This post was co-authored by Eileen Cardillo, D.Phil.
In the age of information overload, skimming the news is often one of the first things people do after wiping sleep from their eyes. Digital natives scroll through feeds. The slower-moving pour their coffee and open laptops. Within an hour, even most Luddites have unfolded a paper newspaper.
So begins the daily deluge of metaphors. A hundred and fifty years ago, Uncle Abe mended the good old Union with a few stitches. Recently, the Guardian reported that Stacey Abrams kicked off a campaign, No. 10 was furious at a leaked paper, and anti-abortion clinics were exploiting a loophole. Trump’s use of invasion to describe refugees at the border provokes a military response when a flood would suggest a need for humanitarian aid.
Your eighth-grade English teacher may have taught that metaphors liken two superficially dissimilar domains. This definition is inadequate for capturing the breadth and value of this linguistic trope. Metaphors come in many guises—abstracted verbs, refined adjectives, tweaked nouns. Even prepositions (especially prepositions) get in the game (what container do you occupy when you are in the mood, in a pickle, or in cahoots?).
An explicit comparison is more the exception than the rule. Broadly construed, metaphors use context to highlight a word’s abstract meaning, while muting its irrelevant concrete features. Despite their association with novelists and poets, we use metaphors all the time.
If metaphors are so common, why don’t we seem to notice them? Why do we rely on them so much?
The primary reason metaphors fly under our radar is that most metaphoric expressions are not new to our ears. Familiarity changes how we understand them. Words are typically polysemous—having many related meanings—but we effortlessly settle on their appropriate sense based on the context in which we encounter them.
For instance, as long as a person is familiar with cheetahs and humans, they will have no trouble understanding that "run" denotes a different form of motion when referring to one mammal than the other, and no motion at all when a refrigerator runs. With repeated exposure, a metaphoric sense is conventionalized and understood like any other.
A newly coined metaphor is more salient because it requires different cognitive work to derive its meaning. A listener must determine swiftly which semantic features of the metaphorically extended word are contextually relevant, and ignore those which are not.
Were tomorrow’s headlines to declare, “The rich lope through the recession,” efficient readers would suspend their usual association of a loping stride with quadrupeds. The peculiar agent of the verb (the rich) would signal against that habitual commitment, and the subsequent object (recession) would further restrict the verb’s relevant features, constraining its interpretation to imply the casual ease of the 1 percent rather than their actual gait. For the less familiar, applying these contextual constraints might require more effort.
Our lab and others have found that the feature-selection process obliged by novel metaphors increases the demands on our brain’s left-lateralized language network and semantic control areas in the bilateral prefrontal cortex. This shift in cognitive and neural processing is referred to as “the career of metaphor.” Most metaphors we encounter each day are long-term, dedicated employees, so reliable that we take for granted their meaningful work.
If familiar metaphors escape our attention, and novel ones tax it, then why do we use them so often? Because they deftly perform a variety of jobs. Metaphors are helpful didactic devices, using familiar domains to explain complex or new ones (e.g., technologies, scientific concepts, everything in sight to a toddler).
They can frame our thinking and attitudes. When having cancer is a battle, eventual winners and losers are involved; when it’s a journey, challenge and change are. An apt metaphor can also be an appealingly compact vehicle for conveying information. You can articulate the technical cascade underpinning the catastrophic, runaway consequences of a 2 degrees Celsius temperature increase for our overheating planet. Or, you can say the tipping point.
Some metaphors have aesthetic, as well as cognitive, functions. In literature and poetry, of course, writers use them to creatively express ideas, provoke empathy, and engage through imagery. Aesthetic considerations also apply in everyday speech and text. Metaphors may better capture attention than banal, literal expressions, sharpening nuance and tone when ably applied (which better describes the dizzying, dumbing thrill of falling in love—exciting or intoxicating?).
Most powerfully, metaphors enable us to think and converse about abstract and subjective experiences. Literal language is tethered to the sensory world. Metaphors extend our reasoning to encompass the intangible—the philosophical, emotional, and spiritual dimensions of human experience. They enrich thinking, stretch imaginations, and enhance interpersonal understanding.
The utility and frequency of metaphor belie its cognitive complexity. Metaphor is among the last verbal skills mastered in development. Such a flexible cognitive tool requires the engagement of many neural subsystems (working memory, semantic knowledge, reasoning, the theory of mind).
Fluid coordination of this neural activity is likely mediated by the prefrontal cortex, one of the last brain regions to mature and first to show age-related atrophy. In our own work, we have observed that older adults find metaphors more difficult to understand than closely matched, literal sentences, but young adults show no such discrepancy.
We have also found this gap between literal and metaphoric competence widens in patients with focal brain injuries in the left hemisphere. Traditional neural models of figurative language do not anticipate disproportionate or selective difficulty understanding metaphors in this population, but the pattern echoes figurative impairments in other neuro-atypical populations (schizophrenia, autism spectrum disorder, Alzheimer’s disease). Their consequences for social interactions and reasoning abilities are not yet known, and an important area for future research.
The capacity for metaphoric thought appears central to the uniquely abstract and flexible nature of our minds—and also particularly vulnerable to neural injury and disease. In language as in life, sometimes what is most precious to who we are is hardest to appreciate.
Cardillo, E. R., McQuire, M., & Chatterjee, A. (2018). Selective Metaphor Impairments After Left, Not Right, Hemisphere Injury. Frontiers in psychology, 9, 2308. https://doi.org/10.3389/fpsyg.2018.02308