Staff Profiles

Modules taught

Undergraduate

• PSYC4014 - Contemporary Issues in Psychology
• PSYC4010 - Introduction to Key areas of Psychology
• PSYC4011 - Academic Skills for Psychology
• PSYC5004 - Biological Psychology
• PSYC5007 - Developmental Psychology
• PSYC6007 - Topics in Developmental Psychology
• PSYC6011 - Project

Postgraduate

• PSYC7001 - Brain and Cognition
• PSYC7006 - Intelligence, Personality and Individual Differences
• PSYC7007 - Research Dissertation
• PSYC7008 - Cognitive and Social Aspects of Development

Research grants and awards

2020-2021 The effects of social distancing policies on children’s language development, sleep and executive functions. UKRI and ESRC, £267,166.48 UK.PSYC4014 Contemporary issues:

2015-2019 Early Career Fellowship, The Leverhulme Trust, £216,092 UK.

Research projects

Examples of Research Projects:

• The effects of social distancing policies on children’s language development, sleep and executive functions, in collaboration with University of Oxford, University of Leeds, Warwick University and University of East Anglia.
• Early language acquisition in preterm infants and infants from lower-SES families.

• Linking early phonological development and lexical acquisition. Oxford Brookes University (UK) in collaboration with National Autonomous University of Mexico (Mexico).

• Creation of an inventory of phonemic and syllabic frequencies in Spanish. UNAM, Mexico.

•  

  Acquisition of subject-verb agreement forms: Evidence from Spanish-learning children. Johns Hopkins University (USA) in collaboration with LPP- Paris V University (France).

• Learning of non-adjacent phonological dependencies. Laboratoire Psychologie de la Perception (LPP) Paris V University (France), in collaboration with RIKEN Institute (Japan).

• Comprehension of infrequent subject-verb agreement forms: Evidence from French-learning children. LPP- Paris V University (France) in collaboration with Johns Hopkins University (USA).

• Learning of non-adjacent vocalic dependencies. LPP- Paris V University (France) in collaboration with the Central European University (Hungary).

Further information

Oxford Brookes BabyLab

Journal articles

• Gonzalez-Gomez N, O’Brien F, Harris M, 'The effects of Prematurity and Socioeconomic deprivation on early Phonological Development: A Story of Two Different Delays'
  Developmental Science x (2020)
  ISSN: 1363-755X
  Abstract

  There is evidence showing that both maturational and environmental factors can impact on later language development. On the one hand, preterm birth has been found to increase the risk of deficits in the preschool and school years. Preterm children show poorer auditory discrimination, reading difficulties, poor vocabulary, less complex expressive language and lower receptive understanding than their matched controls. On the other hand, socioeconomic status indicators (i.e. income, education, occupation) have been found to be strongly related to linguistic abilities during the preschool and school years. However, there is very little information about how these factors result in lower linguistic abilities. The present study addresses this issue. To do so, we investigated early phonological development in full and preterm infants from families classed as high or low SES. 76 infants were followed longitudinally at 7.5, 9, 10.5 and 12 months of age. At each test point, three studies explored infants’ phonetic, prosodic and phonotactic development, respectively. Results showed no significant differences between the phonetic or the phonotactic development of the preterm and the full-term infants. However, a time-lag between preterm and full-term developmental timing for prosody was found. Socioeconomic status did not have a significant effect on prosodic development. Nonetheless, phonetic and phonotactic development were affected by SES, infants from lower SES showed phonetic discrimination of non-native contrast and a preference for high-frequency sequences later than their more advantaged peers. Overall these results suggest that different constraints apply to the acquisition of different phonological subcomponents.
  

  Website 
• The ManyBabies Consortium, 'Quantifying sources of variability in infancy research using the infant-directed speech preference'
  Advances in Methods and Practices in Psychological Science 3 (1) (2020) pp.24-52
  ISSN: 2515-2459
  Abstract

  The field of psychology has become increasingly concerned with issues related to methodology and replicability. Infancy researchers face specific challenges related to replicability: high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations, amongst other factors. Addressing these concerns, we report on a large-scale, multi-site study aimed at 1) assessing the overall replicability of a single theoretically-important phenomenon and 2) examining methodological, situational, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult were created using semi-naturalistic laboratory-based audio recordings in North American English. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three commonly-used infant discrimination methods (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s *d*) was 0.35 [0.29 - 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together these findings replicate the infant-directed speech preference but suggest that its magnitude is modulated by development, native language experience, and testing procedure.
  

