0-36 Aylık Çocuklarda Çalışma Belleği Gelişimi Üzerine Sistematik Bir İnceleme
Bilginin geçici olarak depolanması ve manipüle edilmesine dâhil olan bilişsel süreçler grubunu ifade eden çalışma belleği, insanoğlunun çevre ile aktif olarak etkileşime girdiği, gözlem ve muhakeme yoluyla yeni beceriler kazandığı erken çocukluk döneminde kritik bir öneme sahiptir. Bu nedenle erken çocukluk döneminde çalışma belleği ile ilgili yapılan bilimsel çalışmaların farklı ölçütler açısından incelenmesinin erken müdahale fırsatları yaratmada ve bu alanda çalışmak isteyen araştırmacılara yön verme konusunda yararlı olacağı düşünülmektedir. Bu araştırmanın amacı, 0-36 aylık normal gelişim gösteren çocukların çalışma belleği ile ilgili 2015-2023 yılları arasında yapılan araştırmaların sistematik bir analizini yaparak çalışma belleğini etkileyen çevresel ve bireysel faktörleri belirlemek ve çalışma belleğinin dil gelişimi ile olan ilişkisini incelemektir. Çalışmaya, Mart 2015-Ağustos 2023 tarihleri arasında gerçekleştirilmiş ve tam metinlerine erişilebilen, 0-36 aylık çocukların çalışma belleğini konu alan bilimsel araştırmalar dahil edilmiştir. Veri tabanlarında konu başlığı ve çalışmanın amacıyla ilişkisi düşünülerek belirlenen İngilizce "working memory, infant or toddler or young child" anahtar sözcüğü ve Türkçe "çalışma belleği, bebek veya yeni yürüyen çocuk veya 0-36 aylık" anahtar sözcüğü ile arama yapılmıştır. İngilizce arama sonucunda 536 makale, Türkçe arama sonucunda 41 makale belirlenmiştir. PRISMA protokolü ve PICOS yaklaşımı kullanılarak başlangıçta belirlenen 577 çalışmadan 56’sı çalışmaya dâhil edilmiştir. Araştırmaların analizi sonucunda; yaş ile birlikte çocukların çalışma belleği becerilerinin arttığı ve daha etkili stratejiler geliştirdikleri, dil gelişimi ile çalışma belleğinin ilişkili olduğu görülmüştür. Ayrıca araştırma bulgularına göre, çocukların çalışma belleğini etkileyen bazı çevresel faktörler (ihmal, anne eğitim düzeyi, aile gelir düzeyi, ebeveyn iletişimi vb.) ve bireysel faktörler (dikkat, dopamin seviyesi, cinsiyet vb.) belirlenmiştir. Araştırmalarda 0-36 aylık çocukların çalışma belleği performanslarını ölçmek için farklı yöntem ve teknikler denedikleri görülmüştür. Sonuç olarak; 0-36 ay arası çocuklar üzerinde 2015-2023 yılları arasında yapılan araştırmaların erken müdahale için önemli bulgular sunduğu görülmektedir.
