Who defined individual differences as 'the variations or deviations among individuals in regard to a single characteristic or a number of characteristics'?

'A child is average in achievement, high in intelligence, and low in scientific aptitude'. This variation across different traits within the same individual is an example of:

Consider the following descriptions: a) Variations or deviations found in a specific member of a group relative to the group's average concerning mental or physical traits. b) Differences observed across all psychological traits, including abilities, habits, and personality. Which option correctly relates these descriptions to educational concepts?