  Website 
• Byers-Heinlein K, Barr R, Black A, Brown A, Durrant S, Gampe A, Gonzalez-Gomez N, Hay JF, Hernik M, Jartó M, Kovács AM, Laoun-Rubenstein A, Lew-Williams C, Liszkowski U, Liu L, Noble C, Potter CE, Rocha-Hidalgo J, Sebastian-Galles N, Soderstrom M, Ka-Ying Tsui R, an Renswoude D, Visser I, Waddell C, Wermelinger S, & Singh L, 'The Development of Gaze Following in Monolingual and Bilingual Infants: A Multi-Lab Study'
  Infancy x (2020)
  ISSN: 1525-0008 eISSN: 1532-7078
  Abstract

  Determining the meanings of words requires language learners to attend to what other
  people say. However, it behooves a young language learner to simultaneously attend to what
  other people attend to, for example, by following the direction of their eye gaze. Sensitivity to
  cues such as eye gaze might be particularly important for bilingual infants, as they encounter less
  consistency between words and objects than monolinguals, and do not always have access to the
  same word learning heuristics (e.g., mutual exclusivity). In a pre-registered study, we tested the
  hypothesis that bilingual experience would lead to a more pronounced ability to follow another’s
  gaze. We used the gaze-following paradigm developed by Senju and Csibra (2008) to test a total
  of 93 6–9 month-old and 229 12–15 month-old monolingual and bilingual infants, in 11 labs
  located in 8 countries. Monolingual and bilingual infants showed similar gaze-following abilities,
  and both groups showed age-related improvements in speed, accuracy, frequency and duration of
  fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations
  to onscreen objects, whether or not they were cued by the actor. These results suggest that gaze
  sensitivity is a fundamental aspect of development that is robust to variation in language
  exposure.
  

• Gonzalez-Gomez N, Schmandt S, Fazekas J, Nazzi, T, Gervain J, 'Infants’ sensitivity to nonadjacent vowel dependencies: The case of vowel harmony in Hungarian'
  Journal of Experimental Child Psychology 178 (2018) pp.170-183
  ISSN: 0022-0965 eISSN: 1096-0457
  Abstract

  Vowel harmony is a linguistic phenomenon whereby vowels within a word share one or several of their phonological features, constituting a nonadjacent, and thus challenging, dependency to learn. It can be found in a large number of agglutinating languages, such as Hungarian and Turkish, and it may apply both at the lexical level (i.e., within word stems) and at the morphological level (i.e., between stems and their affixes). Thus, it might affect both lexical and morphological development in infants whose native language has vowel harmony. The current study asked at what age infants learning an irregular harmonic language, Hungarian, become sensitive to vowel harmony within word stems. In a head-turn preference study, 13-month-old, but not 10-month-old, Hungarian-learning infants preferred listening to nonharmonic VCV (vowel–consonant–vowel) pseudowords over vowel-harmonic ones. A control experiment with 13-month-olds exposed to French, a nonharmonic language, showed no listening preference for either of the sequences, suggesting that this finding cannot be explained by a universal preference for nonharmonic sequences but rather reflects language-specific knowledge emerging between 10 and 13 months of age. We discuss the implications of this finding for morphological and lexical learning.
  

  Website 
• Gonzalez-Gomez N, Hsin L, Barrière I, Nazzi T, Legendre G, 'Agarra, agarran: Evidence of Early Comprehension of Subject-Verb Agreement in Spanish'
  Journal of Experimental Child Psychology 160 (2017) pp.33-49
  ISSN: 0022-0965 eISSN: 1096-0457
  Abstract Studies across many languages (e.g., Dutch, English, Farsi, Spanish, Xhosa) have failed to show early acquisition of subject-verb agreement, while recent studies on French reveal acquisition by 30 months of age. Using a similar procedure as in previous French studies, the present study evaluated whether earlier comprehension of subject-verb agreement in (Mexican) Spanish can be revealed when task demands are lowered. Two experiments using a touch-screen pointing task tested comprehension of SV agreement by monolingual Spanish-speaking children growing up in Mexico City, between about 3 and 5 years of age. In Experiment 1, the auditory stimuli consisted of a transitive verb+pseudonoun object (e.g. agarra el micho ‘he throws the micho’ vs. agarran el duco ‘they throw the duco’); results failed to show early comprehension of SV agreement, replicating previous findings. In Experiment 2, the same stimuli were used, with the crucial difference that the word objeto ‘object’ replaced all pseudonouns; results revealed SV agreement comprehension as early as 41 to 50 months. Taken together, our findings show that comprehension at this age is facilitated when task demands are lowered, here by not requiring children to process pseudowords (even when these were not critical to the task). These findings hence underscore the importance of task-/stimulus-specific features when testing early morphosyntactic development, and suggest that previous results may have underestimated Spanish-speaking children’s competence.Website 
• Gonzalez-Gomez N, Nazzi T, 'Delayed acquisition of non-adjacent vocalic dependencies'
  Journal of Child Language 43 (1) (2016) pp.186-206
  ISSN: 0305-0009
  Abstract

