Reading a road map upside-down and generating synonyms for the word "brilliant" are two very different skills. But each is a measurable indicator of general intelligence, a construct that includes problem solving abilities, spatial manipulation and language acquisition. Scientists generally agree that intelligence can be captured by psychometric tests.
Quite simply, cognition refers to thinking. There are the obvious applications of conscious reasoning—doing taxes, playing chess, deconstructing Macbeth—but thought takes many subtler forms, such as interpreting sensory input, guiding physical actions, and empathizing with others. The old metaphor for human cognition was the computer—a logical information-processing machine.