All psychologists are encouraged to take a scientific approach to their methodology. This means they have to study objectively. Psychologists, therefore, cannot measure things that have to be studied subjectively. For example, it would be difficult to measure emotions such as sadness because they cannot be measured by someone else objectively and it would be easier to measure objective variables such as reaction time.
There is also another factor that has to be taken into consideration when psychologists are studying. This is whether the variable they are studying is overt or covert. An overt variable may be a reaction time score or a memory recall score. These are overt behaviours as they are observable and they can be objectively measured by the psychologists. A covert variable would be sadness, for example, something which cannot be objectively measured by the psychologist.
These problems, however, can be solved using different methods. Psychologists can measure anything as long as it can be operationalised. This is when a researcher removes the ambiguity and defines the variable being measured it so that it can be measured and expressed quantitatively or qualitatively. Using the example of emotion, if a psychologist were to measure stress, they could use physiological measures such as heart rate or blood pressure (Cohen, 1983). The quantitative data collected could be used as a measure of stress. Problems of covert and subjective behaviors can also be measured using self report studies given by the psychologist (Bradley & Lang, 1994). This makes it possible for psychologists to measure variables such as emotions.
Intelligence is also difficult to measure objectively. The Binet-Simon intelligence scale, developed by French psychologists Alfred Binet and Theodore Simon, was administered to children to evaluate their intelligence/performance at a given age. They are given test item, puzzles etc in which they can receive scores on. The total score /IQ score rates the subject’s cognitive ability as compared to the general population.
To conclude, it is difficult for psychologists to measure covert and subjective variables, such as emotion, however it can be made possible by operationalising variables and by using self report studies.