Towards measuring lexical complexity in M alayalam (2019)

Abstract: This paper proposes a metric to quantify lexical complexity in Malayalam. The met- ric utilizes word frequency, orthography and morphology as the three factors affect- ing visual word recognition in Malayalam. Malayalam differs from other Indian lan- guages due to its agglutinative morphology and orthography, which are incorporated into our model. The predictions made by our model are then evaluated against reac- tion times in a lexical decision task. We find that reaction times are predicted by frequency, morphological complexity and script complexity. We also explore the interactions between morphological com- plexity with frequency and script in our results. To the best of our knowledge, this is the first study on lexical complexity in Malayalam.

## introduction the task of visual word recognition is related to language processing at the level of a word/lexical item. a word can be analyzed at several linguistic levels, and the word recognition task helps us understand the role of these levels in relation to processing, memory and attention. in psycholinguistics, previous work on this topic focuses on understanding the individual variables that affect the lexical processing of words. if we can quantify the influence of variables ranging from orthographic features to semantic factors on the cognitive processing of words, it would help us in understanding the critical factors underlying visual word recognition (and pattern recognition, more generally). the resulting model of word recognition can be evaluated against human judgements. models of word recognition are especially relevant for eye-tracking studies, where they have been extensively explored @xcite . word recognition models have also been used to understand reading disabilities such as phonological and surface dyslexia @xcite . for these studies, it is crucial to tease apart the effect of various factors that affect the task of reading. previous research has shown that the eye gaze duration is affected by frequency, orthography, morphology and phonology, among others. apart from these studies, an understanding of lexical complexity is also an interesting topic for study on its own. in this paper, we explore the case of malayalam and in particular examine three factors that could predict word complexity in the language: frequency, orthography and morphology. the role of variables that determine word recognition in malayalam has not been explored, as it has been for hindi @xcite . quantifying these factors in a model of lexical complexity can help us in developing norms that are useful in areas such as reading studies and word generation for lexical decision tasks. further, this would contribute towards cross-linguistic comparison of these factors from a different language family. to the best of our knowledge, this is the first work that examines lexical complexity in malayalam. ## lexical complexity the task of visual word recognition involves the cognitive processing of visual information and comparing it with a particular internal mental representation of a word. this representation itself may be at the graphemic, phonemic, morphemic and lexical semantic level, all of which have been shown to affect word recognition @xcite . in the sections that follow, we describe the three factors that are included in our study. ## method in order to compute the lexical complexity metric, token frequency, morphology and orthography were included as our variables. below, the methods for computing the values for each of these variables are discussed. ## results the trials belonging to those who scored below 70% in word-non-word accuracy were excluded, which brought the number of participants to 35. we fit a linear model using the lm function in r. log reaction times were used with frequency, script and morph as the covariates. figure 2 shows that the three variables are not highly correlated in our test set. ## discussion our results replicate the robust effects of frequency on lexical processing in malayalam. as frequency is a known predictor of reaction times, we expected to find a significant effect for frequency, but we particularly wanted to understand the effect of morphology and orthography on word recognition in malayalam. orthographic complexity as captured by diacritic placement and ligatures also has a significant effect on lexical processing. similarly, we also find an effect for morphological complexity in terms of the number of morphemes in a word. the interactions in our model point to an interesting relationship between high frequency words and morphological complexity. it appears that the effect of frequency cost becomes more pronounced in more complex words. in other words, low frequency words lead to higher reaction times particularly when they are morphologically complex. perhaps this is because the cost of lexical decomposition is higher in these words. on the other hand, the effect size of script is weaker and becomes visible only when the word is morphologically simple. when the word is morphologically complex, this effect is not very apparent. this work points to many interesting future avenues for exploring lexical complexity in an agglutinative language like malayalam. particularly, the effect of morphological complexity on factors like frequency need to be explored more thoroughly. in the future, we plan to carry out experiments with a larger set of items for the lexical decision task, as this was a preliminary study. we also plan to experiment with other measures of morphological complexity that take into account information about the type as well as the number of morphemes.