Consonant Bias Research Articles

Infants' abilities to segment word forms from spectrally degraded speech in the first year of life.

Infants begin to segment word forms from fluent speech-a crucial task in lexical processing-between 4 and 7 months of age. Prior work has established that infants rely on a variety of cues available in the speech signal (i.e., prosodic, statistical, acoustic-segmental, and lexical) to accomplish this task. In two experiments with French-learning 6- and 10-month-olds, we use a psychoacoustic approach to examine if and how degradation of the two fundamental acoustic components extracted from speech by the auditory system, namely, temporal (both frequency and amplitude modulation) and spectral information, impact word form segmentation. Infants were familiarized with passages containing target words, in which frequency modulation (FM) information was replaced with pure tones using a vocoder, while amplitude modulation (AM) was preserved in either 8 or 16 spectral bands. Infants were then tested on their recognition of the target versus novel control words. While the 6-month-olds were unable to segment in either condition, the 10-month-olds succeeded, although only in the 16 spectral band condition. These findings suggest that 6-month-olds need FM temporal cues for speech segmentation while 10-month-olds do not, although they need the AM cues to be presented in enough spectral bands (i.e., 16). This developmental change observed in infants' sensitivity to spectrotemporal cues likely results from an increase in the range of available segmentation procedures, and/or shift from a vowel to a consonant bias in lexical processing between the two ages, as vowels are more affected by our acoustic manipulations. RESEARCH HIGHLIGHTS: Although segmenting speech into word forms is crucial for lexical acquisition, the acoustic information that infants' auditory system extracts to process continuous speech remains unknown. We examined infants' sensitivity to spectrotemporal cues in speech segmentation using vocoded speech, and revealed a developmental change between 6 and 10 months of age. We showed that FM information, that is, the fast temporal modulations of speech, is necessary for 6- but not 10-month-old infants to segment word forms. Moreover, reducing the number of spectral bands impacts 10-month-olds' segmentation abilities, who succeed when 16 bands are preserved, but fail with 8 bands.

Danish 20-month-olds' recognition of familiar words with and without consonant and vowel mispronunciations.

Although several studies initially supported the proposal by Nespor et al. (Nespor,Marina, Marcela Peña & Jacques Mehler. 2003. On the different roles of vowels and consonants in speech processing and language acquisition. Lingue e Linguaggio 2. 221-247) that consonants are more informative than vowels in lexical processing, a more complex picture has emerged from recent research. Current evidence suggests that infants initially show a vowel bias in lexical processing and later transition to a consonant bias, possibly depending on the characteristics of the ambient language. Danish infants have shown a vowel bias in word learning at 20months-an age at which infants learning French or Italian no longer show a vowel bias but rather a consonant bias, and infants learning English show no bias. The present study tested whether Danish 20-month-olds also have a vowel bias whenrecognizing familiar words. Specifically, using the Intermodal Preferential Looking paradigm, we tested whether Danish infants were more likely to ignore or accept consonant than vowel mispronunciations when matching familiar words with pictures. The infants successfully matched correctly pronounced familiar words with pictures but showed no vowel or consonant bias when matching mispronounced words with pictures. The lack of a bias for Danish vowels or consonants in familiar word recognition adds to evidence that lexical processing biases are language-specific and may additionally depend on developmental age and perhaps task difficulty.

Vowels and consonants matter equally to British English-learning 11-month-olds' familiar word form recognition.

While adult studies show that consonants are more important than vowels in lexical processing tasks, the developmental trajectory of this consonant bias varies cross-linguistically. This study tested whether British English-learning 11-month-old infants' recognition of familiar word forms is more reliant on consonants than vowels, as found by Poltrock and Nazzi (2015) in French. After establishing that infants prefer listening to a list of familiar words over pseudowords (Experiment 1), Experiment 2 examined preference for consonant versus vowel mispronunciations of these words. Infants listened to both alterations equally. In Experiment 3, using a simplified version of the task with one familiar word only ('mummy'), infants' preference for its correct pronunciation over a consonant or a vowel change confirmed an equal sensitivity to both alterations. British English-learning infants' word form recognition appears to be equally impacted by consonant and vowel information, providing further evidence that initial lexical processes vary cross-linguistically.

