Bilingualism in the Early Years: What the Science Says

Abstract

Many children in North America and around the world grow up exposed to two languages from an early age. Parents of bilingual infants and toddlers have important questions about the costs and benefits of early bilingualism, and how to best support language acquisition in their children. Here, we separate common myths from scientific findings to answer six of parents' most common questions about early bilingual development.

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Bilingualism in the Early Years: What the Science Says
Krista Byers-Heinlein, Concordia University
Casey Lew-Williams, Northwestern University
ABSTRACT
Many children in North America and around the world grow up exposed to two lan-
guages from an early age. Parents of bilingual infants and toddlers have important
questions about the costs and benets of early bilingualism, and how to best sup-
port language acquisition in their children. Here, we separate common myths from
scientic ndings to answer six of parents’ most common questions about early
bilingualdevelopment.
Bilingualism in the Early Years: What the Science Says
Bilingual parents are vocal in their desire to raise procient, dynamic bilingual
children. They have questions, and they want answers. But there is a compli-
cated history of positive and negative press about raising children in bilingual
households, to the point where some pediatricians—even today—recommend against
exposing children to two languages. Attitudes against early bilingualism are often
based on myths and misinterpretations, rather than scientic ndings. Here, we aim
to address the most frequently asked questions about childhood bilingualism using
research ndings from a variety of scientic elds including developmental psychol-
ogy, cognitive psychology, education, linguistics, and communication sciences and
disorders. This article is intended for parents and the many people who parents turn
to for advice about fostering successful bilingual development: preschool teachers,
elementary teachers, pediatricians, and speech-language pathologists.

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Bilingualism refers to the ability to use two languages in everyday life. Bilingualism is
common and is on the rise in many parts of the world, with perhaps one in three people
being bilingual or multilingual (Wei, 2000). Contact between two languages is typical
in regions of many continents, including Europe (Switzerland, Belgium), Asia (India,
Philippines), Africa (Senegal, South Africa), and North America (Canada). In the United
States, a large (and growing) number of bilinguals live in California, Texas, Florida, New
York, Arizona, and New Mexico. In California, for example, by 2035, it is expected that
over 50% of children enrolled in kindergarten will have grown up speaking a language
other than English (García, McLaughlin, Spodek, & Saracho, 1995). Similarly, in some
urban areas of Canada such as Toronto, up to 50% of students have a native language
other than English (Canadian Council on Learning, 2008).
Despite the prevalence of bilingualism, surprisingly little research has been con-
ducted on the topic, particularly on the foundations of bilingual language learning in
infants and toddlers. The science of bilingualism is a young eld, and denitive answers
to many questions are not yet available. Furthermore, other questions are impossible
to answer due to vast dierences across families, communities, and cultures. But with
an accumulation of research studies over the last few decades, we are now equipped to
partially answer some of parents’ most pressing questions about early bilingualism.
There are few venues for communicating scientic ndings about early bilingualism
to the public, and our goal is to distill bilingual and developmental science into practi-
cal, accessible information. We are researchers who study bilingual infants and children,
and as such, we interact with bilingual families regularly. When we give community
talks to preschools and nonprot organizations about language development in early
childhood, the question-and-answer period is invariably dominated by questions
about early bilingualism. The consistency in questions is astonishing. Are bilingual chil-
dren confused? Does bilingualism make children smarter? Is it best for each person to
speak only one language with a bilingual child? Should parents avoid mixing languages
together? Is earlier better? Are bilingual children more likely to have language dicul-
ties, delays, or disorders? This article is organized around these six common questions.
1. Are bilingual children confused?
One of the biggest concerns that parents have about raising children in a bilingual
household is that it will cause confusion. But is there any scientic evidence that young
bilinguals are confused? The rst question to ask is what confusion would look like.
Except in the case of neurological disorders (Paradis, 2004), uently bilingual adults can

