Reading a road map upside-down, excelling at chess, and generating synonyms for the word "brilliant" may seem like three very different skills. But each is thought to be a measurable indicator of general intelligence, a construct that includes problem-solving abilities, spatial manipulation, and language acquisition. Intelligence, in the abstract, is typically considered a desirable trait for someone to possess, but how (and how much) it actually impacts our chances of career or relationship success has yet to be fully determined through research.
Though there is some debate among researchers on the best way to measure intelligence, those who study it generally agree that it can be captured by psychometric tests. But while the field has made significant strides over the past few centuries, it is still dogged by complicated questions—ranging from just how much IQ actually contributes to an individual's success and well-being, to how genes and the environment interact to generate intelligence, to why the average IQ score appeared to rise throughout the world during the twentieth century.