The roots of consonant bias in semitic languages: a critical review of psycholinguistic studies of languages with non-concatenative morphology

The roots of consonant bias in semitic languages: a critical review of psycholinguistic studies of languages with non-concatenative morphology

Consonant bias in adult lexical processing under acoustically degraded listening conditions.

Consonants facilitate lexical processing across many languages, including French. This study investigates whether acoustic degradation affects this phonological bias in an auditory lexical decision task. French words were processed using an eight-band vocoder, degrading their frequency modulations (FM) while preserving original amplitude modulations (AM). Adult French natives were presented with these French words, preceded by similarly processed pseudoword primes sharing their vowels, consonants, or neither. Results reveal a consonant bias in the listeners' accuracy and response times, despite the reduced spectral and FM information. These degraded conditions resemble current cochlear-implant processors, and attest to the robustness of this phonological bias.

Spanish-learning infants switch from a vowel to a consonant bias during the first year of life

The consonant bias is evidenced by a greater reliance on consonants over vowels in lexical processing. Although attested during adulthood for most Roman and Germanic languages (e.g., French, Italian, English, Dutch), evidence on its development suggests that the native input modulates its trajectory. French and Italian learners exhibit an early switch from a higher reliance on vowels at 5 and 6 months of age to a consonant bias by the end of the first year. This study investigated the developmental trajectory of this bias in a third Romance language unexplored so far—Spanish. In a central visual fixation procedure, infants aged 5, 8½, and 12 months were tested in a word recognition task. In Experiment 1, infants preferred listening to frequent words (e.g., leche, milk) over nonwords (e.g., machi) at all ages. Experiment 2 assessed infants’ listening times to consonant and vowel alterations of the words used in Experiment 1. Here, 5-month-olds preferred listening to consonant alterations, whereas 12-month-olds preferred listening to vowel alterations, suggesting that 5-month-olds’ recognition performance was more affected by a vowel alteration (e.g., leche →lache), whereas 12-month-olds’ recognition performance was more affected by a consonant alteration (e.g., leche →keche). These findings replicate previous findings in Italian and French and generalize them to a third Romance language (Spanish). As such, they support the idea that specific factors common to Romance languages might be driving an early consonant bias in lexical processing.

Consonant, vowel and lexical neighbourhood processing during word recognition: New evidence using the sandwich priming technique

ABSTRACT Studies on French adults using a written lexical decision task with masked priming, in which targets were more primed by consonant- (jalu-JOLI) than vowel-related (vobi-JOLI) primes, support the proposal that consonants have more weight than vowels in lexical processing. This study examines the phonological and/or lexical nature of this consonant bias (C-bias), using a sandwich priming task in which a brief presentation of the target (pre-prime) precedes the prime-target sequence, a manipulation blocking lexical neighbourhood effects. Results from three experiments (varying pre-prime/prime durations) show consistent C-priming and no significant V-priming at earlier and later processing stages (50 or 66 ms primes). Yet, a joint analysis reveals a small V-priming, while confirming a significant consonant advantage. This demonstrates the contribution of the phonological level to the C-bias. Second, differences in performance comparing the classic versus sandwich priming task also establish a contribution of lexical neighbourhood inhibition effects to the C-bias.

The role of linguistic experience in the development of the consonant bias.

