The ability to think abstractly is certainly an important component of intelligence, and particularly in mathematics and theoretical physics where symbolism requires a strong connection between and understanding of a “concrete” reality and its representation. However there are several cognitive skills such as pattern recognition and a strong short-term memory that are also essential in supporting reasoning.
Intelligence contains many sub-competencies. The flow chart below from Intelligence, IQ and Perception, displays the cognitive abilities sub-tests on the WAIS III IQ test that measure both performance IQ (essentially, the abilities that underpin fluid intelligence) and verbal IQ (the abilities that underpin crystallized intelligence).
Abstract thinking is represented mostly by the cognitive skills under Performance IQ, and these tend to be major components of fluid IQ and are strongest in early adulthood. The skills under Verbal IQ tend to develop more as we age and contribute to crystallized intelligence. See also: In what ways do memory and intelligence change as we age? – Intelligence and IQ