A Systematic Review of Working Memory Development in Children Aged 0-36 Months
Working memory, which refers to the group of cognitive processes involved in the temporary storage and manipulation of information, has a critical importance in early childhood, when human beings actively interact with the environment and acquire new skills through observation and reasoning. For this reason, it is thought that examining scientific studies on working memory in early childhood in terms of different criteria will be useful in creating early intervention opportunities and guiding researchers who want to work in this field. The purpose of this study is to systematically analyze the studies conducted between 2015 and 2023 on the working memory of normally developing children aged 0-36 months to determine the environmental and individual factors affecting working memory and to examine the relationship between working memory and language development. Scientific studies conducted between March 2015 and August 2023 on the working memory of children aged 0-36 months whose full texts were accessible were included in the study. The databases were searched with the keywords "working memory, infant or toddler or young child" in English and "çalışma belleği, “bebek” veya “yeni yürüyen çocuk" in Turkish, which were determined by considering the relationship between the subject title and the purpose of the study. The English search resulted in 536 articles and the Turkish search resulted in 41 articles. Using the PRISMA protocol and the PICOS approach, 56 of the 577 studies initially identified were included in the study. As a result of the analysis of the studies, it was seen that children’s working memory skills increase with age and they develop more effective strategies, and that language development and working memory are mutually related. In addition, according to the research findings, some environmental factors (neglect, maternal education level, family income level, parental communication, etc.) and individual factors (attention, dopamine level, gender, etc.) affecting children's working memory were determined. It has been observed that different methods and techniques have been tried to measure the working memory performance of children aged 0-36 months. In conclusion, it is seen that the studies conducted on children aged 0-36 months between 2015 and 2023 provide important findings for early intervention.
Working memory (WM) can be thought of as a mental notebook that we can use to record useful information for short periods of time when needed in our daily cognitive activities. As defined in Atkinson and Shiffrin’s (1968) model of multiple memory systems, while short-term memory is used more for storage purposes, working memory is a concept that aims to perform operations. Short-term memory controlled by repetition, encoding and search strategies for memorization is used when new information is stored. On the other hand, working memory is used to recall the necessary information from long-term memory and to perform operations on it. Working memory is actually closely related to long-term memory as it works on previously stored information. Working memory refers to the place where information is made sense of and processed (Bruning, 2014).
Working memory plays a crucial role in early childhood (0-3 years), emphasized across various fields such as psychology, neuroscience, child development, education, and even economics (Ozawa et al., 2022; Raver and Blair, 2016;) From birth, infants demonstrate remarkable learning and memory capacities, which are significantly shaped by their interactions with their environment (Cowan, 2007). The development of working memory during the first three years is pivotal, supporting the rapid acquisition of new skills through observation and reasoning (Eangle, 2002). Understanding the progression of working memory over time is essential for designing effective strategies to maximize cognitive capacities and for developing appropriate intervention programs.
Research consistently shows that working memory performance improves significantly with age. For example, Nikolaewa et al. (2021) demonstrated that working memory skills steadily increase from ages 3 to 14, emphasizing the role of early cognitive support in boosting later academic success. Early intervention programs during this period can lay the groundwork for more complex cognitive abilities in later years.
Additionally, working memory is closely linked to other developmental domains, particularly language. Newbury et al. (2016) found strong correlations between early verbal working memory and both receptive and expressive language skills in children aged 2-4, with verbal memory significantly predicting later language development. Similarly, Edmunds et al. (2022) highlighted the relationship between verbal abilities and working memory in children with autism spectrum disorder, where verbal self-talk was found to enhance working memory performance.
The environment also plays a critical role in shaping working memory development. Studies have shown that factors such as maternal education, family income, and parental communication positively influence cognitive development (Demeusy et al., 2018; Horton et al., 2020). Buschmann et al. (2015) highlighted the importance of parent-based language interventions, which improved phonological memory and episodic recall in children. Furthermore, Treat et al. (2019) demonstrated that parents’ adverse childhood experiences negatively impacted their children’s working memory and cognitive flexibility.
In summary, the development of working memory and its interplay with language, environmental influences, and individual differences, such as attention and gender (Hill et al., 2014; Horton, 2020), is crucial for understanding cognitive growth. This body of research also highlights gaps in the literature and provides directions for future research in early childhood development.
There is no systematic analysis in the literature regarding on working memory, especially on the working memory of young children. Such researches will offer an insight to researchers in terms of gaining knowledge about the subject, identifying gaps and needs, and identifying new topics to be researched. It is thought that examining scientific studies on working memory in early childhood in terms of different criteria will be useful in creating early intervention opportunities and guiding researchers who want to work in this field.
