This document discusses theories of intelligence and factors that influence it. It describes intelligence as involving cognitive abilities like learning, reasoning, and adapting. Early theories proposed general intelligence involving mechanical, musical and artistic abilities. Later theorists like Howard Gardner proposed multiple intelligences involving linguistic, logical-mathematical, musical, spatial, kinesthetic, interpersonal and intrapersonal abilities. The document also outlines characteristics of standardized intelligence tests like objectivity, reliability and validity in measuring what they are intended to measure. It notes that intelligence is influenced by what is invested into brain development.