The puzzles go like this: a subject is given three different words, such as age, mile and sand, and asked to think of a single word that can form a compound word or phrase with each of the three. (In this case, the answer is stone: stone age, milestone, sandstone.) The subject has 15 seconds to solve the question before a new puzzle appears. If he comes up with an answer, he presses the space bar on the keyboard and says whether the answer arrived via insight or analysis.
Beeman teamed up with John Kounios, a psychologist at Drexel University. The first thing they discovered was that, although it seemed that the insight answer appeared out of nowhere, the brain had been laying the groundwork for the breakthrough. The process began with an intense mental search as the left hemisphere started looking for answers in all the obvious places. Because Beeman and Kounios were giving people word puzzles, they saw additional activation in brain areas related to speech and language. This left-brain thought process, however, quickly got tiring – it took only a few seconds before the subject said he’d reached an impasse and couldn’t think of the right word. But these negative feelings are actually an essential part of the process because they signal that it’s time to try a new search strategy. Instead of relying on the literal associations of the left hemisphere, the brain needs to shift activity to the other side, to explore a more unexpected set of associations.
What’s surprising is that this mental shift often works. Because we feel frustrated, we start to look at problems from a new perspective. “You’ll see people bolt up in their chair and their eyes go all wide,” says Ezra Wegbreit, a graduate student in the Beeman lab. The suddenness of the insight is preceded by an equally sudden burst of brain activity. Thirty milliseconds before the answer erupts into consciousness, there’s a spike of gamma-wave rhythm, which is the highest electrical frequency generated by the brain. Gamma rhythm is believed to come from the binding of neurons: cells distributed across the cortex draw themselves together into a new network that is then able to enter consciousness.
Where does this burst of gamma waves come from? Beeman and Kounios went back, analysed the data and discovered the “neural correlate of insight”: the anterior superior temporal gyrus (aSTG). This small fold of tissue, located on the surface of the right hemisphere just above the ear, became unusually active in the seconds before the epiphany. (It remained silent when people solved the word puzzles by analysis.) The activation of the cortical circuit was sudden and intense, a surge of electricity leading to a rush of blood.
Beeman argues that these linguistic skills share a substrate with insight because they require the brain to make a set of distant and original connections. Although most of us have probably never used age, mile and sand in a sentence before, the aSTG is able to discover the one additional word (stone) that works with all of them. And then, just when we’re about to give up, the answer is whispered into consciousness. “An insight is like finding a needle in a haystack,” Beeman says. “There are a trillion possible connections in the brain, and we have to find the exact right one. Just think of the odds!”
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