Consonants and vowels play different roles in speech perception: listeners rely more heavily on consonant information rather than vowel information when distinguishing between words. This reliance on consonants for word identification is the consonant bias Nespor et al. (Ling 2:203-230, 2003). Several factors modulate infants' development of the consonant bias, including fine-grained temporal processing ability and native language exposure [for review, see Nazzi et al. (Curr Direct Psychol Sci 25:291-296, 2016)]. A rat model demonstrated that mature fine-grained temporal processing alone cannot account for consonant bias emergence; linguistic exposure is also necessary Bouchon and Toro (An Cog 22:839-850, 2019). This study tested domestic dogs, who have similarly fine-grained temporal processing but more language exposure than rats, to assess whether a minimal lexicon and small degree of regular linguistic exposure can allow for consonant bias development. Dogs demonstrated a vowel bias rather than a consonant bias, preferring their own name over a vowel-mispronounced version of their name, but not in comparison to a consonant-mispronounced version. This is the pattern seen in young infants Bouchon et al. (Dev Sci 18:587-598, 2015) and rats Bouchon et al. (An Cog 22:839-850, 2019). In a follow-up study, dogs treated a consonant-mispronounced version of their name similarly to their actual name, further suggesting that dogs do not treat consonant differences as meaningful for word identity. These results support the findings from Bouchon and Toro (An Cog 2:839-850, 2019), suggesting that there may be a default preference for vowel information over consonant information when identifying word forms, and that the consonant bias may be a human-exclusive tool for language learning.

Emergence of a consonant bias during the first year of life: New evidence from own-name recognition.

Recent evidence suggests that during the first year of life, a preference for consonant information during lexical processing (consonant bias) emerges, at least for some languages like French. Our study investigated the factors involved in this emergence as well as the developmental consequences for variation in consonant bias emergence. In a series of experiments, we measured 5-, 8-, and 11-month-old French-learning infants orientation times to a consonant or vowel mispronunciation of their own name, which is one of the few word forms familiar to infants at this young age. Both 5- and 8-month-olds oriented longer to vowel mispronunciations, but 11-month-olds showed a different pattern, initially orienting longer to consonant mispronunciations. We interpret these results as further evidence of an initial vowel bias, with consonant bias emergence by 11months. Neither acoustic-phonetic nor lexical factors predicted preferences in 8- and 11-month-olds. Finally, counter to our predictions, a vowel bias at the time of test for 11-month-olds was related to later productive vocabulary outcomes.

Is the consonant bias specifically human? Long-Evans rats encode vowels better than consonants in words.

In natural languages, vowels tend to convey structures (syntax, prosody) while consonants are more important lexically. The consonant bias, which is the tendency to rely more on consonants than on vowels to process words, is well attested in human adults and infants after the first year of life. Is the consonant bias based on evolutionarily ancient mechanisms, potentially present in other species? The current study investigated this issue in a species phylogenetically distant from humans: Long-Evans rats. During training, the animals were presented with four natural word-forms (e.g., mano, "hand"). We then compared their responses to novel words carrying either a consonant (pano) or a vowel change (meno). Results show that the animals were less disrupted by consonantal alterations than by vocalic alterations of words. That is, word recognition was more affected by the alteration of a vowel than a consonant. Together with previous findings in very young human infants, this reliance on vocalic information we observe in rats suggests that the emergence of the consonant bias may require a combination of vocal, cognitive and auditory skills that rodents do not seem to possess.

The consonant bias in word learning is not determined by position within the word: Evidence from vowel-initial words

The current study used an object manipulation task to explore whether infants rely more on consonant information than on vowel information when learning new words even when the words start with a vowel. Canadian French-learning 20-month-olds, who were taught pairs of new vowel-initial words contrasted either on their initial vowel (opsi/eupsi) or following consonant (oupsa/outsa), were found to have learned the words only in the consonant condition and performed significantly better in the consonant condition than in the vowel condition. These results extend to Canadian French-learning infants the consonant bias in word learning previously found in French-learning infants from France and, crucially, shows that vocalic information has less weight than consonant information in new word learning even when it is the initial sound of the target words, confirming the consonant bias at the lexical level postulated by Nespor et al. (2003). The current findings also suggest that French-learning infants are able to segment vowel-initial words as early as 20 months of age.