Therefore, in this study, it was aimed to conduct a systematic analysis of studies between 2015 and 2023 on the working memory of typically developing children aged 0-36 months. Within the scope of the study, answers were sought to the following questions:
- Do children’s working memory performances vary according to age groups?
- What are the methods and techniques used to measure working memory in infants and toddlers?
- Is there a relationship between working memory development and infants’ language development?
- What are the environmental factors that affect working memory?
- What are the individual differences that affect working memory?
Method
This study conducted a systematic review of studies examining working memory in children aged 0–36 months. The systematic analysis was conducted using the PICOS approach and the basic principles expressed in PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).
The PICOS approach provides a structured framework for conducting systematic reviews and meta-analyses, ensuring clear criteria for study inclusion and improving the validity and reliability of the findings (Higgins et al., 2019). PICOS consists of five key components: Population, Interventions, Comparators, Outcomes, and Study Design. In this study, the population was defined as normally developing children aged 0-36 months, with research focusing on interventions that enhance or measure working memory abilities. Studies without direct relevance to working memory or those involving non-comparable populations were excluded. Comparators include control groups or alternative interventions, allowing for an analysis of the efficacy of various working memory interventions. The outcomes were centered on working memory performance, and only original research designs, such as longitudinal, cross-sectional, and experimental studies, were included, excluding meta-analyses or systematic reviews (Methley et al., 2014; Schardt et al., 2007).
The PRISMA protocol ensures transparency, consistency, and objectivity in systematic reviews and meta-analyses (Moher et al., 2009). It consists of four main stages: Identification, Screening, Eligibility, and Inclusion (Liberati et al., 2009). The identification phase involves a thorough search of databases to identify studies related to working memory in children aged 0-36 months. Between March 2015 and August 2023, databases such as PubMed, EBSCO, and others were searched using keywords like "working memory" and "infant," yielding 577 articles. During the screening phase, duplicate and irrelevant studies were removed. A total of 131 duplicate studies were excluded, leaving 446 articles for further review. The eligibility phase involved reviewing the titles and abstracts to ensure that the studies met the inclusion criteria. Studies were included if they focused on normally developing children aged 0-36 months and examined their working memory abilities. Studies on preterm or atypically developing children or those focusing on other cognitive functions like long-term memory were excluded. After this process, 56 relevant studies remained. In the inclusion phase, the selected studies were analyzed for systematic review. The 56 studies included in the analysis are detailed in the appendix of the research. This process ensured that only relevant, high-quality studies were included in the final review. This structured approach enhances the reliability and reproducibility of the systematic review, ensuring that the findings are comprehensive and valid.
Results
This systematic review aimed to analyze studies focusing on working memory (WM) in children aged 0-36 months, providing insights into age-related changes, environmental and individual factors, and the relationship between WM and language development. The findings enhance the existing literature and open new avenues for research by examining these aspects through the lens of relevant studies.
Age-Related Differences in the Working Memory
The results reveal clear age-related differences in WM performance. For infants aged 0-12 months, studies have shown that they can remember temporal sequences, track auditory cues, and represent objects and their locations (Courage et al., 2006). By 13-24 months, children begin to display more advanced WM skills, such as using perceptual contrasts and retaining numerical information (Simmering \& Perone, 2013). The most complex WM abilities, including multiple identity tracking and symbol-based learning, appear by 25-36 months, which children show an increased ability to encode and sustain memory representations using attentional resources (Baddeley \& Hitch, 1974; Reynolds \& Romano, 2016).
These findings align with the broader cognitive development literature, which underscores the rapid growth of WM during early childhood. Baddeley and Hitch (1974) postulated that WM evolves with age and plays a crucial role in supporting other cognitive functions. Diamond and Doar (1989) further demonstrated that WM and executive functions develop rapidly by age three, significantly improving cognitive performance. Overall, the studies reviewed confirm that children employ more efficient strategies for using WM as they grow, influenced by both maturation and experience.
