People vary widely in their talents and skills. Some people are very good at schoolwork, which is often reflected in their IQ scores. Watch this lesson to find out more about IQ scores, including mental age and the bell curve distribution.
Claire has always been a bright girl. She understands things really quickly and does really well in school. Recently, she and her classmates took an IQ test at school, and Claire got a 115. But her parents wonder what that means. Is she a genius or just average?
Intelligence is defined in many different ways. Often, it is related to problem-solving and thinking skills. For example, if you give Claire a riddle, she can almost always figure it out. Some psychologists stress that there are multiple different intelligences, like the ability to get along well with others or the ability to understand and control one's own body.
But for the purposes of intelligence testing, or measuring one's intelligence through an assessment, intelligence is usually defined as a propensity for scholarship. In other words, most intelligence tests measure how well a person is likely to do in school. Because it is about scholastic aptitude, intelligence testing is not usually applicable to adults.
For example, if Claire does really well on an intelligence test, it would mean that she was likely to do really well in school. If she did not-so-well on the intelligence test, then she'd probably do not-so-well in school. Let's look closer at IQ, what an IQ score means, and how different people have different scores.
Remember that Claire has an IQ of 115. But, what does that mean? What is IQ, and is a score of 115 really, really good or really, really bad?
IQ stands for intelligence quotient, which is a score based on an intelligence test. Remember that we said that intelligence tests measure how well a person is likely to do in school, so that's what a person's IQ measures: his or her ability to get good grades in subjects like English and math.
The average IQ score is 100, which means that Claire is above average. That's great news! But, does that also mean that she's a better person than other kids, or that she's better at everything?
No! Remember that some psychologists believe that there are multiple intelligences, like interpersonal, kinesthetic, or musical intelligence. All an IQ can tell Claire and her parents is that she is above average in her ability to do well in school.
Sometimes, people talk about a person's mental age, or a person's ability expressed as the age at which most people reach that ability. If that sounds confusing, think about it like this: if Claire answers a bunch of questions that are commonly answered correctly by 10-year-olds, then her mental age is ten.
If Claire was born ten years ago, having a mental age of ten means that she's average. But if her chronological age, or the number of years a person has lived, is only eight, then she's two years ahead of where she is expected to be; that is, her chronological age is eight, but her mental age is ten. That's a good thing!
Of course, the opposite could be true, too. If Claire isn't very good in school, she might score low on an IQ test. Then, her mental age might be six. Her chronological age hasn't changed; she's still lived for eight years. But her mental age is now lower than her chronological age, indicating that she might struggle in school.
Bell Curve Distribution
All that mental age stuff is nice and all, but Claire's parents what to know what her IQ of 115 means in terms of other people. Is their daughter a genius or not so smart after all?
IQ scores vary widely. Some people might get a 115 or even a 150, while others might only get a 55 or 60. If you took the IQ of every single person in the world and plotted them on a graph, you'd get what's called a bell curve distribution, or a graph that has a big, rounded peak that tapers off on either end. It's called a 'bell curve' because it's the same shape as a bell.
Remember that we said that the average IQ is 100? No matter what age you are, the mean, median, and mode (all measures of what's normal or average) are all at 100 on the IQ distribution. That is, if we had one graph for 8-year-olds, and another for 18-year-olds, and another for 80-year-olds, the average for all of those graphs would be 100.
How is that possible? 100 isn't the percentage that a person got right. Instead, a person's raw score on an IQ test is converted into an IQ score, which is a score somewhere on the distribution. Say Claire gets right the questions that an average 8-year-old would get right. Her IQ score would be calculated as 100.
If she gets some questions that are harder right, her IQ score would be calculated as being higher than 100, like 115. On the other hand, if she gets some easier questions wrong, she would move down the bell curve, and her IQ score would be lower than 100, like 85. The point is that the average IQ score at any age is 100, and that means that about half of the people are above it and about half of them are below it.
Of course, some people are very far above or below it. A genius IQ is usually considered to be one at or above 145 because so few people get scores that high. On the other hand, someone is usually considered to have a mental disability if their IQ score is at or below 70.
But whether Claire's IQ is 145 or just 45, she and her parents should continue to remind themselves that IQ only measures how well a person is likely to do in school. It is not (and should not be) the end-all, be-all of a person's talents and gifts.
In psychological measurement, intelligence is defined as scholastic aptitude. A person's intelligence quotient, or IQ, is the score they received from taking an intelligence test. Children's IQ scores are often expressed as a mental age, which is often different from their chronological age. Finally, IQ scores fall along a bell curve distribution, or a graph that looks like a bell, with an average IQ score being 100, genius scores at or above 145, and mental disability at or below 70.
Realize these goals as you complete the lesson:
- Define intelligence in terms of psychological measurement
- Understand what intelligence test and IQ scores are
- Indicate the difference in mental age and chronological age when testing intelligence
- Discuss the bell curve distribution of intelligence and identify the score ranges