Definitions of intelligence are usually grouped into three families: the power to adjust to new conditions, the power to learn, and the power to think in abstract terms. The statement quoted here belongs clearly to the first family, because it makes adjustment to unfamiliar conditions the whole of the ability.

The adjustment view is associated with the German psychologist who also gave the ratio by which tested ability is compared with age. In his words intelligence is the general capacity of an individual consciously to adjust his thinking to new requirements, and it is this capacity for general mental adaptation to fresh problems and conditions of life.

The other names stand for different contributions. One writer defined the trait as the capacity for abstract thinking and standardised a widely used scale. Another worked with Binet on the first practical scale of ability. A third offered an educational definition centred on appropriateness of response rather than on adjustment to novelty.

Stern option is correct.