Answer:
due more to heredity than environment
Step-by-step explanation:
Personality or intelligence quotient (IQ) is shaped by genes as well as by an individual's upbringing and surrounding environment. However, in recent time many scientists and researchers have succeeded to identify certain personality characteristics or attributes to some specific genes.
There is a reaction range to intelligence quotient according to many experimenters and Hereditary plays both an upper and lower limit in the IQ and the environment determine where this limits of IQ lies within this.
Thus in the context, a 15 point difference between Blaine and Reese is due to the heredity factor and not environment factor as they both come from identical background.
Hence the answer is --
due more to heredity than environment