  The ability to compute non-adjacent regularities is key in the acquisition of a new language. In the domain of phonology/phonotactics, sensitivity to non-adjacent regularities between consonants has been found to appear between 7 and 10 months. The present study focuses on the emergence of a posterior-anterior (PA) bias, a regularity involving two non-adjacent vowels. Experiments 1 and 2 show that a preference for PA over AP (anterior-posterior) words emerges between 10 and 13 months in French-learning infants. Control experiments show that this bias cannot be explained by adjacent or positional preferences. The present study demonstrates that infants become sensitive to non-adjacent vocalic distributional regularities between 10 and 13 months, showing the existence of a delay for the acquisition of non-adjacent vocalic regularities compared to equivalent non-adjacent consonantal regularities. These results are consistent with the CV hypothesis, according to which consonants and vowels play different roles at different linguistic levels.

  Website 
• Culbertson J, Koulaguina E, Gonzalez-Gomez N, Legendre G, Nazzi T, 'Developing Knowledge of Nonadjacent Dependencies'
  Developmental Psychology 52 (12) (2016) pp.2174-2183
  ISSN: 0012-1649
  Abstract Characterizing the nature of linguistic representations and how they emerge during early development is a central goal in the cognitive science of language. One area in which this development plays out is in the acquisition of dependencies—relationships between co-occurring elements in a word, phrase, or sentence. These dependencies often involve multiple levels of representation and abstraction, built up as infants gain experience with their native language. The authors used the Headturn Preference Procedure to systematically investigate the early acquisition of 1 such dependency, the agreement between a subject and verb in French, at 6 different ages between 14 and 24 months. The results reveal a complex developmental trajectory that provides the first evidence that infants might indeed progress through distinct stages in the acquisition of this nonadjacent dependency. The authors discuss how changes in general cognition and representational knowledge (from reflecting surface statistics to higher-level morphological features) might account for their findings. These findings highlight the importance of studying language acquisition at close time intervals over a substantial age range.Website 
• Nazzi T, Nishibayashi LL, Berdasco-Munoz E, Baud O, Biran V, Gonzalez-Gomez N, 'Language acquisition in preterm infants during the first year of life'
  ARCHIVES DE PEDIATRIE 22 (10) (2015) pp.1072-1077
  ISSN: 0929-693X
  Abstract Previous studies have shown that preterm children are at a higher risk for cognitive and language delays than full-term children. Most of these studies have concentrated on the effects of prematurity during the preschool or school years, while the effect of preterm birth on the early development of language, much of which occurs during the first year of life, remains very little explored. This article focuses on this crucial period and reviews the studies that have explored early phonological and lexical development in preterm infants. The results of these studies show uneven proficiency in different language subdomains in preterm infants. This raises the possibility that different constraints apply to the acquisition of different linguistic subcomponents in this population, in part as a result of a complex interaction between maturation, experience, and language subdomains. (C) 2015 Elsevier Masson SAS. All rights reserved.Website 
• Gonzalez-Gomez N, Hayashi A, Tsuji S, Mazuka R, Nazzi T, 'The role of the input on the development of the LC bias: A crosslinguistic comparison'
  Cognition 132 (3) (2014) pp.301-311
  ISSN: 0010-0277
  Abstract
  Previous studies have described the existence of a phonotactic bias called the Labial–Coronal
  (LC) bias, corresponding to a tendency to produce more words beginning with a labial
  consonant followed by a coronal consonant (i.e. ‘‘bat’’) than the opposite CL pattern (i.e.
  ‘‘tap’’). This bias has initially been interpreted in terms of articulatory constraints of the
  human speech production system. However, more recently, it has been suggested that this
  presumably language-general LC bias in production might be accompanied by LC and CL
  biases in perception, acquired in infancy on the basis of the properties of the linguistic
  input. The present study investigates the origins of these perceptual biases, testing infants
  learning Japanese, a language that has been claimed to possess more CL than LC sequences,
  and comparing them with infants learning French, a language showing a clear LC bias in its
  lexicon. First, a corpus analysis of Japanese IDS and ADS revealed the existence of an overall
  LC bias, except for plosive sequences in ADS, which show a CL bias across counts. Second,
  speech preference experiments showed a perceptual preference for CL over LC plosive
  sequences (all recorded by a Japanese speaker) in 13- but not in 7- and 10-month-old
  Japanese-learning infants (Experiment 1), while revealing the emergence of an LC preference
  between 7 and 10 months in French-learning infants, using the exact same stimuli.
  These crosslinguistic behavioral differences, obtained with the same stimuli, thus reflect
  differences in processing in two populations of infants, which can be linked to differences
  in the properties of the lexicons of their respective native languages. These findings establish
  that the emergence of a CL/LC bias is related to exposure to a linguistic input.
  Website 
• Gonzalez-Gomez N,Nazzi T, 'Constraints on statistical computations at 10 months of age: the use of phonological features.'
  Developmental Science 18 (6) (2014) pp.864-876
  ISSN: 1363-755X
  Abstract