The Developmental Origins of the Consonant Bias in Lexical Processing

Consonants have been proposed to carry more of the weight of lexical processing than vowels. This consonant bias has consistently been found in adults and has been proposed to facilitate early language acquisition. We explore the origins of this bias over the course of development and in infants learning different languages. Although the consonant bias was originally thought to be present at birth, evidence suggests that it arises from the early stages of phonological and (pre-)lexical acquisition. We discuss two theories that account for the acquisition of the consonant bias: the lexical and acoustic-phonetic hypotheses.

Vowels, then consonants: Early bias switch in recognizing segmented word forms

The division of labor hypothesis proposed by Nespor, Peña, and Mehler (2003) postulates that consonants are more important than vowels in lexical processing (when learning and recognizing words). This consonant bias (C-bias) is supported by many adult and toddler studies. However, some cross-linguistic variation has been found in toddlerhood, and various hypotheses have been proposed to account for the origin of the consonant bias, which make distinct predictions regarding its developmental trajectory during the first year of life. The present study evaluated these hypotheses by investigating the consonant bias in young French-learning infants, a language in which a consistent consonant bias is reported from 11months of age onward. Accordingly, in a series of word form segmentation experiments building on the fact that both 6- and 8-month-old French-learning infants can segment monosyllabic words, we investigated the relative impact of consonant and vowel mispronunciations on the recognition of segmented word forms at these two ages. Infants were familiarized with passages containing monosyllabic target words and then tested in different conditions all including consonant and/or vowel mispronunciations of the target words. Overall, our findings reveal a consonant bias at 8months, but an opposite vowel bias at 6months. These findings first establish that the consonant bias emerges between 6 and 8months of age in French-learning infants. Second, we discuss the factors that might explain such a developmental trajectory, highlighting the possible roles of pre-lexical and phonological acquisition.

Vowel bias in Danish word-learning: processing biases are language-specific.

The present study explored whether the phonological bias favoring consonants found in French-learning infants and children when learning new words (Havy & Nazzi, 2009; Nazzi, 2005) is language-general, as proposed by Nespor, Peña and Mehler (2003), or varies across languages, perhaps as a function of the phonological or lexical properties of the language in acquisition. To do so, we used the interactive word-learning task set up by Havy and Nazzi (2009), teaching Danish-learning 20-month-olds pairs of phonetically similar words that contrasted either on one of their consonants or one of their vowels, by either one or two phonological features. Danish was chosen because it has more vowels than consonants, and is characterized by extensive consonant lenition. Both phenomena could disfavor a consonant bias. Evidence of word-learning was found only for vocalic information, irrespective of whether one or two phonological features were changed. The implication of these findings is that the phonological biases found in early lexical processing are not language-general but develop during language acquisition, depending on the phonological or lexical properties of the native language.

Call me Alix, not Elix: vowels are more important than consonants in own-name recognition at 5 months.

Consonants and vowels differ acoustically and articulatorily, but also functionally: Consonants are more relevant for lexical processing, and vowels for prosodic/syntactic processing. These functional biases could be powerful bootstrapping mechanisms for learning language, but their developmental origin remains unclear. The relative importance of consonants and vowels at the onset of lexical acquisition was assessed in French-learning 5-month-olds by testing sensitivity to minimal phonetic changes in their own name. Infants' reactions to mispronunciations revealed sensitivity to vowel but not consonant changes. Vowels were also more salient (on duration and intensity) but less distinct (on spectrally based measures) than consonants. Lastly, vowel (but not consonant) mispronunciation detection was modulated by acoustic factors, in particular spectrally based distance. These results establish that consonant changes do not affect lexical recognition at 5 months, while vowel changes do; the consonant bias observed later in development does not emerge until after 5 months through additional language exposure.

Tracking the emergence of the consonant bias in visual-word recognition: evidence with developing readers.

