As per psychologists, individual differences refer to -

Distinctiveness and variations among people's characteristics and behavior patterns

The correct answer is Option (3) → Distinctiveness and variations among people's characteristics and behavior patterns

Variability is a fact of nature, and individuals are no exception to this. They vary in terms of physical characteristics, such as height, weight, strength, hair colour, and so on. They also vary along psychological dimensions. They may be intelligent or dull, dominant or submissive, creative or not so creative, outgoing or withdrawn, etc. The list of variations can be endless. Different traits can exist in varying degrees in an individual. In this sense, each one of us is unique as s/he exemplifies a typical combination of various traits. The question which you may like to pose is how and why people differ. This, in fact, is the subject matter of the study of individual differences. For psychologists, individual differences refer to distinctiveness and variations among people’s characteristics and behaviour patterns.