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Bilingualism in the Early Years: What the Science Says
speak whatever language they choose in the moment, and are clearly not confused. But
what about bilingual children and infants?
One misunderstood behavior, which is often taken as evidence for confusion, is
when bilingual children mix words from two languages in the same sentence. This is
known as code mixing. In fact, code mixing is a normal part of bilingual development,
and bilingual children actually have good reasons to code mix (Pearson, 2008). One rea-
son some children code mix is that it happens frequently in their language communi-
ties—children are just doing what they hear adults around them do (Comeau, Genesee,
& Lapaquette, 2003). A second reason is that, just like young monolinguals, young bilin-
guals are sometimes limited in their linguistic resources. Similarly to how a monolin-
gual 1-year-old might initially use the word “dog” to refer to any four-legged creature,
bilingual children also use their limited vocabularies resourcefully. If a bilingual child
does not know or cannot quickly retrieve the appropriate word in one language, she
might borrow the word from the other language (Lanza, 2004). Rather than being a sign
of confusion, code mixing can be seen as a path of least resistance: a sign of bilingual
children’s ingenuity. Further, bilingual children do not seem to use their two languages
haphazardly. Even 2-year olds show some ability to modulate their language accord-
ing to the language used by their conversational partner (Genesee, Boivin, & Nicoladis,
1996). There is also evidence that children’s early code mixing adheres to predictable
grammar-like rules, which are largely similar to the rules that govern adults’ code mix-
ing (Paradis, Nicoladis, & Genesee, 2000).
What about bilingual infants? Again, the research is clear: bilingual infants readily
distinguish their two languages and show no evidence of confusion. Languages dif-
fer on many dimensions—even if you don’t speak Russian or Mandarin, you can likely
tell one from the other. Infants are also sensitive to these perceptual dierences, and
are particularly attuned to a language’s rhythm. Infants can discriminate rhythmically
dissimilar languages like English and French at birth (Byers-Heinlein, Burns, & Werker,
2010; Mehler et al., 1988), and by age 4 months they can tell even rhythmically similar
languages like French and Spanish apart (Bosch & Sebastián-Gallés, 1997, 2001; Nazzi,
2000). Bilingual infants may be even more sensitive than monolinguals when it comes
to discriminating languages. Recent research has shown that 4-month- old monolingual
and bilingual infants can discriminate silent talking faces speaking dierent languages
(Weikum et al., 2007). However, by 8 months of age, only bilinguals are still sensitive to
the distinction, while monolinguals stop paying attention to subtle variations in facial
movements (Sebastián-Gallés, Albareda-Castellot, Weikum, & Werker, 2012; Weikum et
al., 2007). Instead of being confused, it seems that bilingual infants are sensitive to infor-
mation that distinguishes their languages.

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2. Does bilingualism make children smarter?
Popular books such as The Bilingual Edge (King & Mackey, 2009), and articles such as
The Power of the Bilingual Brain (TIME Magazine; Kluger, 2013) have touted the potential
benets of early bilingualism. One of the most important benets of early bilingual-
ism is often taken for granted: bilingual children will know multiple languages, which
is important for travel, employment, speaking with members of one’s extended fam-
ily, maintaining a connection to family culture and history, and making friends from
dierent backgrounds. However, beyond obvious linguistic benets, researchers have
investigated whether bilingualism confers other non-linguistic advantages (Akhtar &
Menjivar, 2012).
Several studies have suggested that bilinguals show certain advantages when it
comes to social understanding. In some ways, this is not surprising, as bilinguals must
navigate a complex social world where dierent people have dierent language knowl-
edge. For example, bilingual preschoolers seem to have somewhat better skills than
monolinguals in understanding others’ perspectives, thoughts, desires, and intentions
(Bialystok & Senman, 2004; Goetz, 2003; Kovács, 2009). Young bilingual children also
have enhanced sensitivity to certain features of communication such as tone of voice
(Yow & Markman, 2011).
Bilinguals also show some cognitive advantages. In particular, bilinguals appear to
perform a little bit better than monolinguals on tasks that involve switching between
activities and inhibiting previously learned responses (Bialystok, Craik, & Luk, 2012).
Although these advantages have been mostly studied in bilingual adults (Costa,
Hernández, & Sebastián-Gallés, 2008) and children (Bialystok & Martin, 2004), new
evidence suggests that even bilingual infants (Kovács & Mehler, 2009a, 2009b) and
toddlers (Poulin-Dubois, Blaye, Coutya, & Bialystok, 2011) show cognitive advantages.
Additionally, there is some evidence that bilingual infants are advantaged in certain
aspects of memory, for example generalizing information from one event to a later
event (Brito & Barr, 2012).
Research has not been able to determine exactly why these advantages arise,
but there are several possibilities. Bilingual adults have to regularly switch back and
forth between their languages, and inhibit one language while they selectively speak
another. Some researchers suspect that this constant practice might lead to certain
advantages by training the brain (Green, 1998). Amongst infants, the need to constantly
discriminate their two languages could also play a role (Sebastián-Gallés et al., 2012).
However, it is important to note that bilingualism is not the only type of experience that

