Negation via "not" in the brain and behavior

Two related articles about negation, courtesy of Victor Mair at Language Log:

Coopmans CW, Mai A, Martin AE (2024) “Not” in the brain and behavior. PLoS Biol 22(5): e3002656. https://doi.org/10.1371/journal.pbio.3002656

Negation is key for cognition but has no physical basis, raising questions about its neural origins. A new study in PLOS Biology on the negation of scalar adjectives shows that negation acts in part by altering the response to the adjective it negates.

Language fundamentally abstracts from what is observable in the environment, and it does so often in ways that are difficult to see without careful analysis. Consider a child annoying their sibling by holding their finger very close to the sibling’s arm. If asked what they were doing, the child would likely say, “I’m not touching them.” Here, the distinction between the physical environment and the abstraction of negation is thrown into relief. Although “not touching” is consistent with the situation, “not touching” is not literally what one observes because an absence is definitionally something that is not there. The sibling’s annoyance speaks to the actual situation: A finger is very close to their arm. This kind of scenario illustrates how natural language negation is truly a product of the human brain, abstracting away from physical conditions in the world

And here is the study:

Zuanazzi A, Ripollés P, Lin WM, Gwilliams L, King J-R, Poeppel D (2024) Negation mitigates rather than inverts the neural representations of adjectives. PLoS Biol 22(5): e3002622. https://doi.org/10.1371/journal.pbio.3002622

Abstract: Combinatoric linguistic operations underpin human language processes, but how meaning is composed and refined in the mind of the reader is not well understood. We address this puzzle by exploiting the ubiquitous function of negation. We track the online effects of negation (“not”) and intensifiers (“really”) on the representation of scalar adjectives (e.g., “good”) in parametrically designed behavioral and neurophysiological (MEG) experiments. The behavioral data show that participants first interpret negated adjectives as affirmative and later modify their interpretation towards, but never exactly as, the opposite meaning. Decoding analyses of neural activity further reveal significant above chance decoding accuracy for negated adjectives within 600 ms from adjective onset, suggesting that negation does not invert the representation of adjectives (i.e., “not bad” represented as “good”); furthermore, decoding accuracy for negated adjectives is found to be significantly lower than that for affirmative adjectives. Overall, these results suggest that negation mitigates rather than inverts the neural representations of adjectives. This putative suppression mechanism of negation is supported by increased synchronization of beta-band neural activity in sensorimotor areas. The analysis of negation provides a steppingstone to understand how the human brain represents changes of meaning over time.

I've not yet read the articles, but the issue has bothered me for a long time. Why? Because, to quote: "Negation is key for cognition but has no physical basis, raising questions about its neural origins."