Ellis, R. S. (1928). An analysis of the individual. In R. S. Ellis, The psychology of individual differences (pp. 52-73). New York, NY, US: D Appleton & Company.
http://dx.doi.org/10.1037/10973-003
Before we can hope to get very far in the discussion of individual differences, it is necessary for us to analyze the individual into different traits, tendencies, capacities, or other simpler and more elementary units, because an individual is far too complex to be discussed as a whole, and an attempt to compare different individuals without first making such an analysis would lead to considerable confusion. We shall, therefore, consider in what respects that would be significant for psychology one individual may differ from another. The significance of outer physical traits (body size, form and proportion, color of hair, skin and eyes) to psychology is addressed. Inner physical characteristics that are psychologically important (structure, balance, health, resistance, strength, metabolic ratio) are discussed. Native psycho-motor characteristics (motor capacities, sensory capacities, affect, reflexes, instincts, emotions, attention, imagery, imagination, perception, memory, association, reasoning, intelligence) and acquired psycho-motor characteristics (habits, skills, knowledge, purposes, ideals, meanings, attitudes, acquired motor reactions, mental unity) are described. (PsycINFO Database Record (c) 2016 APA, all rights reserved)