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Bilingualism in the Early Years: What the Science Says
has been linked to cognitive advantages. Similar cognitive advantages are also seen
in individuals with early musical training (Schellenberg, 2005), showing that multiple
types of enriched early experience can promote cognitive development. Regardless
of origin, it should be noted that the “bilingual advantage” has sometimes been over-
played in the popular press. So far, bilingual cognitive advantages have only been
demonstrated using highly sensitive laboratory-based methods, and it is not known
whether they play a role in everyday life. Thus, the reported advantages do not imply
that bilingualism is an essential ingredient for successful development.
3. Is it best for each person to speak only one language
with a bilingual child?
One popular strategy for raising bilingual children is “one-person-one-language,”
a strategy rst recommended over 100 years ago (Ronjat, 1913). Theorists originally
reasoned that associating each language with a dierent person was the only way to
prevent bilingual children from “confusion and intellectual fatigue.” While appealing,
this early notion has been proven false. As discussed above, there is no evidence that
bilingual children are confused by early bilingualism, and the cognitive benets associ-
ated with bilingualism run counter to the notion of “intellectual fatigue.”
It is still important to consider what strategies families can use to promote early bilin-
gual development. Research has shown that a one-person-one-language approach can
lead to successful acquisition of the two languages (Barron-Hauwaert, 2004), but that
it does not necessarily lead to successful acquisition of the two languages (De Houwer,
2007). Further, children who hear both languages from the same bilingual parent often
do successfully learn two languages (De Houwer, 2007). A one-person-one-language
approach is neither necessary nor sucient for successful bilingual acquisition.
Several other factors have proven to be important to early bilingual development.
These factors might lead some families to use a one-person-one-language strategy,
and other families to use other strategies. First, it is important to remember that infants
learn language through listening to and interacting with dierent speakers. Infants
need to have a lot of exposure to the sounds, words, and grammars of the languages
that they will one day use. Both quality and quantity matter. High quality language
exposure involves social interaction—infants do not readily learn language from televi-
sion (DeLoache et al., 2010; Kuhl, Tsao, & Liu, 2003), and low-quality television view-
ing in infancy has been linked to smaller vocabulary sizes in bilingual toddlers (Hudon,
Fennell, & Hofty zer, 2013). Opportunities to interac t with multiple dierent speakers has
been linked to vocabulary learning in bilingual toddlers (Place & Ho, 2010).

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Quantity can be measured by the number of words that children hear per day in
each language. Quantity of early exposure has a profound eect on children’s ongoing
language development: hearing more words gives children a greater opportunity to
learn a language, which leads to later advantages in school performance (Hart & Risley,
1995). For bilingual children, it is important to consider the quantity of their exposure
to each language. While a bilingual’s two languages do inuence each other to a cer-
tain degree (Döpke, 2000), in many ways they travel on independent developmental
paths. Bilingual children who hear a large amount of a particular language learn more
words and grammar in that language (Ho et al., 2012; Pearson & Fernández, 1994),
and show more ecient processing of that language (Conboy & Mills, 2006; Hurtado,
Grüter, Marchman, & Fernald, 2013; Marchman, Fernald, & Hurtado, 2010). Bilingual par-
ents thus need to ensure that their children have sucient exposure to the languages
they want their children to learn. We return to this topic in the next sections.
Relatively balanced exposure to the two languages is most likely to promote suc-
cessful acquisition of both of the languages (Thordardottir, 2011). In situations where
each parent spends equal time with a child, one-parent-one-language can be a great
way to ensure equal exposure. Conversely, exposure to a second language only when
grandma and grandpa visit on the weekend, or when a part-time nanny visits on a few
weekdays, or when a language class meets on Thursday nights, will not lead to bal-
anced exposure. Imagine an average infant who sleeps about 12 hours a day, and so is
awake 84 hours per week. A single afternoon (~ 5 hours) is only about 6% of the child’s
waking life, and this exposure alone is unlikely to lead to acquisition of a language.
Similarly, in homes where one parent is the primary caregiver, a one-parent-one-lan-
guage is unlikely to lead to balanced exposure.
Unfortunately, providing perfectly balanced exposure in the early years will not nec-
essarily ensure later bilingualism. As children become older, they become more aware
of the language spoken in the community where they live, and are likely to use this
language at school. This is known as the majority language, while other languages that
are not as widely spoken are known as minority languages. Even if initially learned in
preschool, minority languages are much more likely than majority languages to be lost
as development continues (De Houwer, 2007). Many experts recommend providing
slightly more early input in a minority than in a majority language, and where possible
providing children with opportunities to play with other kids in that language (Pearson,
2008). Raising a bilingual child in communities that are largely bilingual such as Miami
(Spanish-English), Montreal (French-English), and Barcelona (Catalan-Spanish) provides
fewer challenges for ensuring the ongoing use of the two languages.

