Many people think that intelligence, like height, is an attribute that can be mapped onto a scale so that for any two people one can be identified as smarter than the other. However, intelligence unlike height, is a multi-faceted attribute. This means that A may be smarter than B in one aspect of intelligence, but B may be smarter than A in another. (Mathematicians would say that classification of people by height yields a linearly-ordered set, while classification of people by intelligence is a partially-ordered set.)
For example, Einstein had more insight into the natural laws governing the universe, than his friend and fellow student, Marcel Grossman. However, Grossman was a much better mathematician. Which of the two was smarter? Einstein was a smarter physicist; Grossman a smarter mathematician.
The best measure of intelligence that we have is the IQ test. On her IQ test, Marsha registered an IQ of 130, indicating that she had performed better than 97.7% of the people who took the same test. Kyle had an IQ score of 120, indicating that he performed better than 90.9% of the people who took the same test. Since Marsha scored higher than Kyle, does this prove she is smarter than Kyle?
Although IQ tests provide the best estimate of intelligence that we have, they are not able to measure long-term problem solving ability, creativity, imagination and a host of other cognitive qualities. Many people who do well in mathematics olympiads do not go on to solve the toughest problems in mathematics, while some of the greatest mathematical problem solvers do not do well in math olympiads. Marsha did better than Kyle on the IQ test, suggesting that she is “smarter” in some of those things measured by the test, but Kyle might be “smarter” in other types of tasks not measured by IQ tests.
In spite of this limitation of IQ tests, they are highly correlated with SAT’s and success in school However, correlations deal with averages. In individual cases there can be a significant difference between a person’s IQ score and their intelligence. For a more detailed insight into this issue, comparing the intelligence of Einstein with that of John von Neumann, visit: Can we compare the intelligence of brilliant people? – Intelligence and IQ
In cases where one person is more intelligent than another in virtually all domains, it is possible to say “A is smarter than B.” However, when people are closer in intelligence, the question “Who is smarter?” must be expressed relative to a particular domain. That’s why we can never say that there is one human being who is smarter than everyone else in all domains. There is no “smartest person.”