Nature of Psychological Data

Psychological data differ in important ways from the data collected in other sciences, so it is worth pausing on what 'data' actually means here. Data (plural of datum) refers to information about people's overt or covert behaviour, subjective experiences, and mental processes, gathered through a variety of methods from a variety of sources. Data are never free-standing facts; they are always tied to the particular context, the people involved, the time at which the behaviour occurred, the theory that guided the study, and the specific method used to collect them (survey, interview, experiment, and so on). The same person may behave quite differently when observed than when merely asked to describe their own behaviour, and differently again depending on who is present. Because of this, data never 'speak for themselves': a researcher must interpret them and place them within their proper context before they mean anything. Psychologists typically collect four broad types of information. Demographic information covers personal background details such as name, age, gender, birth order, education, occupation, marital status, family income and so on. Physical information covers the ecological and environmental context: terrain, type of economy, housing conditions, facilities available at home or school, mode of transport, etc. Physiological data covers measurable bodily indicators such as height, weight, heart rate, fatigue, Galvanic Skin Resistance (GSR), brain activity recorded through an Electro-encephalograph (EEG), blood pressure, sleep duration, and so on. Psychological information covers the core subject matter of the discipline itself: intelligence, personality, interest, values, creativity, emotion, motivation, psychological disorders, illusions, delusions, hallucinations, perceptual judgment, thought and consciousness. From a measurement standpoint, this last category of information tends to be compar …