When a bank becomes a bank, and a bank is the bank but not the bank: Multistability of homonyms’ meaning

Perceptual multistability is well-known and mostly visually demonstrated: Common examples are Necker's cube or Rubin's face-vase that produce qualitatively different percepts continuously oscillating between the solutions despite physically stable stimuli. We lack knowledge about similar phenomena in other domains, for instance in linguistics, where we are faced with homonyms that create multistability of cognitive semantics, differently assigned meanings of identical words. Our participants listened to repeated presentations of homonyms for which two or even three meanings could be assigned, and they reported the dominant meaning perceived at a certain point in time. Results showed that most participants experienced multistability of meaning for homonyms, with semiperiodic changes in dominant meaning similar to multistabity in perception. These findings suggest that multistability is a general property of the brain's neural architecture that resolves ambiguity irrespective of the level of representation.

. A selection of words used in the study, their assumed meaning(s), and translation to English (in blue). Word frequencies are reported on a scale from 1 (rare) to 6 (frequent) (DWDS, 2023).
Building on the multistability of perception, one can construct ambiguous images that produce changes in both perception and meaning, as in classic old-young woman (Donaldson, 2017) or duckrabbit (Donaldson, 2016) drawings. But can we take it even further to produce multistability of meaning alone, while the physical stimulus and the respective sensory signal remain constant? We looked at the ambiguity of homonyms, words with the same spelling and pronunciation, i.e., words that are both homographs and homophones. For example, in English, "the bank" could refer to a financial institution, but also to a riverbank, and "rock" could refer to a stone and a music genre. We used 20 German homonyms plus five control items with just a single dominant meaning, that is, nonhomonyms (Table 1). The study consisted of 25 trials (one trial for each word) and a test run. In each trial, we presented an audio recording of the respective word that was repeated 30 times over a period of approximately one minute. Participants had to indicate the perceived meaning and could also report "None" if they perceived no meaning, as semantic satiation can occur when hearing a word repeatedly (Jakobovits & Lambert, 1962;Wetherill, 2014). Twenty-two participants completed the experiment, see https://doi.org/10.17605/OSF.IO/JM8GE for open methods, data, and analysis.
We found that the repetition of homonyms induced switching between different dominant meanings, similar to alternations in perception during visual multistability, see Figure 1. Words differed greatly in the relative dominance of meaning, with words like Absatz or Decken showing balanced bi-and tristability, whereas words like Ball or Gut effectively had a single dominant meaning. The individual dominance phases were long even for balanced bistable stimuli with a single phase lasting for dozens of seconds.
Our results extend the list of multistable domains by demonstrating that the processing of homonyms shows similar effects to well-documented multistable stimuli. This provides further support for the idea that multistability is a general property of the brain's neural architecture that resolves any kind of ambiguity. For visual stimuli, this competition can occur at various levels of visual hierarchy, in our case of cognitive semantics, competition occurs at the cognitive level of words' meaning. However, conceptually similar mechanisms have been postulated at the level of decisionmaking both for perceptual decisions (Gold & Shadlen, 2007) and for delay discounting decisions (Scherbaum et al., 2016).
Taken together, this reinforces the idea that multistability is not a perceptual phenomenon per se but reflects computations of local but architecturally similar circuits that resolve ambiguity and support decision-making in a volatile world (Cao et al., 2021). Viewed from this angle, perceptual multistability induced by visual stimuli is merely a most convenient way to study the underlying neural mechanisms, rather than being an end in themselves. And, as the phenomenon of multistability is linked to the architecture of underlying circuits, it should manifest itself whenever we are able to supply balanced ambiguous inputs for such a circuit. In the present work, we employed words with different meanings, but further examples are likely to be discovered.
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