A multifactorial model of the structure of intellect (SOI) developed and refined from 1946 onwards by the US psychologist J(oy) P(aul) Guilford (1897–1987) and usually depicted as an object loosely called a cube. According to the theory, intelligence comprises 120 independent abilities, extended in 1982 to 150. In the extended version of the theory, a given mental task may involve any of five possible kinds of mental operations (cognition, memory, divergent production, convergent production, or evaluation); five different kinds of mental representations or contents (visual, auditory, symbolic, semantic, or behavioural); and six different kinds of products (units, classes, relations, systems, transformations, or implications). Multiplying these together yields 150 different cognitive factors, each of which can be assessed by a different task, and the theory can be represented by a 5 × 5 × 6 ‘cube’ composed of 150 smaller units (see illustration). Also called the structure-of-intellect model. See also convergence-divergence, Merrill‐Palmer scale. Compare multiple intelligences.