Through psychological research, hundreds of assessment tests have been developed to objectively and precisely measure various aspects of psychological functioning - e.g. intellectual potential, achievement, aptitude, interests, neurological functioning, personality characteristics and emotional illness and health.

Only licensed psychologists with doctoral degrees can administer, score and interpret psychological tests in an independent (non-hospital or university) setting.. Other mental health professionals (psychiatrists, social workers, counselors) are not generally trained in the administration, scoring and interpretation of psychological tests.

Some of the more common psychological tests measure:

Intellectual potential (IQ)
The concept of IQ was originally developed as a comparison between a person's chronological age and intellectual age. It was called an "intelligence quotient" because the intellectual age was divided by the chronological age to arrive at a quotient. The IQ concept was abandoned in favor of a derived standard score, which is a better way to compare the scores of different individuals, but the IQ label has been maintained. An IQ score is useless as a comparative measure of intelligence without knowing which test was used to obtain the score. The most well-known tests of intelligence are the Wechsler Scales and the Stanford-Binet. However, there are many other ability tests that measure intellectual functioning.

Memory Functioning
Most intelligence tests incorporate memory assessment as part of the assessment of intelligence, but memory can be impaired without a demonstrated decline in intellectual ability. There are several scales of memory assessment, as well as scales that are designed to measure malingered memory problems, and different types of memory

Personality Traits
Psychologists have identified many different personality traits which are present in all people. Different combinations of personality characteristics contribute to the vast range of individual differences we observe among people. Some personality tests are designed to describe personality differences among "normal" individuals, while others are designed to identify abnormal patterns of personality, and still others are designed to identify specific "personality disorders" according to diagnostic characteristics. Personality assessment can be important in as varied settings as the selection of people for different types of jobs, in determining psychological treatment needs, and in the assessment of criminals.

Pathological Psychological Problems
Some psychological tests identify individuals with serious psychological problems. These tests have been used in various settings, including security screening, criminal sentencing, child custody decisions and police selection, to name a few. Psychological tests exist to measure Depression, Anxiety, Paranoia, Psychopathic Deviance, Schizophrenia, Personality Disorders, and many other clinical conditions.

Life Stress Issues
Psychologists can assess the effects of stress on different individuals in various settings, which can be used to identify people who will need additional help to manage certain problems.

Neuropsychological Problems
Psychologists can identify the extent of brain damage suffered during a trauma by measuring the behavioral deficits and personality changes that have developed. These tests can provide valuable information about the extent of injuries to the brain, as well as providing a direction for rehabilitation for individuals with brain injuries.

Relationship Conflicts
Relationship conflicts often result from competing personality styles, differences in values or differences in attitudes. Psychologists can administer tests to couples which will highlight potential problem areas in a relationship. This is a valuable aid when helping couples resolve relationship problems.

Sensori-motor Problems
Some types of brain injuries and malignancies produce unusual sensory problems. Psychologists have developed assessment scales to identify these sensory problems. These test results can help plot the course of an illness, or can measure progress in cognitive rehabilitation.

Motivational Factors
"Why we do what we do" is an important question for employers, retailers, corrections psychologists, judges and individuals facing important life decisions. Psychologists have developed tests of motivation which help to identify what is important to different people in predicting or influencing their behavior.