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So what language strategies should parents use? The best answer is that parents
should use whatever strategy promotes high-quality and high-quantity exposure to
each of their child’s languages. This could include structured approaches such as using
dierent languages as a function of person (one-person-one-language), place (one lan-
guage at home, one language outside), or time (alternating days of the week, or morn-
ings/afternoons). Some parents insist on speaking only one language with their child,
even if they are able to speak the other (Lanza, 2004), to ensure exposure to a particular
language. Other families nd that exible use of the t wo languages, without xed rules,
leads to balanced exposure and positive interactions. Each family should consider the
language prociency of each family member as well as their language preference, in
conjunction with their community situation. Families should regularly make an objec-
tive appraisal of what their child is actually hearing on a daily basis (rather than what
they wish their child was hearing), and consider adjusting language use when necessary.
4. Should parents avoid mixing languages together?
Many parents of bilingual children are bilingual themselves (Byers-Heinlein, 2013).
Code mixing—the use of elements from two dierent languages in the same sentence
or conversation—is a normal part of being a bilingual and interacting with other bilin-
gual speakers (Poplack, 1980). Code mixing is relatively frequent amongst bilingual
parents as well (Byers-Heinlein, 2013), and even parents who have chosen a one-parent-
one-language strategy still code mix from time to time (Goodz, 1989). But what eects
does hearing code mixing have on the development of bilingual children?
Research on the impact of code mixing on bilingual children’s development is still
quite limited. One study of 18- and 24-month-olds found that high amounts of code
mixing by parents was related to smaller vocabulary sizes (Byers-Heinlein, 2013).
However, other studies have found no relationship between code-mixed language
and early language development (Place & Ho, 2011). Further, studies are beginning
to reveal that bilingual children as young as 20-months are able to understand code-
mixed sentences, and show similar processing patterns as bilingual adults (Byers-
Heinlein, 2013). This would suggest that bilinguals are able to cope with code mixing
from an early age. It has also been suggested that while code mixing might make word
learning initially dicult, it is possible that practice switching back and forth between
the languages leads to later cognitive benets (Byers-Heinlein, 2013). Unfortunately, the
jury is still out on whether exposure to code mixing has developmental consequences
for bilingual children, but we are currently working on several research projects that will
help answer this question.

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It is important to note that considerations of code mixing also have important social
implications. In some communities, code mixing is an important part of being bilin-
gual and being part of a bilingual community. For example, code mixing is the norm
in some Spanish-English communities in the U.S., and Afrikaans-English code mixing is
the norm in some parts of South Africa. Dierent communities have dierent patterns
of and rules for code mixing (Poplack, 1984), and children need exposure to these pat-
terns in order to learn them.
5. Is earlier better?
Many people are familiar with the concept of a “critical period” for language acquisi-
tion: the idea that humans are not capable of mastering a new language after reaching
a certain age. Researchers disagree about whether a critical period exists at all, and
they disagree about when this critical period may occur—proposals range from age 5
to 15 (Krashen, 1973; Johnson & Newport, 1989; Lenneberg, 1967). Disagreement aside,
research on bilingualism and second language learning converges robustly on a simple
take-home point: earlier is better. There may not be a sharp turn for the worse at any
point in development, but there is an incremental decline in language learning abilities
with age (Birdsong & Molis, 2001; Hakuta, Bialystok, & Wiley, 2003).
This point is best understood as an interaction between biological and environmen-
tal factors. Researchers have argued that biological change during the rst two decades
of life results in a reduced capacity for learning and retaining the subtleties of language
(Johnson & Newport, 1989; Weber-Fox & Neville, 2001). In other words, our brains may
be more receptive to language earlier in life. But importantly, our environment is also
more conducive to language learning earlier in life. In many cultures and in many fami-
lies, young children experience a very rich language environment during the rst years
of life. They hear language in attention-grabbing, digestible bundles that are targeted
skillfully at their developmental level (Fernald & Simon, 1984). Caregivers typically
speak in ways that are neither too simple nor too complex, and children receive hours
and hours of practice with language every day. This high-quality and high-quantity
experience with language—a special feature of how people communicate with young
children—often results in successful language learning. It gives children rich, diverse,
and engaging opportunities to learn about the sounds, syllables, words, phrases, and
sentences that comprise their native language. But beyond the rst years of life, second
language learning often happens ver y dierently. Older children and adults do not usu-
ally have the same amount of time to devote to language learning, and they do not
usually experience the advantage of fun, constant, one-on-one interaction with native
speakers. Instead, they often nd themselves in a classroom, where they get a small

