If you've been called smart or intelligent your whole life, it may be for any of the reasons listed below. That's according to science, of course.

And if the verdict is still out on whether you're truly smart, this may just make your day. Perhaps you've been a genius in disguise the whole time. Well, not anymore.

How can you tell you're smart? Let me ask you:

1. Are you thin?

2006 study published in the Neurology journal found that people with a Body Mass Index--a measure of body fat--of 20 or less could recall 56 percent of words in a vocabulary test, while heavier subjects (with a BMI of 30 or higher) could remember only 44 percent. When retested five years later, obese subjects' cognitive recall dropped to 37.5 percent, whereas their thinner counterparts retained their level of recall.

2. Are you a leftie?

As reported in The New Yorker in 2013, psychiatrists from the University of Athens determined that lefties have faster and more accurate spatial skills, mental flexibility, and enhanced working memory. They're also "divergent thinkers"-- a specific kind of creativity that gives lefties the ability to generate novel ideas on a whim.

3. Are you an introvert?

The Gifted Development Center says that 60 percent of gifted children are introverted. As they grow into adulthood, they leverage their strength for processing and thinking things over, which is a trait of highly intelligent people. In fact, more than 75 percent of people with an IQ above 160 are introverted.

4. Were you breastfed?

A rather unorthodox study in Brazil followed 6,000 people from birth to the age of 30. Breastfed babies did better than babies who were nursed for a month or less, scoring better on intelligence tests as adults, having more success, and earning more.

5. Are you naturally curious?

Harvard Business Review reports that people with a higher "curiosity quotient" (CQ) are more inquisitive and generate more original ideas, and this "thinking style" leads to higher levels of knowledge acquisition over time. The author states that CQ "is the ultimate tool to produce simple solutions for complex problems."

6. Do you talk to yourself?

If you do, you're not crazy, just super smart. Science says that people who talk to themselves are able to define their problem more clearly and come up with a better solution more quickly than their silent counterparts. 

7. Are you the oldest sibling?

A study of 250,000 Norwegians published in Science magazine found that the oldest child in a family had an average IQ 2.3 points higher than younger siblings. The reason is due to environment and family dynamics, not genetics. The firstborn gets the benefits of full parental attention. When No. 2 arrives, that older sibling becomes a tutor to the younger sibling, which has high cognitive demands and boosts intelligence for some firstborns.

8. Are you a musician?

A growing body of evidence suggests that musicians have structurally and functionally different brains compared with nonmusicians. The research suggests that "the areas of the brain used to process music are larger or more active in musicians. The brain regions involved in music processing are also required for other tasks, such as memory or language skills."

9. Are you adaptable?

Intelligent people adapt better than others to changing circumstances by showing resilience. Research states that intelligent people are able to change their own behaviors in order to cope more effectively with their environment, or make changes to the environment they're in.

10. Do you have high self-control?

Scientists have found a link between self-control and intelligence. In one 2009 study, published in the journal Psychological Science, participants had to choose between two financial rewards: a smaller payout immediately or a larger payout at a later date. Those who exerted self-control and chose the larger payout at a later date generally scored higher on intelligence tests. 

11. Do you procrastinate?

Using a famous procrastinator, Steve Jobs, as an example, Wharton psychologist Adam Grant suggests that procrastination is key to innovation. Grant tells Business Insider, "The time Steve Jobs was putting things off and noodling on possibilities was time well spent in letting more divergent ideas come to the table, as opposed to diving right in with the most conventional, the most obvious, the most familiar."