NYC Gazette

When served a familiar caffeinated beverage at a local diner or cafe, the message “This coffee is hot” is clear. However, when told “This coffee is not hot,” the interpretation becomes ambiguous. A team of scientists has identified how our brains process phrases that include negation (i.e., “not”), revealing that it mitigates rather than inverts meaning.

“We now have a firmer sense of how negation operates as we try to make sense of the phrases we process,” explains Arianna Zuanazzi, a postdoctoral fellow in New York University’s Department of Psychology and lead author of the paper published in PLOS Biology. “In identifying that negation serves as a mitigator of adjectives—‘bad’ or ‘good,’ ‘sad’ or ‘happy,’ and ‘cold’ or ‘hot’—we also have a better understanding of how the brain functions to interpret subtle changes in meaning.”

Negation is often used intentionally in various communications, from advertising to legal filings, to obscure clear understanding. Additionally, large language models in AI tools struggle with interpreting passages containing negation. The researchers suggest their findings could improve AI functionality by showing how humans process such phrases.

Zuanazzi and her colleagues conducted experiments to measure participants' interpretations of phrases and monitored their brain activity during these tasks. Participants read adjective phrases with and without negation (e.g., “really not good” and “really really good”) on a computer monitor and rated their meaning on a scale from 1 (“really really bad”) to 10 (“really really good”). This was designed to determine if participants interpreted phrases with negation as opposite to those without it or as something more measured.

The researchers found that participants took longer to interpret phrases with negation than those without it, indicating that negation slows down our processing of meaning due to its complexity. Cursor movements showed that initially, negated phrases were interpreted affirmatively but later shifted to a mitigated meaning.

Magnetoencephalography (MEG) was used to measure the magnetic fields generated by participants' brain activity during these tasks. Neural representations of polar adjectives like “cold” and “hot” became more similar through negation, suggesting meanings like “not hot” are interpreted as "less hot" rather than "cold."

“This research spotlights the complexity that goes into language comprehension,” observes Zuanazzi, now at the Child Mind Institute.

The paper’s other authors include Pablo Ripollés from NYU’s Department of Psychology; Jean-Rémi King from France’s École Normale Supérieure; Wy Ming Lin from the University of Tübingen; Laura Gwilliams from NYU; and David Poeppel from NYU’s Department of Psychology and Ernst Strüngmann Institute for Neuroscience in Frankfurt, Germany.

The research was supported by a grant from the National Science Foundation (2043717).

Photo credit: Bill Chizek/Getty Images