In the last decades, scientists have made significant progress in understanding language-music interactions using an array of neurocognitive and genetic approaches. Despite the tacit assumption in this work that the environment affects the structure of neural substrates and the expression of genes, details of early language-music input have been comparatively understudied. The developmental-ecological approach to investigating the dynamics of early language-music input is an important complement to neurocognitive and genetic approaches that can make headway on some of the challenges language-music research has faced.

The developmental-ecological approach (Bronfenbrenner, 1979; West and King, 1987; Adolph, 2019) builds on the view that an adult’s brain and behavior is the product of interactions between the environment and biology throughout development. From this perspective, how we interact with our environment over time is what creates adult cognition, and so we must understand the conditions under which cognitive structures develop, from as early as possible, in as much detail as possible. Because this approach is rooted in the fact that development happens minute-to-minute, day-to-day, in a particular environment, it often involves the capture and description of continuous multi-modal recordings of infants’ daily life. Inherent to this approach is the acknowledgement that inter- and intra-cultural differences can have strong influences on developmental trajectories. For example, the developmental-ecological approach underlies Adolph’s work on motor development (Adolph et al., 2018), which pivoted the field away from describing motor behavior as the logical end of universal constraints and milestones, and toward an integrated perspective that can explain how different factors, from babywearing customs to nutrition, interact with the changing body across the lifespan. Like motor behavior, the processing of language and music should be seen as the result of culturally-dependent experiences that are constrained by social and physical affordances.

In this paper, we describe how understanding the biological and functional relation between language and music requires this developmental-ecological approach. First, we review the limitations of non-ecological approaches to studying language-music development. Then, we explain how a developmental-ecological perspective can address challenges inherent to neurocognitive and genetic approaches to language-music processing. Last, we make recommendations for conducting naturalistic research on early language-music input from a developmental-ecological perspective.

There is evidence within both music and language research that early experience affects later processing and behavior. Children’s early music environment, measured via parent report, is correlated with musical processing and musical success (Brand, 1986; Putkinen et al., 2013; Williams et al., 2015), and the quality and quantity of language exposure affects language processing (Grüter et al., 2014). Researchers have also investigated the interaction of music and language across development. Much of this work uses measures of experience or ability, such as years of music training or productive vocabulary at a certain age, to predict later brain activity and behavior. For example, some training studies have found that listening and learning how to play a musical instrument changes brain and behavioral responses to not only music stimuli, but language tasks as well (see Gordon et al., 2015, for review). Thus, early input, broadly defined, has been shown to affect how we respond to music and language, with some evidence of transfer across domains. This body of evidence has motivated domain-general, learning-based explanations for shared language-music processing (e.g., statistical learning theories such as Schön et al., 2008; Thiessen and Saffran, 2009, and Politimou et al., 2021; stimuli complexity theories such as Lebedeva and Kuhl, 2010; and familiarity-based theories such as Plantinga and Trehub, 2014).

However, the studies above treat early music and language experience as static, monolithic variables rather than continuous, complex streams that change across time. Asking a parent whether they have musical instruments at home (as some surveys do) is informative, but it ignores that the effect of instruments at home depends on the hour-to-hour and minute-to-minute dynamics of how infants interact with those instruments, and how that interaction in turn affects future neural activity and behavior. In order to understand the role of development and the environment in shared language-music processing, researchers need to move beyond summary measures of the environment and embrace the complex dynamics of how music and language input unfold over time.

The developmental-ecological approach argues that to understand the interaction between language and music processing in adults, researchers must not only study children’s musical and language abilities in lab tasks, but also observe how children use the input to adapt to their environment in real-time. Thus, developmental-ecological studies: (1) record from naturalistic settings because adults and children interact differently in structured tasks vs. their daily routines (Tamis-LeMonda et al., 2017); (2) sample across many families, both intra- and interculturally, because childrens’ environments are inherently idiosyncratic and culture-dependent (Casillas et al., 2020; Montag, 2020); and (3) sample frequently and longitudinally because input interacts with development, such that what children see, hear, and touch differs from moment-to-moment and month-to-month (Kretch et al., 2014).

By describing how children engage with music and language across development—in the functional, social, and emotional context of their daily lives—we can develop models that predict language/music processing and production from actual measurements of the variability in early experiences and trajectories. This empirically-grounded approach differs from current models that often make assumptions about universal or cultural biases and experiences that unify or differentiate language and music. For example, studies on musical pitch structure often predict participant responses based on stimulus profiles summarized from musical corpora (e.g., Billboard Top 100, Bach Chorales), which serve as a proxy for musical experience (see for example the use of rock and classical corpora in Vuvan and Hughes, 2021). Developmental-ecological studies of the early music environment would allow researchers to discard such proxies and make predictions based on actual listener experience.

