If you feel a little weary of social functions and prefer solo nights in to big group hangs, you can now back up your introverted inclinations with a classic psychological test. Psychologist Christian Jarrett recently shared the test in his new BBC column, and all you need to determine if you're an introvert is a lemon, a Q-tip, and some thread.

How it works.

The test — which personality expert Brian Little adapted from one created by 1960s personality psychology pioneers Hans and Sybil Eysenck — takes less than a minute and measures introversion in terms of a person's physical reaction to the taste of lemon juice.

Hans Eysenck believed that introverts were more responsive to external stimuli than extroverts because they perceived situations as more intense; this became the basis of his “cortical arousal” theory.

The Eysencks set out to test this by having participants taste a lemon and measured how much they salivated. They also administered a psychological questionnaire that measured introverted qualities. The results supported their hypothesis: Introverts salivated more than extroverts when they tasted something sour, and they also scored higher on the questionnaire. They believe that the increased salivation was therefore a heightened response to the stimuli of lemon juice.

The DIY lemon test is simple.

First you, tie a piece of thread around the middle of the Q-Tip. Then, put one end of the Q-tip on your tongue for 20 seconds.

Drop five drops of lemon juice on your tongue and swallow them.

Put the other end of the Q-tip of your tongue for 20 seconds.

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Hold up the thread. If the Q-tip hangs horizontally, the test suggests that you are extroverted, because both Q-tip ends had equal amounts of saliva. If the Q-tip hangs on a slant with the lemon-side lower, the difference between the ends' weights means are introverted.

Is it accurate?

Studies have shown that introverts respond more intensely to stimulation such as noise and caffeine, but as Jarrett pointed out in his column, not all researchers agree that salivation is a response to a stimulus that correlates to introverted personality traits.

In 1993, researchers from the University of Glasgow performed the lemon test on 36 male and female subjects and concluded that their salivary flow did not correlate to introversion or extroversion. They also looked at whether or not it was indicative of anxiety, and found that it was not.

Want that minute back? Jarrett points out that, at the very least, "it certainly does tell you something interesting about your physical sensitivity – and you could always try repeating it a few times to get a more reliable result."

Introversion can be measured in other ways.

Introverted and extroverted personality traits were first identified by seminal psychologist Carl Jung, Gizmodo pointed out. According to Jung, extroverts are energized by social situations, but introverts find them draining.

While arousal may be indicative of introversion and extroversion, it isn't the only contributing factor. Research has found that introverted and extroverted brains differ in numerous ways.

Many experts think that extroverts and introverts brains process dopamine differently.

In a 2013 study, subjects were given the stimulant Ritalin, which increases dopamine flow in the brain, and shown a series of videos. The researchers took the subjects off the drug after three days and observed that introverts responded less excitedly to the videos than extroverts did. This led the researchers to believe that extroverts linked the dopamine release of the Ritalin high to their environment, while the introverts did not.

"The findings could help explain why extroverts seek the high of a wild party, whereas introverts may prefer a quiet cup of tea at home," Live Science reported.

Research has also suggested different patterns of blood flow may shape the divergent ways introverts and extroverts think, perceive, and socialize.

A 1999 study used positron emission tomography (PET) scans to measure cerebral blood flow. "They found that the introverts had more blood flow in their frontal lobes and anterior thalamus — brain regions involved with recalling events, making plans, and solving problems," Gizmodo reported. "Extroverts had more blood flow in brain areas involved with interpreting sensory data, including the anterior cingulate gyrus, the temporal lobes and the posterior thalamus."

It's also worth noting that most psychologists believe that these qualities are a spectrum — everyone possesses both extroverted and introverted traits to some degree.

"There is no such thing as a pure introvert or extrovert," Jung said, according to Fast Company. "Such a person would be in the lunatic asylum."

[H/T Science of Us]