VOLUME LXIV | APR 2022

Easy does it: sequencing explains the in-out effect

In a recent study, researchers explore the perplexing phenomenon known as the in-out effect in speech articulation. They observe that speakers have a strong preference for words with consonant or syllable sequences that move from front to back in the mouth. Conversely, sequences that move from back to front are less favored. The scientists are fascinated by this phenomenon but find it inexplicable. They have investigated several theories, including connections to food consumption, fluency, and preferences for consonants produced at the front of the mouth, but none have yielded conclusive results. The underlying research invites readers to delve into the intricacies of speech patterns and discover potential explanations for the intriguing in-out effect.

Li Wei Chen

Li Wei is a Chinese-Canadian neuroscientist in Vancouver, studying brain plasticity and lifelong learning. He contributes articles on harnessing neurotechnology to expand human capabilities, drawing from his experiences in cross-cultural innovation hubs.

Ingendahl et al. [1] describe recent work on the in-out effect in articulation with the express purpose of engaging others in trying to solve its mysteries. The effect is that speakers prefer words with consonant or syllable sequences that proceed from front to back in the mouth, such as madiko, over those that go from back to front, such as kadimo. For Ingendahl et al. the in-out effect is inexplicable; various hypotheses relating it to food ingestion, fluency, and preferences for consonants produced in the front of the mouth are all described as dead ends.
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