Some areas of language learning research have productively embraced the developmental-ecological approach. For example, in the 1970s, Brown (1973) used a combination of diary studies and tape recordings to describe early syntax and semantic development. The CHILDES database (MacWhinney and Snow, 1990) is a corpus of transcribed and tagged speech to children in both lab and naturalistic settings that has been used to create models of child language learning (e.g., Mintz, 2003). More recently, there has been a renewed interest in collecting day-long, longitudinal audiovisual recordings to describe the nuances of language input in first years of life (e.g., Roy et al., 2015; Tamis-LeMonda et al., 2019; Bulgarelli and Bergelson, 2020; Casillas et al., 2020; Sullivan et al., 2021). This work has led to novel findings, such as the role of context (Roy et al., 2015) and temporal structure (Casillas et al., 2020) in language development.

In contrast, scientific efforts to understand the early music environment largely do not stem from a developmental-ecological perspective, in part because this work has approached music input as an extracurricular, optional enrichment activity (e.g., Schellenberg, 2005). Researchers rarely record music in the daily lives of babies, but instead assess beliefs about and frequency of music engagement through surveys (Brand, 1985, 1986; Dai and Schader, 2002; Custodero et al., 2003; Custodero and Johnson-Green, 2008; de Vries, 2009; Valerio et al., 2012; Mehr, 2014; Williams et al., 2015; Politimou et al., 2021; Steinberg et al., 2021), individual and group interviews (Custodero, 2006; Young, 2008; Barrett, 2009, 2011; de Vries, 2009; Cho, 2015), and diary studies (Custodero, 2006; Barrett, 2009, 2011).

In the last two decades, some music researchers have begun to take an interest in direct observational research of the musical environment, through live observations (Barrett, 2009, 2011), lab recordings (Falk and Kello, 2017), and field recordings (Custodero, 2006; Barrett, 2009, 2011). This body of work has revealed that parents do value music in interactions with their children (Dai and Schader, 2002; Mehr, 2014; Cho, 2015), that music is used in routines, for social bonding, and in identity formation (Barrett, 2009, 2011), and that infants and children encounter music from a wide variety of sources (e.g., toys, singing, and recordings; Young, 2008). Recently, day-long at-home recordings have shown that infants are frequently exposed to live and recorded music, that the distribution of sources of music input is not uniform, and that critical features of music input impact singing development (Costa-Giomi and Benetti, 2020; Mendoza and Fausey, 2021a). Thus, there is increasing evidence that the developmental-ecological approach will lead to novel insights into early music processing.

Understanding language-music interactions will also benefit from the developmental-ecological approach. Current theories about why language and music have similar properties or why they activate the same neural substrates often assume that they share contextual and/or functional roles in human interactions. However, we have little data to empirically test this assumption, particularly in infancy and early childhood when neural specialization develops. For example, a prevalent theory is that both language and music evolved in part to facilitate social bonding (Savage et al., 2021). To support this theory, though, we need data that describes the social contexts in which babies hear language and music in their everyday lives, how babies respond to these stimuli, and how contexts and responses change over time. By describing the similarities and differences in how language and music are experienced in early development, researchers will also be able to form bottom-up hypotheses about cues that infants use to differentiate language and music (Brandt et al., 2012). Thus, a developmental-ecological approach will not only inform our understanding of language and music separately, but also how these domains overlap, separate, and interact across the lifespan.

The developmental-ecological approach will also address challenges faced by researchers investigating these questions from non-developmental perspectives. Below, we describe several prominent roadblocks to understanding language-music interaction and describe how a developmental-ecological approach could address them.

In the past two decades, there has been a surge in naturalistic work in developmental psychology (Yoshida and Smith, 2008; Adolph, 2016; Bulgarelli and Bergelson, 2020; Sullivan et al., 2021) which has yielded several insights into the design and interpretation of naturalistic data. For example, researchers have shown that first-person view head cameras provide a more valid recording of what infants are visually attending to in their environment than traditional third-person recordings (Yurovsky et al., 2013), and others have examined assumptions embedded in hour-long vs. full day recordings (Bergelson et al., 2019; see Mendoza and Fausey, 2021b, for an introduction to thinking through decisions surrounding who, what, where, and how to build and code large, naturalistic corpora). Here, we give recommendations specific to studying the early language and music environment in tandem, from a developmental-ecological perspective.

To fully understand the gene-brain-environment dynamics that give rise to adult cognition, we must have a clearer understanding of the dynamics of the environment in early development. Language-music researchers universally acknowledge that children learn about language and music implicitly, but tend to skirt important questions about how this learning unfolds over time and how the learning process influences downstream processing throughout the lifespan. The developmental-ecological approach offers a path for specifying developmental trajectories and mechanisms that will in turn advance theories of language-music interaction.

EW and DV contributed equally to the article and conceived of the argumentative structure. EW, DL, and DV wrote the text. All authors contributed to the article and approved the submitted version.

This research was supported in part by a grant from the Grammy Museum Foundation.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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