Morpheme Ordering Across Languages Reflects Optimization for Processing Efficiency

Abstract

The ordering of morphemes in a word displays well-documented regularities across languages. Previous work has explained these in terms of notions such as semantic scope, relevance, and productivity. Here, we test a recently formulated processing theory of the ordering of linguistic units, the efficient tradeoff hypothesis (Hahn et al., 2021). The claim of the theory is that morpheme ordering can partly be explained by the optimization of a tradeoff between memory and surprisal. This claim has received initial empirical support from two languages. In this work, we test this idea more extensively using data from four additional agglutinative languages with significant amounts of morphology, and by considering nouns in addition to verbs. We find that the efficient tradeoff hypothesis predicts ordering in most cases with high accuracy, and accounts for cross-linguistic regularities in noun and verb inflection. Our work adds to a growing body of work suggesting that many ordering properties of language arise from a pressure for efficient language processing.

Information-theoretic applications to Hupa verbal morphology

“…This script also had the ability to shuffle morpheme order to use as a baseline. The measurement of MI and surprisal from the script is based on the equation in ( 7) (Hahn et al, 2021b). The first fraction represents the overall morpheme sequence probability within the training section of the corpus by dividing the frequency of the morpheme sequence 𝐹(𝑤 0 … 𝑤 𝑡 ) by the overall morpheme count in the training corpus |𝐶|.…”

“…Psycholinguistic experiments have observed correlations between surprisal and reading times (Monsalve et al 2012;Smith & Levy 2008) as well as pupil size (Frank & Thompson 2012). Hahn et al (2021b) utilized information theory to examine cross-linguistic morpheme order tendencies in the agglutinative languages Korean, Turkish, Japanese, Sesotho, Finnish, and Hungarian, specifically a verb affix ordering tendency observed by Bybee in (4) (1985a). The study utilized corpora that ranged from 2,735 (Hungarian) to 109,323 (Korean) verbal tokens.…”

“…This was also observed at the word level, where morphemes found closest to the root in linear distance were also highest in mutual information to the root on average, with a sharp drop off with increasing distance, seen in Figure 1 (right). The motivation for this phenomenon was proposed by Hahn et al (2021b) to be the memory-surprisal tradeoff, which states that placing mutually-informative morphemes closer together overall reduces the average surprisal the morpheme order has and thus maximizes information gain with smaller memory demands. As seen in Figure 2, Language A demonstrates a more efficient memory-surprisal tradeoff than Language B due to a morpheme order that is more aligned with information locality.…”

“…1. How can these information-theoretic methods of Hahn et al (2021b) be applied to a language like Hupa, given its low-resource nature and morphological intricacy?…”

The emergence of grammatical structure from inter-predictability

“…Futrell, Hahn and colleagues have identified various correlations, both with respect to specific constructions such as adjective stacking (e.g. beautiful green shirt versus ?green beautiful shirt) (Hahn et al, 2018), and more widely with respect to the proximity of words in phrase structure, and the proximity of affixes to the stem in word structure (Futrell, 2019;Hahn et al, 2021Hahn et al, , 2022. Pairs of morphemes (either words or affixes) are INTER-PREDICTABLE when they tend to co-occur in the same phrases, rather than independently.…”