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Bilingualism in the Early Years: What the Science Says
fraction of the language practice that infants and toddlers get (Lew-Williams & Fernald,
2010). In classrooms, words are dened for them and grammar is described to them.
Dening and describing can be eective, but they are not as powerful as discovering
language from the ground up.
Applied to bilingualism, these maturational and environmental dierences between
younger and older learners indicate that it is most advantageous to learn two lan-
guages early on in life. Bilinguals who learn two languages from birth are referred to
as simultaneous bilinguals, and those who learn a rst language followed by a second
language—whether as toddlers or as adults—are referred to as sequential bilinguals.
The evidence points to fairly robust advantages for simultaneous bilinguals relative to
sequential bilinguals. They tend to have better accents, more diversied vocabulary,
higher grammatical prociency, and greater skill in real-time language processing. For
example, children and adults who learn Spanish as a second language typically strug-
gle to master Spanish grammatical gender (e.g., “is it el gato or la gato?”), while people
who learn Spanish and English from birth show reliable and impressive ease in using
grammatical gender (Lew-Williams & Fernald, 2007, 2010).
However, parents should not lose hope if they have not exposed their children to
each language from birth. Infants’ brains and learning environments are special and
non-recreatable, but there are many other ways to foster bilingual development. Here
we overview two possibilities. First, some parents (particularly those who can aord
childcare) choose to hire bilingual nannies or send children to bilingual preschools,
in order to maximize their children’s exposure to another language. This can certainly
result in increased bilingual prociency, but it is essential to provide continued oppor-
tunities to practice each language once the child is older. Parental expectations should
be quite low if children do not have opportunities to continue learning and using a
language throughout development. However, keep in mind that bilingual exposure
does not necessarily translate to being a bilingual who is able to understand and speak
a language uently. Researchers generally consider a child to be bilingual if he or she
receives at least 10-25% of exposure to each language (Byers-Heinlein, under review;
Place & Ho, 2011; Marchman et al., 2010; Marchman, Martínez-Sussmann, & Dale,
2004), but this level of exposure by no means guarantees functional bilingualism (De
Houwer,2007).
Second, there are language immersion programs in elementary schools in many of
the world’s countries, including the U.S. and Canada. Their goal is to promote bilin-
gualism, biliteracy, and multicultural prociency among both language-majority and
language-minority students. In the U.S., hundreds of immersion programs have been

