all three should be included in treatment planning and none of these facts should be ignored. This article elaborates on this topic: often, fact Z is ignored. Fact Z is about the individual personality differences in clients and is very important to take into account when providing treatments.

What is the history of treatment planning?

In 1950 and 1960, the dynamics of therapeutic sessions decided how to proceed. Thus, treatment planning was not done and was even perceived as a violation of the authenticity of therapy or of the free association associated with psychodynamic therapy at the time. Criticism of this is that therapy in this era often involved clinical hermeneutical errors (interpretation errors).

Since 1980, there has been a Neo-Kraepelin approach, which stated that three things are important in therapy:

• Establishing facts to determine whether or not a person meets diagnostic criteria;
• Prepare differential and multiaxial diagnoses using the categories and language commonly used in the current DSM;
• Based on the different diagnoses, prepare different treatments.

This was widely used and made therapists feel that they were working scientifically. However, the authors of the article do not consider this as scientific. They believe that making diagnoses without taking into account differences in personality is incomplete. Many symptoms associated with certain diagnoses can arise because of the personality of individuals. For example, the symptoms considered when making a diagnosis can be:

• Extreme expressions of personality traits;
• Problematic expressions of personality traits are;
• Extreme adjustments to normal personality traits.

Thus, these forms of therapy did not meet the fundamental rule.

Loevinger drew up scientific elements to view the human personality. He stated that:

• Traits are real. Traits are defined as a reasonably stable disposition leading to a typical response in certain situations;
• Traits are not constructs. Traits are discovered by looking at behavior and measured by answers on self-questionnaires;
• Traits exist in individuals, but consist of concepts for the population. People can differ in their level on a trait, this is called a trait-dimension.

What are important findings about personality?

There are three main dimensions of traits that can be important when planning treatments. There is a difference between extraversion and introversion (Eysenck), then there are the dimensions of Positive Affect and Neuroticism. Finally, there is the finding of the term constraint, which seems to be related to psychoticism and sensation-seeking.   

There are also three ways in which individuals can differ:

• Individuals can be predisposed to enjoy life or not;
• Individuals may tend to feel bad or good;
• Individuals can vary in the extent to which they look for risks.

These differences have a genetic basis.

Personality traits are fairly stable throughout life. Stability seems to be mainly genetically determined and changes often arise as a result of the influence of the environment. The gene-environment interaction model states that people with certain genes also choose certain environments, namely environments that suit their needs. Also, there is a difference between passivity and reactivity. Passivity is about the parents: when impulsive, for example, they often provide messy environments to their children. Reactivity is about a child who is very social and therefore often gets positive reactions from the environment.

One of the most important findings is that the influence of the environment has a small effect on someone's personality.  This effect is visible in childhood but disappears as someone gets older.

The science that focuses on individual differences states that adaptation is not only about adapting to an environment, but also adapting based on his or her environment.

What are the benefits of applying knowledge about individual differences?

In addition to reducing the hermeneutical error, there are four other advantages for taking into account individual differences during treatments:

• There is more information about which problems to address;
• More realistic expectations can be set;
• Treatments can be adapted to personality;
• The patient has more opportunities to know and develop himself.

McCrae and Costa also distinguish between basic tendencies and characteristic adaptations. Basic tendencies refer to someone's traits, for example someone is high in negative affect. Characteristic adaptations are about people smoking or drinking, for example. It is important that the person who plans the treatment takes into account that new, healthy characteristic adjustments are created that fit the basic tendencies of an individual.

What is the conclusion?

All in all, the authors state that therapists must consider the science of personal differences in order to comply with the fundamental rule of treatment planning. So, treatment planning should only be based on the best scientific literature available.