What is IQ?
Historically, IQ has been considered a representation of a person's intelligence. In fact, IQ stands for Intelligence Quotient, showing its relation to an idea of intelligence.
However, IQ today is not what most people think, so I want to help clear up how we conceptualize IQ now.
To start, there is no agreed upon definition of what constitutes "intelligence." There have been many different theories proposed, and most suggest that there are many forms of intelligence rather than one overarching intelligence. Ultimately, there is no way to reduce a person's "intelligence" down to a single number.
So then why are we still using an "Intelligence Quotient"? The acronym has remained primarily due to tradition and the desire to maintain a common language (from what I understand). "IQ" does not truly represent an "Intelligence Quotient" anymore. Instead, it is considered an overall approximation of a person's current capabilities within a set of specific domains, compared to others the same age.
In fact, many of us who work with assessment tools that provide an overall (or "Full Scale") IQ are not very interested in the final IQ score. Instead, we are interested in the person's performance across various domains (e.g., Processing Speed, Working Memory, Verbal Comprehension, Visual Spatial abilities) that generally represent "cognitive abilities." Even when looking at these broad domains, we typically look at the actual tasks that make up those domains, and we draw conclusions about a person's current strengths and weaknesses based upon the skills required for those tasks. After all, every task requires many different skills, so we cannot say performance on a single task fully represents a certain ability and we need to identify patterns.
In addition, IQ (and scores in the specific domains) are only approximations, and it is understood that scores can fluctuate from day-to-day. "Normal" performance also covers a wide range of scores, with 85-115* being considered the broad average range (so no, having an IQ that is 5 points higher than someone else generally isn't very meaningful).
As you may have noticed, I have been emphasizing that these scores are a representation of current abilities. That's because IQ (and performance in other domains) is not considered permanent, and scores can go up or down over time as a person's strengths and weaknesses change.
So what is IQ? It is not an absolute measure of overall intelligence. It does not represent how capable a person will be for the rest of their life. It does (to some extent) represent current abilities in a select list of domains. But it only represents one piece of the puzzle when considering a person's abilities, and it should not be given the weight that many people feel it deserves.
If you see something that is meant to estimate your IQ, then please, keep in mind that the number does not have much meaning by itself.
Have thoughts about IQ? Have questions about how we conceptualize cognitive abilities? Let me know in the comments!
*The average score is intended to be 100, with a standard deviation of 15.