  Recently, several studies have argued that infants capitalize on the statistical properties of natural languages to acquire the linguistic structure of their native language, but the kinds of constraints which apply to statistical computations remain largely unknown. Here we explored French-learning infants' perceptual preference for labial-coronal (LC) words over coronal-labial words (CL) words (e.g. preferring bat over tab) to determine whether this phonotactic preference is based on the acquisition of the statistical properties of the input based on a single phonological feature (i.e. place of articulation), multiple features (i.e. place and manner of articulation), or individual consonant pairs. Results from four experiments revealed that infants had a labial-coronal bias for nasal sequences (Experiment 1) and for all plosive sequences (Experiments 2 and 4) but a coronal-labial bias for all fricative sequences (Experiments 3 and 4), independently of the frequencies of individual consonant pairs. These results establish for the first time that constellations of multiple phonological features, defining broad consonant classes, constrain the early acquisition of phonotactic regularities of the native language.

  Website 
• Gonzalez-Gomez N, Nazzi T, 'Effects of Prior Phonotactic Knowledge on Infant Word Segmentation: The Case of Nonadjacent Dependencies'
  JOURNAL OF SPEECH LANGUAGE AND HEARING RESEARCH 56 (2013) pp.840-849
  ISSN: 1092-4388
  Abstract
  Purpose In this study, the authors explored whether French-learning infants use nonadjacent phonotactic regularities in their native language, which they learn between the ages of 7 and 10 months, to segment words from fluent speech.
   
  Method Two groups of 20 French-learning infants were tested using the head-turn preference procedure at 10 and 13 months of age. In Experiment 1, infants were familiarized with 2 passages: 1 containing a target word with a frequent nonadjacent phonotactic structure and the other containing a target word with an infrequent nonadjacent phonotactic structure in French. During the test phase, infants were presented with 4 word lists: 2 containing the target words presented during familiarization and 2 other control words with the same phonotactic structure. In Experiment 2, the authors retested infants' ability to segment words with the infrequent phonotactic structure.
   
  Results Ten- and 13-month-olds were able to segment words with the frequent phonotactic structure, but it is only by 13 months, and only under the circumstances of Experiment 2, that infants could segment words with the infrequent phonotactic structure.
   
