Psychology 101: Intro to Psychology

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We all want to be smart in one way or another, but what exactly is general intelligence? This lesson takes a look at the possible factors behind intellectual development and how this controversial topic has been examined by psychologists.

Few topics in psychology are as hotly debated or have as controversial a history as intelligence. The question of whether intelligence depends on biological or educational factors took a dark turn in the history of intelligence research. Many view intelligence as the human trait most directly related to success; so the stakes are high when psychologists set out to determine just how much control we have over our own intellectual development. Studies of intelligence have historically been used to justify discrimination, so modern researchers tackling the subject must be careful about research design and data interpretation.

In 1994, two American scholars published a best-selling, controversial book called The Bell Curve. The book proposes that intelligence is determined in part by genetics, and that African Americans and Latinos have genetically lower intelligence than Caucasians and Asian Americans. The authors also argue that since highly intelligent people tend to rise to the top of business and social circles, they're continually separating themselves as a class from less intelligent people. Their findings were rejected by many as a defense of race-based inequality, and as something that could be used to argue against programs designed to help historically underprivileged groups.

But how do we decide whether someone is intelligent or not? The Bell Curve relied extensively on standardized intelligence tests, but the accuracy and usefulness of these tests has been questioned since tests like this tend to favor people who are culturally similar to the test's designers. Is it possible to study intelligence in a way that doesn't inherently disadvantage one group or another?

Let's begin by attempting to define what intelligence truly is. Most people would agree that humans are smarter than other animals. But beyond that, how can we measure a person's intelligence compared to the rest of the population? Should intelligence be defined by the ability to do well in school, or instead in terms of common-sense street smarts; by the ability to solve problems, or to maintain emotional relationships? Are people who read lots of books smarter than people who can quickly pick up new forms of dance?

A broad, more inclusive definition of intelligence was proposed by a group of psychologists led by Ulric Neisser. They said that intelligence is the 'ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning and to overcome obstacles by taking thought.' According to Neisser and his colleagues, you're smart if you can succeed at a variety of interrelated tasks.

The work of psychologist Charles Spearman provides support for this idea. Spearman studied students' grades in various subjects. The statistical method Spearman used compares variability across multiple tasks, and is called factor analysis. Through factor analysis, Spearman found that high-performing students tend to do well across all subjects, not just in the subjects that they're especially strong in. So, an A student tends to get As in all subjects, but might earn an A+ in math because she's a math whiz.

Based on his findings, Spearman devised a 2-factor theory of intelligence. The first factor reflects the ability of the A student to get As in most subjects. Spearman called it the relatively constant level of mental performance across diverse mental tasks, or general global intelligence (g). Spearman's second factor, meanwhile, varies from task to task. This reflects the A+ in math that the A student gets because she's a math whiz. This type is known as specific intelligence (s), because it describes being smart in a specific way.

Most psychologists today believe that some version of general intelligence exists. Yet, the origins of intelligence, ways it can be measured and its importance for success in life are still being questioned.

You've learned that human intelligence is not fully understood. We still don't know what determines whether a person is smart, or how intelligence might best be measured. Nonetheless, many psychologists believe in the existence of a general intelligence, or a person's ability to think, reason, problem solve and complete a variety of tasks.