Concepts of measurement in psychology are particularly noteworthy for having encountered scepticism. While people have been happy to accept that psychological attributes can be compared, many are suspicious about the possibility of assigning numerical scores to such concepts. The earliest success stories in psychological measurement occurred in the realm of psychophysics, the area most closely linked to the physical sciences. ‘Measurement in the behavioural sciences’ explains that there are different high level purposes for which psychological measurement might be undertaken, and that these purposes require different kinds of procedures. It looks at some particular challenges of measuring the mind, including the measurement of sensation and of intelligence.