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Krista Byers-Heinlein and Casey Lew-Williams
established in the last four decades in such languages as Spanish, French, Korean,
Cantonese, Japanese, Mandarin, Navajo, and Hebrew. There are currently 434 or more
immersion programs in 31 U.S. states (Center for Applied Linguistics, 2011). French
immersion programs are available in all 10 Canadian provinces, with enrolment ranging
from 2-32% of students depending on the province (Statistics Canada, 2000). Immersion
programs confer advantages over other formats of language instruction that are typical
in high school and college classrooms. In immersion programs, the second language is
not necessarily a topic of instruction, but a vehicle for instruction of other curriculum
subjects. In terms of the quantity of language exposure, immersion classrooms do not
rival infants’ language environments. However, they often foster functional bilingual-
ism, and equip children with language skills that help them in later educational and
professional contexts.
The take-home messages about bilingual language exposure are clear: more is bet-
ter, and earlier is better. If you are 75 years old and you have always wanted to learn
Japanese, start now. Language learning becomes more challenging with time, for both
maturational and environmental reasons, but for those who are motivated (Gardner &
Lambert, 1959), it is never too late to learn a new language.
6. Are bilingual children more likely to have language diculties, delays,
or disorders?
Bilingual children are not more likely than monolingual children to have diculties
with language, to show delays in learning, or to be diagnosed with a language disorder
(see Paradis, Genesee, & Crago, 2010; Petitto & Holowka, 2002). Parents’ perceptions are
often otherwise—they feel that their child is behind due to their bilingualism—reveal-
ing an interesting disconnect from scientic ndings. Science has revealed an impor-
tant property of early bilingual children’s language knowledge that might explain this
misperception: while bilingual children typically know fewer words in each of their
languages than do monolingual learners of those languages, this apparent dierence
disappears when you calculate bilingual children’s “conceptual vocabulary” across both
languages (Marchman et al., 2010). That is, if you add together known words in each
language, and then make sure you don’t double-count cross-language synonyms (e.g.,
dog and perro), then bilingual children know approximately the same number of words
as monolingual children (Pearson, Fernández, & Oller, 1993; Pearson & Fernández, 1994).
As an example, if a Spanish/English bilingual toddler knows 50 Spanish words and
50 English words, she will probably not appear to be as good at communicating when
compared to her monolingual cousin who knows 90 English words. However, assuming

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Bilingualism in the Early Years: What the Science Says
10 of the toddler’s Spanish words are also known in English, then the toddler has a
conceptual vocabulary of 90 words, which matches that of her cousin. Even so, know-
ing 50 vs. 90 English words could result in noticeably dierent communication abilities,
but these dierences are likely to become less noticeable with time. This hypotheti-
cal example about equivalence in vocabulary is supported by research showing that
bilingual and monolingual 14-month-olds are equally good at learning word-object
associations (Byers-Heinlein, Fennell, & Werker, 2013). This oers some reassurance that
young bilinguals—like young monolinguals—possess learning skills that can success-
fully get them started on expected vocabulary trajectories. There is also evidence that
bilingual children match monolinguals in conversational abilities; for example, when
somebody uses a confusing or mispronounced word, or says something ambiguous,
bilingual children can repair the conversation with the same skill as monolinguals
(Comeau, Genesee, & Mendelson, 2010).
Just like some monolingual children have a language delay or disorder, a similar pro-
portion of bilinguals will have a language delay or disorder. Evidence that one bilingual
child has a language diculty, however, is not evidence that bilingualism leads to lan-
guage diculties in general. The challenge for pediatricians and for speech-language
pathologists is to decide if a bilingual child does have a problem, or whether her errors
are part of normal development and interaction between the sounds, words, and
grammars of her two languages. If parents are worried that their bilingual child does
have a delay, they should rst consult their pediatrician. Pediatricians sometimes have
a tendency to say, “Don’t worry, her language is completely normal.” This statement
will end up being false for some children who will end up diagnosed with language
diculties, but it is more likely than not to be true, especially considering that parents
can be inaccurate when estimating their bilingual child’s language skills. In some other
cases, health care providers with concerns about language impairment may recom-
mend against raising a child in a bilingual environment. This recommendation is not
supported by the science of bilingualism. Bilingual children with specic language
impairments (Paradis, Crago, Genesee, & Rice, 2003), Down syndrome (Kay-Raining Bird
et al., 2005), and autism spectrum disorders (Peterson, Marinova-Todd, & Mirenda, 2012)
are not more likely to experience additional delays or challenges compared to monolin-
gual children with these impairments.
If parents do not feel comfortable with a pediatrician’s opinion, they should nd (or
ask for a referral to) a speech-language pathologist with expertise in bilingualism, if at
all possible. Early intervention increases the likelihood of a positive outcome. The prob-
lem is that few clinicians receive quality training about the learning needs of bilingual
children, which in some cases leads to a misdiagnosis of bilingual children as having