  Conclusion These results provide new evidence showing that infant word segmentation is influenced by prior nonadjacent phonotactic knowledge.
  Website 
• Gonzalez-Gomez N, Poltrock S, Nazzi T, 'A “Bat” Is Easier to Learn than a “Tab”: Effects of Relative Phonotactic Frequency on Infant Word Learning'
  PLoS ONE 8 (3) (2013) pp.e59601-
  ISSN: 1932-6203
  Website 
• Gonzalez-Gomez N, Nazzi T, 'Effects of prior phonotactic knowledge on infant word segmentation: the case of non-adjacent dependencies'
  Journal of Speech, Language, and Hearing Research 56 (2013) pp.840-849
  ISSN: 1092-4388
  Abstract
  Purpose: In the present study, we explore whether French-learning infants use non-adjacent
  phonotactic regularities in their native language, which they learn between 7 and 10 months of
  age, to segment words from fluent speech.
  Method: Two groups of 20 French-learning infants were tested using the head-turn
  preference procedure at 10 and 13 months of age. In Experiment 1, infants were familiarized
  with two passages: one containing a target word with a frequent non-adjacent phonotactic
  structure and the other passage containing a target word with an infrequent non-adjacent
  phonotactic structure in French. During the test phase infants were presented with 4 word
  lists: two containing the target words presented during familiarization and two other control
  words with the same phonotactic structure. In Experiment 2, we retested infants’ ability to
  segment words with the infrequent phonotactic structure.
  Results: Ten- and 13-month-olds were able to segment words with the frequent phonotactic
  structure, but it is only by 13 months, and only under the circumstances of Experiment 2, that
  infants could segment words with the infrequent phonotactic structure.
  Conclusions: Our results provide new evidence showing that infant word segmentation is
  influenced by prior non-adjacent phonotactic knowledge.
  Website 
• Tsuji S, Gonzalez Gomez N, Medina V, Nazzi T, Mazuka R, 'The labial-coronal effect revisited: Japanese adults say pata, but hear tapa.'
  Cognition 125 (3) (2012) pp.413-428
  ISSN: 0010-0277
  Abstract

  The labial–coronal effect has originally been described as a bias to initiate a word with a labial consonant–vowel–coronal consonant (LC) sequence. This bias has been explained with constraints on the human speech production system, and its perceptual correlates have motivated the suggestion of a perception–production link. However, previous studies exclusively considered languages in which LC sequences are globally more frequent than their counterpart. The current study examined the LC bias in speakers of Japanese, a language that has been claimed to possess more CL than LC sequences. We first conducted an analysis of Japanese corpora that qualified this claim, and identified a subgroup of consonants (plosives) exhibiting a CL bias. Second, focusing on this subgroup of consonants, we found diverging results for production and perception such that Japanese speakers exhibited an articulatory LC bias, but a perceptual CL bias. The CL perceptual bias, however, was modulated by language of presentation, and was only present for stimuli recorded by a Japanese, but not a French, speaker. A further experiment with native speakers of French showed the opposite effect, with an LC bias for French stimuli only. Overall, we find support for a universal, articulatory motivated LC bias in production, supporting a motor explanation of the LC effect, while perceptual biases are influenced by distributional frequencies of the native language.

  Website 
• Gonzalez-Gomez N, Nazzi T, 'Phonotactic acquisition in healthy preterm infants'
  Developmental Science 15 (6) (2012) pp.885-
  ISSN: 1363-755X
  Abstract

  Previous work has shown that preterm infants are at higher risk for cognitive/language delays than full-term infants. Recent studies, focusing on prosody (i.e. rhythm, intonation), have suggested that prosodic perception development in preterms is indexed by maturational rather than postnatal/listening age. However, because prosody is heard in-utero, and preterms thus lose significant amounts of prenatal prosodic experience, both their maturation level and their prosodic experience (listening age) are shorter than that of full-terms for the same postnatal age. This confound does not apply to the acquisition of phonetics/phonotactics (i.e. identity and order of consonants/vowels), given that consonant differences in particular are only perceived after birth, which could lead to a different developmental pattern. Accordingly, we explore the possibility that consonant-based phonotactic perception develops according to listening age. Healthy French-learning full-term and preterm infants were tested on the perception of consonant sequences in a behavioral paradigm. The pattern of development for full-term infants revealed that 7-month-olds look equally at labial-coronal (i.e. /pat/) compared to coronal-labial sequences (i.e. /tap/), but that 10-month-olds prefer the labial-coronal sequences that are more frequent in the French lexicon. Preterm 10-month-olds (having 10 months of phonetic listening experience but 7 months of maturational age) behaved as full-term 10-month-olds. These results establish that preterm developmental timing for consonant-based phonotactic acquisition is based on listening age (experience with input). This questions the interpretation of previous results on prosodic acquisition in terms of maturational constraints, and raises the possibility that different constraints apply to the acquisition of different phonological subcomponents.

