From decomposition to distributed theories of morphological processing in reading

MEG evidence for left temporal and orbitofrontal involvement in breaking down inflected words and putting the pieces back together

A major puzzle in the visual word recognition literature is how the human brain deals with complex words (e.g., presuppose). Prior work has shown that a multi-stage process is involved, starting with the early, form-based decomposition stage where a word is broken down into smaller pieces called morphemes {pre-}+{suppose} and ending with the recombination stages where the pieces are put back together to access the word's full meaning. However, most neurolinguistic studies have focused on the first stage, and/or on derivational morphology, which inherently carries both syntactic and semantic information, and this research has overwhelmingly investigated Indo-European languages. Here, we investigate visual word recognition of Tagalog complex words, focusing on inflectional prefixes which allows us to zero in on the contribution of syntactic information during the recombination stage, where both syntactic and semantic information are expected to be analyzed. Using MEG, we replicate previous findings implicating the left fusiform gyrus in segmenting complex words into pieces. We also show that the recombination stages, where the morphological pieces are put back together, activate the left posterior temporal lobe and left orbitofrontal cortex. Although our results support a multi-stage comprehension model of complex words and confirm that these distinct stages are associated with distinct spatiotemporal profiles, we also observed some spatiotemporal differences compared to previous studies on derivational morphology. For the first time, we show that inflected words activate the same core processing profile as derived words in the early (decomposition) stage, while later (recombination) stages of morphological processing point to an earlier and faster recombination of inflected words.

On humans' (explicit) intuitions about the meaning of novel words

Pseudowords offer a unique opportunity to investigate how humans deal with new (verbal) information. Within this framework, previous studies have shown that, at the implicit level, humans exploit systematic associations in the form-meaning interface to process new information by relying on (sub-lexical) contents already mapped in semantic memory. However, whether speakers exploit such processes in explicit decisions about the meanings elicited by unfamiliar terms remains an open, important question. Here, we tested this by leveraging computational models that are able to induce semantic representations for out-of-vocabulary stimuli. Across two experiments, we demonstrate that participants' guesses about pseudoword meanings in a 2AFC task consistently align with the model's predictions. This indicates that humans' ability to extract meaningful knowledge from complex statistical patterns can affect explicit decisions.

Cross-language morphological transfer in similar-script bilinguals

The current study explored cross-language morphological transfer mechanisms using a similar-script morphological translation priming paradigm in highly proficient unbalanced Turkish (first language; L1)-English (second language; L2) bilinguals. Using noncognate English and Turkish stimuli that shared a similar meaning with no form overlap (e.g., ice [Eng.] - buz [Tur.]), in Experiment 1, L2 English stem targets (e.g., ICE) were primed by affixed L1 nonwords (e.g., buzca [iceish]), nonaffixed L1 nonwords (e.g., buznak [iceald]), and unrelated L1 nonwords (e.g., tuşku [keyment]). The results revealed priming effects in both the affixed and nonaffixed nonword conditions relative to the unrelated control, and significantly larger priming in the affixed than the nonaffixed condition. In addition, enhanced cross-language morphological transfer effects were evidenced in bilinguals with an earlier age of L2 acquisition. In Experiment 2, English stem targets (e.g., ICE) were primed by nonaffixed L1 nonwords including translated stems (e.g., buznak [iceald]), semantically related stems (e.g., suzur [waterew]), and unrelated L1 nonwords (e.g., tuşzur [keyew]). The results showed significantly larger priming effects in the translated condition compared with the semantic and unrelated control conditions, with no priming in the semantic condition relative to the unrelated condition, suggesting that cross-language morphological priming effects were specifically due to the lexico-semantic relationship between the embedded word and its translation equivalent.

Malay Lexicon Project 3: The impact of orthographic-semantic consistency on lexical decision latencies

Theories of word processing propose that readers are sensitive to statistical co-occurrences between spelling and meaning. Orthographic-semantic consistency (OSC) measures provide a continuous estimate of the statistical regularities between spelling and meaning. Here we examined Malay, an Austronesian language that is agglutinative. In Malay, stems are often repeated in other words that share a related meaning (e.g., sunyi/quiet; ke-sunyi-an/silence; makan/eat; makan-an/foods). The first goal was to expand an existing large Malay database by computing OSC estimates for 2,287 monomorphemic words. The second goal was to explore the impact of root family size and OSC on lexical decision latencies for monomorphemic words. Decision latencies were collected for 1,280 Malay words of various morphological structures. Of these, data from 1,000 monomorphemic words were analysed in a series of generalised additive mixed models (GAMMs). Root family size and OSC were significant predictors of decision latencies, particularly for lower frequency words. We found a facilitative effect of root family size and OSC. Furthermore, we observed an interaction between root family size and OSC in that an effect of OSC was only apparent in words with larger root families. This interaction has not yet been explored in English but has the potential to be a new benchmark effect to test distributional models of word processing.

Automatic morpheme identification across development: Magnetoencephalography (MEG) evidence from fast periodic visual stimulation

The present study combined magnetoencephalography (MEG) recordings with fast periodic visual stimulation (FPVS) to investigate automatic neural responses to morphemes in developing and skilled readers. Native English-speaking children (N = 17, grade 5–6) and adults (N = 28) were presented with rapid streams of base stimuli (6 Hz) interleaved periodically with oddballs (i.e., every fifth item, oddball stimulation frequency: 1.2 Hz). In a manipulation-check condition, tapping into word recognition, oddballs featured familiar words (e.g., roll) embedded in a stream of consonant strings (e.g., ktlq). In the experimental conditions, the contrast between oddball and base stimuli was manipulated in order to probe selective stem and suffix identification in morphologically structured pseudowords (e.g., stem + suffix pseudowords such as softity embedded in nonstem + suffix pseudowords such as trumess). Neural responses at the oddball frequency and harmonics were analyzed at the sensor level using non-parametric cluster-based permutation tests. As expected, results in the manipulation-check condition revealed a word-selective response reflected by a predominantly left-lateralized cluster that emerged over temporal, parietal, and occipital sensors in both children and adults. However, across the experimental conditions, results yielded a differential pattern of oddball responses in developing and skilled readers. Children displayed a significant response that emerged in a mostly central occipital cluster for the condition tracking stem identification in the presence of suffixes (e.g., softity vs. trumess). In contrast, adult participants showed a significant response that emerged in a cluster located in central and left occipital sensors for the condition tracking suffix identification in the presence of stems (e.g., softity vs. stopust). The present results suggest that while the morpheme identification system in Grade 5–6 children is not yet adult-like, it is sufficiently mature to automatically analyze the morphemic structure of novel letter strings. These findings are discussed in the context of theoretical accounts of morphological processing across reading development.