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Krista Byers-Heinlein and Casey Lew-Williams
delayed or disordered language (Bedore & Peña, 2008; Kohnert, 2010; Thordardottir,
Rothenberg, Rivard, & Naves, 2006). The time is past due to eliminate such simple mis-
understandings in clinical settings. A bilingual clinician, or an individual who has train-
ing in bilingualism, will take care in assessing language skills in both languages, in order
to measure the child’s entire language prole. Parents should keep in mind that clini-
cians have a very dicult job when it comes to assessing bilingual children. They have
to (1) accurately assess a bilingual child’s language abilities in each of her languages,
(2) integrate the child’s problematic and unproblematic abilities in terms of sounds,
words, grammar, and conversation in each language into a coherent whole, (3) evaluate
whether the child is delayed and/or disordered in one or both languages, (4) weigh the
child’s linguistic/cognitive capacities in comparison to typically and atypically devel-
oping monolingual children and, when possible, bilingual children of the same age,
and (5) develop an eective intervention that targets subareas of linguistic/cognitive
competence in one and/or both languages. This is a tangled landscape for intervention,
but one that can be assessed thoughtfully. Regardless of whether parents pursue inter-
vention, they can help children gain bilingual prociency by using both languages as
regularly as possible in enriching and engaging contexts. Furthermore, parents should
keep in mind that both monolingual and bilingual children can best show o their skills
when using language that matches their daily experiences (Mattock, Polka, Rvachew, &
Krehm, 2010).
In summary, if you measure bilinguals using a monolingual measure, you are more
likely to nd false evidence of delay. Fortunately, researchers and clinicians are now
developing bilingual-specic measures that paint a more accurate picture of bilinguals’
global language competence.
Conclusions
In this article, we have reviewed what the science says about six of parents’ most
commonly asked questions about early bilingualism. Research demonstrates that we
need to reshape our views of early bilingualism: children are born ready to learn the
language or languages of their environments without confusion or delay (Werker &
Byers-Heinlein, 2008). To promote successful bilingual development, parents raising
bilingual children should ensure that their children have ample opportunities to hear
and speak both of their languages. As children get older, interacting with monolingual
speakers (especially other children) is important for motivating ongoing language use,
especially for minority languages not widely spoken in the community (Pearson, 2008).

LEARNing Landscapes | Vol. 7, No. 1, Autumn 2013 | 107
Bilingualism in the Early Years: What the Science Says
Teachers, pediatricians, and speech language pathologists play an important role in
dispelling common myths, and in communicating science-based information about
early bilingualism to parents.
While our focus here has been on language development, it is also important to rec-
ognize that early childhood is also a time of profound emotional, social, physical, and
cognitive development. Bilingualism will be a priority or even a necessity for some fam-
ilies. Other families might choose to focus on other aspects of development. In some
cases, where families are not uent in a second language, early bilingualism might be
unrealistic. Here, it is important to keep two things in mind: 1) bilingualism is only one
way to promote successful early development, and 2) second language learning is pos-
sible at any age. Language—any language—is a window to the world. It is better for
parents to provide plenty of input and interaction in a language they are comfortable
in, than to hold back because they are not uent or comfortable in the language.
When it comes to raising bilingual children, myths and misunderstandings are com-
mon, but facts are hard to come by. Together with researchers around the world, we are
working hard to continue providing scientically based facts addressing parents’ most
important questions about early bilingualism.
Acknowledgments
This work was suppor ted by grants to K rista Byers-Heinlein from the Natural Sciences
and Engineering Council of Canada and the Fonds de recherche du Québec - Société
et culture, and to Casey Lew-Williams from the National Institute of Child Health and
Human Development and the American Speech-Language-Hearing Foundation. Thank
you to Alexandra Polonia for her assistance with proofreading, and to the many parents
of bilingual children whose questions inspire and motivate us.

108 | LEARNing Landscapes | Vol. 7, No. 1, Autumn 2013
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Krista Byers-Heinlein and Casey Lew-Williams
LINK TO:
http://infantresearch.concordia.ca
http://babylab.northwestern.edu
Krista Byers-Heinlein (B.A., McGill University; M.A., Ph.D.,
University of British Columbia) is Assistant Professor in the
Department of Psychology at Concordia University. She directs
the Concordia Infant Research Laboratory, and is a member of
the Centre for Research in Human Development, and the Centre
for Research on Brain, Language and Music. She is recognized
internationally for her research on bilingualism in infancy, and
has published extensively on the topics of bilingual infants’
speech perception and word learning.
Casey Lew-Williams (B.A., University of California, Berkeley;
M.A., Ph.D., Stanford University) is Assistant Professor in the
Department of Communication Sciences and Disorders at
Northwestern University. He directs the Language Learning Lab,
a research group devoted to studying rst, second, and bilin-
gual language learning. His work focuses in particular on under-
standing how dierent learning experiences shape language
outcomes in diverse populations of infants, children, and adults.