Recent research with skilled adult readers has consistently revealed an advantage of consonants over vowels in visual-word recognition (i.e., the so-called “consonant bias”). Nevertheless, little is known about how early in development the consonant bias emerges. This work aims to address this issue by studying the relative contribution of consonants and vowels at the early stages of visual-word recognition in developing readers (2nd and 4th Grade children) and skilled adult readers (college students) using a masked priming lexical decision task. Target words starting either with a consonant or a vowel were preceded by a briefly presented masked prime (50 ms) that could be the same as the target (e.g., pirata-PIRATA [pirate-PIRATE]), a consonant-preserving prime (e.g., pureto-PIRATA), a vowel-preserving prime (e.g., gicala-PIRATA), or an unrelated prime (e.g., bocelo -PIRATA). Results revealed significant priming effects for the identity and consonant-preserving conditions in adult readers and 4th Grade children, whereas 2nd graders only showed priming for the identity condition. In adult readers, the advantage of consonants was observed both for words starting with a consonant or a vowel, while in 4th graders this advantage was restricted to words with an initial consonant. Thus, the present findings suggest that a Consonant/Vowel skeleton should be included in future (developmental) models of visual-word recognition and reading.

English-learning one- to two-year-olds do not show a consonant bias in word learning

Following the proposal that consonants are more involved than vowels in coding the lexicon (Nespor, Peña & Mehler, 2003), an early lexical consonant bias was found from age 1;2 in French but an equal sensitivity to consonants and vowels from 1;0 to 2;0 in English. As different tasks were used in French and English, we sought to clarify this ambiguity by using an interactive word-learning study similar to that used in French, with British-English-learning toddlers aged 1;4 and 1;11. Children were taught two CVC labels differing on either a consonant or vowel and tested on their pairing of a third object named with one of the previously taught labels, or part of them. In concert with previous research on British-English toddlers, our results provided no evidence of a general consonant bias. The language-specific mechanisms explaining the differential status for consonants and vowels in lexical development are discussed.

The time course of consonant and vowel processing during word recognition

In a recent study using a masked priming lexical decision task, New, Araujo, and Nazzi found priming of targets by primes sharing consonants (jalu-JOLI) but not by primes sharing vowels (vobi-JOLI). To examine the orthographic or phonological/lexical nature of this consonantal bias, and to determine whether vocalic priming can be obtained under different presentation conditions, we manipulated the duration of prime presentation. Experiment 1 examined masked priming effects for consonant- or vowel-related primes with 33 ms prime durations, while Experiments 2 and 3 examined masked priming effects with longer prime processing times (66 ms or 50 + 16 ms). Results replicated the relative advantage of consonant over vocalic priming, and established that the consonant bias was not at the orthographic level but rather at the phonological and lexical levels. Furthermore, primes sharing vowels with the target showed inhibition for longer processing times. The implications of these findings for models of visual word recognition are discussed.

Word learning and phonetic processing in preschool-age children

Consonants and vowels have been shown to play different relative roles in different processes, including retrieving known words from pseudowords during adulthood or simultaneously learning two phonetically similar pseudowords during infancy or toddlerhood. The current study explores the extent to which French-speaking 3- to 5-year-olds exhibit a so-called “consonant bias” in a task simulating word acquisition, that is, when learning new words for unfamiliar objects. In Experiment 1, the to-be-learned words differed both by a consonant and a vowel (e.g., /byf/–/duf/), and children needed to choose which of the two objects to associate with a third one whose name differed from both objects by either a consonant or a vowel (e.g., /dyf/). In such a conflict condition, children needed to favor (or neglect) either consonant information or vowel information. The results show that only 3-year-olds preferentially chose the consonant identity, thereby neglecting the vowel change. The older children (and adults) did not exhibit any response bias. In Experiment 2, children needed to pick up one of two objects whose names differed on either consonant information or vowel information. Whereas 3-year-olds performed better with pairs of pseudowords contrasting on consonants, the pattern of asymmetry was reversed in 4-year-olds, and 5-year-olds did not exhibit any significant response bias. Interestingly, girls showed overall better performance and exhibited earlier changes in performance than boys. The changes in consonant/vowel asymmetry in preschoolers are discussed in relation with developments in linguistic (lexical and morphosyntactic) and cognitive processing.