Letter chunk frequency does not explain morphological masked priming

Research on visual word identification has extensively investigated the role of morphemes, recurrent letter chunks that convey a fairly regular meaning (e.g., lead-er-ship). Masked priming studies highlighted morpheme identification in complex (e.g., sing-er) and pseudo-complex (corn-er) words, as well as in nonwords (e.g., basket-y). The present study investigated whether such sensitivity to morphemes could be rooted in the visual system sensitivity to statistics of letter (co)occurrence. To this aim, we assessed masked priming as induced by nonword primes obtained by combining a stem (e.g., bulb) with (i) naturally frequent, derivational suffixes (e.g., -ment), (ii) non-morphological, equally frequent word-endings (e.g., -idge), and (iii) non-morphological, infrequent word-endings (e.g., -kle). In two additional tasks, we collected interpretability and word-likeness measures for morphologically-structured nonwords, to assess whether priming is modulated by such factors. Results indicate that masked priming is not affected by either the frequency or the morphological status of word-endings, a pattern that was replicated in a second experiment including also lexical primes. Our findings are in line with models of early visual processing based on automatic stem/word extraction, and rule out letter chunk frequency as a main player in the early stages of visual word identification. Nonword interpretability and word-likeness do not affect this pattern.

Letter chunk frequency does not explain morphological masked priming

Research on visual word identification has extensively investigated the role of morphemes, recurrent letter chunks that convey a fairly regular meaning (e.g.,lead-er-ship). Masked priming studies highlighted morpheme identification in complex (e.g., sing-er) and pseudo-complex (corn-er) words, as well as in nonwords (e.g., basket-y). The present study investigated whether such sensitivity to morphemes could be rooted in the visual system sensitivity to statistics of letter (co)occurrence. To this aim, we assessed masked priming as induced by nonword primes obtained by combining a stem (e.g.,bulb) with (i) naturally frequent, derivational suffixes (e.g.,-ment), (ii) non-morphological, equally frequent word endings (e.g.,-idge), and (iii) non-morphological, infrequent word endings (e.g.,-kle). In two additional tasks, we collected interpretability and word-likeness measures for morphologically-structured nonwords, to assess whether priming is modulated by such factors. Results indicate that masked priming is not affected by either the frequency or the morphological status of word endings. Our findings are in line with models of early visual processing based on automatic stem/word extraction, and rule out letter chunk frequency as a main player in the early stages of visual word identification. Nonword interpretability and word-likeness do not affect this pattern.

A general-purpose mechanism of visual feature association in visual word identification and beyond

Writing systems are a recent cultural invention, which makes it unlikely that specific cognitive mechanisms have developed through selective pressure for reading itself. Instead, reading might capitalize on evolutionary older mechanisms that originally supported other tasks. Accordingly, animals such as baboons can be trained to perform visual word recognition. This suggests that the visual mechanisms supporting reading might be phylogenetically old and domain-general. Here we propose that if the human reading system relies on domain-general visual mechanisms, effects that are typically found within the domain of reading should also be observable with non-orthographic visual stimuli. To test this hypothesis, we systematically tested different types of visual material with the same experimental design. Subjects were passively familiarized with a set of composite visual items, and then tested in an oddball paradigm for their ability to detect novel stimuli. Some of these novel stimuli shared their statistical structure with the familiar items, and were found to be hard to detect in two experiments using strings of letter-like symbols; this replicates the well-known, and supposedly reading-specific, bigram effect. Crucially, in two further experiments we show that the same effect emerges with made-up, 3D objects and sinusoidal gratings. The effect size was equivalent across experiments, despite the use of radically different stimuli. These data suggest that a fundamental mechanism behind visual word learning also supports the learning of other visual stimuli, implying that such mechanism is general-purpose. This mechanism would enable the statistical learning of regularities in the visual environment.

Morphological priming of inflectional suffixes

Morphologically complex words are processed through their constituent morphemes during visual word recognition. While this has been primarily established through the stem priming paradigm, the role of shared affixes is more controversial. Also, most evidence on affix priming comes from derivation, while inflectional priming remains largely unaddressed. Here we present two lexical decision, masked priming experiments filling this gap. Taking advantage of the rich inflectional pattern of Slovene, we assessed inflectional suffix priming (mestam–HALJAM), and compared it to the well-established stem priming effect (haljov–HALJAM): while the latter is solid as expected, the former seems to be weak to non–existing. Results further indicate that there is no interaction between sharing a stem and sharing an inflectional suffix—neither stem nor suffix priming is boosted when primes and targets also share the other morpheme. These data indicate an important difference between stems, derivational affixes and inflectional affixes, which we consider in the context of models of visual word identification and information theory.

Masked morphological priming tracks the development of a fully mature lexical system in L2

Visual word identification is based on an early morphological analysis in one’s native language; how these mechanisms apply to a second language is much less clear. We recruited L1 Italian–L2 English speakers in a masked priming task where the relationship between prime and target was morphologically transparent, e.g., employer–EMPLOY, morphologically opaque, e.g., corner-CORN, or merely orthographic, e.g., brothel–BROTH. Critically, participants underwent a thorough testing of their lexical, morphological, phonological, spelling and semantic proficiency in their second language. By exploring a wide spectrum of L2 proficiency, we showed that this factor critically qualifies L2 priming. Genuine morphological facilitation only arises as proficiency grows; and opaque and orthographic priming shrink as L2 competence increases. Age of acquisition was also evaluated, and did not affect the priming pattern. Furthermore, we showed that L2 priming is modulated by sensitivity to probabilistic relationships between form and meaning. Overall, these data illustrate the trajectory towards a fully consolidated L2 lexicon, and show that masked priming is a key tracker of this process.

Semantic and morphological cross-word priming during sentence reading

Our current understanding of visual word identification is difficult to extend to text reading—both experiments and theories focus primarily, if not exclusively, on out-of-context individual words. Here, we try to fill this gap by studying cross-word semantic and morphological priming within sentences in a natural reading, eye tracking experiment. We find that words are skipped more when they are preceded in the sentence by semantically related primes. Also, cross-word semantic priming manifests itself in later (e.g., gaze duration), but not in earlier (e.g., first-of-many fixations) indexes of eye movement on the target words. We also find that semantic priming is not modulated by the morphological agreement between primes and targets; and that morphological agreement does not yield any priming per se. These results point to independent lexical-semantic and morphological processing during sentence reading, and suggest cross-word reset for the latter, but not for the former.