  Website 
• Gonzalez-Gomez N, Nazzi T, 'Acquisition of nonadjacent phonological dependencies in the native language during the first year of life'
  Infancy 17 (5) (2012) pp.498-524
  ISSN: 1525-0008
  Abstract
  Languages instantiate many different kinds of dependencies, some holding between adjacent elements and others holding between nonadjacent elements. In the domain of phonology–phonotactics, sensitivity to adjacent dependencies has been found to appear between 6 and 10 months. However, no study has directly established the emergence of sensitivity to nonadjacent phonological dependencies in the native language. The present study focuses on the emergence of a perceptual Labial-Coronal (LC) bias, a dependency involving two nonadjacent consonants. First, Experiment 1 shows that a preference for monosyllabic consonant-vowel-consonant LC words over CL (Coronal- Labial) words emerges between 7 and 10 months in French-learning infants. Second, two experiments, presenting only the first or last two phonemes of the original stimuli, establish that the LC bias at 10 months cannot be explained by adjacent dependencies or by a preference for more frequent coronal consonants (Experiment 2a & b). At 7 months, by contrast, infants appear to react to the higher frequency of coronal consonants (Experiment 3a & b). The present study thus demonstrates that infants become sensitive to nonadjacent phonological dependencies between 7 and 10 months. It further establishes a
  change between these two ages from sensitivity to local properties to nonadjacent dependencies in the phonological domain.
  Website 

Book chapters

• Gonzalez-Gomez N, 'Phonology' in Stephen Hupp and Jeremy Jewell (ed.), The Encyclopedia of Child and Adolescent Development, Wiley (2019)
  ISBN: 9781119161899 eISBN: 9781119171492
  Abstract

  From birth infants have to deal with a huge amount of information in order to learn the properties of their native language. Among other skills, infants have to identify the relevant sounds of their language to form a repertoire (phonetics), the suprasegmental properties accompanying those sounds (prosody) and the rules applying to those sounds (phonotactics); for example, which sounds can be combined and which ones cannot. All of these abilities are part of infants’ early phonological development taking place during the first months of life. A great amount of research has focused on these early acquisitions, and has shown that infants already possess a set of initial capacities to process speech at birth. It is during their first year of life that these initial capacities start changing, leading to a decrease in infants’ ability to discriminate non-native contrasts and an increase in their ability to distinguish native contrasts, a process known as perceptual attunement.
  

  Website 
• Gonzalez-Gomez N, 'Speech Development' in Stephen Hupp and Jeremy Jewell (ed.), Encyclopedia of Child and Adolescent Development, Wiley (2019)
  ISBN: 9781119161899 eISBN: 9781119171492
  Abstract

  Early on infants start vocalising, at first, without meaning but quickly they will start producing sounds to communicate. The first sounds will mainly be composed by vowels, then consonant-vowel sequences (i.e., canonical babbling), followed by repeated syllable sequences (i.e., reduplicated babbling) and later on, infants will produce sequences having two different consonants such as “pata” (i.e., variegated babbling). In parallel, infants have to discover what is and what is not a word-like unit, a process called word segmentation. This is a particularly challenging process given that spoken language is, for most parts, a continuous speech stream. Furthermore, infants also have to associate those word-like units with meaning representations, a process known as word-learning. There is evidence showing that infants are able to understand some words as early as 5 months of age, although infants usually produce their first word around their first birthday.
  

  Website 
• Gonzalez-Gomez N, 'Speech Development' in Stephen Hupp and Jeremy Jewell (ed.), Encyclopedia of Child and Adolescent Development, Wiley (2019)
  ISBN: 9781119161899 eISBN: 9781119171492
  Abstract

  Early on infants start vocalising, at first, without meaning but quickly they will start producing sounds to communicate. The first sounds will mainly be composed by vowels, then consonant-vowel sequences (i.e., canonical babbling), followed by repeated syllable sequences (i.e., reduplicated babbling) and later on, infants will produce sequences having two different consonants such as “pata” (i.e., variegated babbling). In parallel, infants have to discover what is and what is not a word-like unit, a process called word segmentation. This is a particularly challenging process given that spoken language is, for most parts, a continuous speech stream. Furthermore, infants also have to associate those word-like units with meaning representations, a process known as word-learning. There is evidence showing that infants are able to understand some words as early as 5 months of age, although infants usually produce their first word around their first birthday.
  

  Website 

Other publications

• Gonzalez-Gomez N, Nazzi T, 'Phonological Feature Constraints on the Acquisition of Phonological Dependencies'
  PROCEEDINGS OF THE 36TH ANNUAL BOSTON UNIVERSITY CONFERENCE ON LANGUAGE DEVELOPMENT, VOLS 1 AND 2 (2012) pp.202-212ISSN: 1080-692X