Environmental Factors Affecting Working Memory
WM development is closely linked to various environmental factors. The analysis highlights the role of maternal education and family income, showing that children from higher socioeconomic backgrounds typically exhibit stronger WM performance (Horton et al., 2020; Wijeakumar et al., 2019). This finding is consistent with broader research linking socioeconomic status (SES) to cognitive outcomes. Studies like Passarelli-Carrazzoni et al. (2018) and Mooney et al. (2021) found similar associations between SES and WM, emphasizing the importance of early interventions for children from low-SES backgrounds.
Parental behaviors, particularly parenting styles and early interactions, significantly shape WM development. Research by Demeusy et al. (2018) and Treat et al. (2019) demonstrated that neglectful or harsh parenting negatively affects children’s WM abilities, while supportive and stimulating interactions promote cognitive growth. This aligns with Bronfenbrenner and Morris’s (2006) ecological systems theory, which emphasizes how child development is shaped by the quality of caregiver-child interactions. Maternal mental health also plays a role, with maternal depression shown to negatively impact children's WM through reduced quality in mother-child interactions (Goodman et al., 2011; Gueron-Sela et al., 2018).
Individual Differences in the Working Memory
Individual factors, such as gender, attention, and neurochemical influences, also impact WM performance in young children. Gender differences in WM were observed in studies like Horton et al. (2020), which found that girls outperformed boys in WM tasks at 18 and 24 months, diverging from some previous findings that favored boys in spatial memory tasks (Harness et al., 2008). However, the developmental trajectory of WM remains a topic of debate, as some studies suggest that gender differences in WM could be shaped by environmental expectations and educational contexts (Hyde et al., 2008).
Attention control, another critical factor, has yielded mixed results in its relationship with WM. Cheng et al. (2019a) found that sustained attention positively influences WM performance, while Holmboe et al. (2018) reported no significant long-term relationship between early attention skills and later WM. Dopamine function, measured through indicators like blink rates, has also been linked to WM performance, further emphasizing the role of neurochemical factors in cognitive development (Bacher et al., 2017; Cools \& D'Esposito, 2011).
Methods for Measuring Working Memory in Infants
The systematic review also highlighted the diverse methods used to assess WM in infants. Techniques such as automated eye-tracking (Chhaya et al., 2018; Ross-Sheehy \& Eschman, 2019) and visual paradigms (Wu et al., 2017) offer precise insights into infants’ cognitive processes but can be technically demanding. Game-based memory tasks like Spin the Pots and Object Retrieval provide more naturalistic settings for evaluating WM (Morra et al., 2021; Zosh \& Feigenson, 2015). Neuroimaging methods such as fNIRS have proven useful in studying early brain development and WM processes, though their use requires stillness from the infants and can be costly (Reyes et al., 2020).
Discussion
This review underscores the importance of WM in early cognitive development, highlighting its age-related progression and the significant role played by environmental and individual factors. Maternal education, socioeconomic status, and parental interaction quality are crucial for optimizing WM development. The findings indicate that children from higher socioeconomic backgrounds and those receiving supportive parenting tend to have stronger WM performance. Individual differences, such as gender and neurochemical influences, also affect WM development, though the extent of these effects remains a subject for further research.
The review also shows that various methods have been used to measure WM in infants, each with its own strengths and weaknesses. Automated eye tracking and neuroimaging methods offer precise insights but are technically challenging, while game-based tasks provide more naturalistic assessments. These various approaches contribute to a more comprehensive understanding of WM development but also highlight the difficulties in standardizing measurement techniques.
Further research is needed to explore under-studied factors such as sleep and screen exposure and to investigate the role of bilingualism and music education on WM in younger children. Expanding research across different cultural contexts is also essential to fully understand WM development in diverse populations. The findings of this review provide a foundation on which future studies can build and highlight the need for targeted interventions that consider both environmental and individual influences on the development of WM.
