Final answer:
The most common IQ test in use today is based on g-theory, which focuses on a general intelligence factor and was proposed by Charles Spearman. While other theories like the triarchic and Multiple Intelligences theories exist, they do not form the basis of the most widely used IQ test.
Step-by-step explanation:
The most common IQ test is based on g-theory, which refers to the general intelligence factor initially proposed by Charles Spearman. Spearman believed intelligence consisted of one general factor that could be measured and compared among individuals, focusing on the commonalities among various intellectual abilities.
In contrast to g-theory, Robert Sternberg developed the triarchic theory of intelligence, which divides intelligence into three components: practical, creative, and analytical. Meanwhile, Howard Gardner proposed the Multiple Intelligences Theory, suggesting individuals possess at least eight different intelligences, but this theory has been criticized for lacking empirical evidence. The widely used IQ test today, developed by David Wechsler, incorporates aspects of Spearman's g-theory, measuring an individual's ability to demonstrate a variety of cognitive abilities.