Critical Periods in Speech Perception: New Directions

Werker, J. F., & Hensch, T. K. (2015). Critical periods in speech perception: new directions. Annual review of psychology, 66.

This comprehensive review paper discusses the steps that support language development within the context of critical or sensitive periods. Critical or sensitive periods are windows, typically early in development, during which a sensory system is open to restructuring or learning based on input from the environment.

Original views on a critical period for language acquisition proposed that this window closed at the onset of puberty (e.g.: Lennenberg, 1967). However, this view has become much more nuanced, with language acquisition being characterized by multiple critical and sensitive periods throughout early development. The research reviewed in this paper demonstrates that infants become attuned to the properties of language gradually throughout development. This process of development starts with a sensitivity to global properties of language, such as being able to distinguish speech versus non-speech sounds. As infants develop, they become more sensitive to the fine-grained details in their native language. These processes are defined by critical periods, and development within these critical periods relies on both biological and environmental factors.

Some of the strongest evidence for critical periods in language acquisition comes from work examining phoneme discrimination in young infants. Phonemes are the units of sound in a language, such as the sounds /k/, /æ/, and /t/ in the word “cat”. Young infants are capable of discriminating phonemes from across the world’s languages. However, there is a process of perceptual narrowing around 8 to 10 months of age, which sharpens their perception to only those phoneme distinctions that are used in their native language. For example, an infant reared in an Japanese-speaking environment could discriminate between the phonemes /r/ and /l/ at 6 but not 10 months of age. This is because the phonetic distinction between these phonemes is not present in the Japanese language. However, an infant reared in an English-speaking environment can continue to discriminate between these phonemes after 10 months of age because the phonetic distinction between /r/ and /l/ is present in the English language. Once phoneme categories are in place at around 10 months of age, infants begin to show sensitivity to more complex aspects of language, such as recognizing familiar words in their native language. This example highlights how native language experience shapes perception, and the gradual and sequential native of language development.

Critical periods can be impacted by both biological and environmental factors. For instance, exposure to pharmacological agents during pregnancy can affect language critical periods. Additionally, factors such as being raised in a bilingual environment or receiving a cochlear implant can alter critical periods. Critical periods are important to understand because they demonstrate how early language exposure shapes later language skills. Overall, by examining language critical periods, clinicians and researchers can broaden their understanding of how language development unfolds.

Blogger: Nicolette Noonan is a PhD Candidate in Psychology, supervised by Dr. Lisa Archibald and Dr. Marc Joanisse

Applying an Integrative Framework of Executive Function to Preschoolers with Specific Language Impairment

Kapa, L. L., Plante, E. & Doubleday, K.(2017). Applying an Integrative Framework of Executive Function to Preschoolerswith Specific Language Impairment. Journalof Speech, Language, and Hearing Research. 60(8). 1-15.

Executive functions refer to those cognitive processes needed to concentrate and pay attention. Core executive functions include inhibition, working memory, and cognitive flexibility. Inhibition refers to the ability to stop paying attention to distractions. Working memory involves the holding and manipulation of information in memory. Cognitive flexibility (or switching) is the ability to flexibly shift between tasks and stimuli, and involves the coordination of multiple executive functions. These abilities support the ability to focus and sustain attention. All of these components are considered interrelated, but separable. Executive functions are important in complex, goal-driven tasks such as school learning.

Executive functions are associated with language learning. Consistent with this notion are findings that children with Developmental Language Disorder (DLD), also known as Specific Language Impairment (SLI), score poorly on some measures of executive functions. Nevertheless, poor scores on executive functions in children with DLD could be due to their poor verbal skills, as many executive functions tasks tap verbal ability. This study addressed this issue by comparing performance of preschool children with DLD on verbal and nonverbal measures of executive functions. A second purpose of the study was to examine a possible hierarchical relationship amongst executive functions with sustained attention underlying working and inhibition, both of which support shifting.

In this study, 26 4- and 5-year-olds diagnosed with DLD and 26 typically developing age-and sex-matched peers completed verbal and nonverbal measures of the following four specific executive function components: sustained selective attention, working memory, inhibition, and shifting. Lower scores for the DLD than typical group were observed on both verbal and nonverbal measures of sustained selective attention and working memory, the verbal inhibition task, and the nonverbal shifting task. These results provided evidence for executive function deficits in preschoolers that are not limited to the verbal domain. A linear relationship was noted however not in the order expected with largest group differences observed for the sustained attention tasks, and smallest for working memory.

Findings of executive function deficits in children with DLD continue to point to the need to investigate impacts for assessment and intervention.

Blogger: Ren Lohmann is an MA student in Linguistics, supervised by Dr. Lisa Archibald.

Why do early mathematics skills predict later reading? The role of mathematical language

Purpura, D.J., Logan, J.A.R.,Hassinger-Das, B., & Napoli, A.R. (2017). Why do early mathematics skillspredict later reading? The role of mathematical language.

Reading and math tasks both depend on oral language and code-related skills. Math and literacy share a persistent bidirectional developmental relationship. Considerable evidence has demonstrated that early reading predicts later math, but the opposite relationship has also been reported. In the case of early math predicting later reading skills, the extent to which this relationship can be accounted for simply by the language load of early math tasks or reflects a unique association is unclear. The present study examined whether the relationship between early math and later reading skills is mediated by mathematical language ability.

A total of 136 preschool children completed measures of early numeracy skills and mathematical language, early literacy skills (print knowledge, phonological awareness, definitional vocabulary), and general cognitive ability at the beginning of the school year, and again about 5 months later. The mathematical language measure assessed comparative language (e.g., combine, more) and spatial language (e.g., near, far). In multilevel modelling, the relationship between early numeracy skills and later reading was entirely mediated by mathematical language ability.

Although this study examines predictive relationships over only a 5-month window, it does underscore the language load of early mathematical tasks. The findings highlight the cross curricular impact of language disorders.

Blogger: Lisa Archibald