Daniel Willingham--Science & Education
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More on the vocabulary development of toddlers

9/23/2013

 
If you follow education matters you know that the home environment in very early years are vital. One aspect of that home environment is the language infants and toddlers hear at home.

The groundbreaking work of Hart & Risley (1995; replicated by others, e.g. Huttenlocher et al, 2010) showed that socio-economic status of the parents is correlated with vast differences in the amount and complexity of language that children hear at home. 

But what aspect of this speech is important? Does speech need to be directed to children? Perhaps all that’s needed is for children to be in the presence of this more complex language. After all, we know that children do not learn language via instruction; they learn it by observation.

Three studies published in the last couple of years build a convincing case that parents should, indeed, talk to their children. Talking in the presence of their children (but to others) does not confer the same vocabulary benefit.

In the most recent study (Weisleder & Fernald, 2013), experimenters tested 29 Spanish-learning infants at age 19 months. The children wore a small device that made an audio recording of all speech to which the child was exposed. The audio recordings were analyzed by software meant to differentiate speech directed toward the child versus speech audible to the child, but directed to others. A subset of recordings was coded by human observers to ensure the accuracy of the software.

Recordings of a full day’s speech were analyzed and the results showed a huge range in child-directed speech; caregivers in one family spoke over 12,000 words to the child whereas in another family that figure was just 670 words. The amount of child-directed speech as not significantly correlated (r = .17) with the amount of overheard speech.

At 24 months the productive vocabulary of the children was measured by asking the parents to judge words that they believed their child understood and words that their child used.

Of greatest interest, the amount of child-directed speech at 19 months was correlated (r = .57) with vocabulary at 24 months. The amount of overheard speech at 19 months was not (r = .25).
Picture
The sample size in this study is limited and there were some quirky features. (E.g., the software sorting “child-directed” vs. overherd speech is good, but not perfect.) But my confidence in the conclusion is bolstered by reports of the same finding from another lab, investigating speakers of other languages: English (Schneidman et al, 2013) and Yucatec (Schneidman & Goldin-Meadow, 2012).

Why must speech be directed to the child?

Weisleder & Fernald administered another task at 19 months meant to measure word processing efficiency. They speculated that the effect of child-directed speech on vocabulary was mediated through efficiency—something like, for example, the speed and accuracy with which the particular phonemes of the child’s language are processed.

This doesn’t fully explain the difference between child-directed and overheard speech. The obvious hypothesis is that other cues (e.g. eye gaze direction) prompt greater attention to speech that is child-directed, and that attention is necessary to build efficiency.

More details will have to await further research. For now, we can say with greater confidence “talk to your children” not just “talk in the presence of your children.”

References

Hart, B. M., & Risley, T. R. (1995). Meaningful differences in the everyday experience of young American children. Baltimore, MD: Brookes.

Huttenlocher, J., Waterfall, H., Vasilyeva, M., Vevea, J., & Hedges, L. V. (2010). Sources of variability in children’s language growth. Cognitive Psychology, 61, 343–365.

Shneidman, L. A., Arroyo, M. E., Levine, S., & Goldin-Meadow, S. (2013). What counts as effective input for word learning? Journal of Child Language, 40, 672–686.

Shneidman, L. A., & Goldin-Meadow, S. (2012). Language input and acquisition in a Mayan village: How important is directed speech? Developmental Science, 15, 659–673.

Weisleder, A. & Fernald, A. (2013). Talking to children matters: Early language experience strengthens processing and builds vocabulary. Psychological Science, DOI: 10.1177/0956797613488145


José Jorge
9/23/2013 05:13:55 am

Professor Willingham, besides your books (which I devoured by the way, congratulations) Could you indicate for an economist some books that you consider a good introduction to the literature of cognitive psychology? Especially the one related with education? Thank you very much!

Dan Willingham
9/23/2013 11:18:22 pm

Thanks Jose! Tons of really good books on cog psyc--Pinker's "how the mind works" is a little dated, but still good. Almost all of the introduction to cog psych textbooks are good but are, of course, kinda dry. applications of cog psych to edu, there's less on that. There is this book
http://eric.ed.gov/?id=ED439154
but I find it kind of removed from the classroom

what is the best nasal decongestant link
10/12/2013 12:05:19 am

Not so bad for you Jose!

EB
9/23/2013 05:57:03 am

These findings are in alignment with common sense. Otherwise, exposure to TV shows would help a lot with general vocabulary, and I know of no study that indicates that it is.

Also, when adults are speaking to children rather than merely in their presence, their speech can be calibrated to the probable ability of the child to understand, which must be of some help in helping the child actually learn.

Dan Willingham
9/23/2013 11:14:50 pm

EB--there are some studies showing learning vocab from some educ programs (Sesame Street, e.g.) but in general, yes!

Della Palacios, M.Ed. link
9/23/2013 06:24:56 am

Jose, in regards to cognitive science and literacy, here is my page of suggested readings for those who teach literacy... http://www.pinterest.com/sensablelrning/must-reads-if-you-teach-reading/ All books and articles have evidence based in cognitive science. (As a culture, we generally lead children along a highly inefficient and confusing road to literacy. Some learn in spite of the road and others become terribly lost.)

Dan, I'm becoming more of a fan with every bit of writing I read on your blog.

Shortly before Tata’s (my great aunt’s) passing, I took my daughters who were two and three at the time to visit her in the hospital. She told me she had a dream that my girls knew all of their nursery rhymes. Shamefully, I thought, "They don't."

Then, about a year after my Tata passed, I learned an early literacy/ Montessori-minded program for my children. It amazed me how effortlessly and seamlessly they developed literacy skills. So I did what I do when I become interested in a subject- I read veraciously. Over and over,I read of the importance of nursery rhymes.

Our grandparents were wise. Teach children nursery rhymes.

Young learners need to learn abstract concepts using concrete methods. Nursery rhymes must be learned face to face, human to human. Concrete learning involves incorporating modalities, and the more senses involved in the process, the better the outcomes! Patricia Kuhl's research explains through her research why babies need a human talking to them to take their statistics. http://www.ted.com/talks/patricia_kuhl_the_linguistic_genius_of_babies.html *Talking screens do not have the same impact on the mind of the young listener.*

It is in loving memory of Tata, I am proud to say my children now know their nursery rhymes and many, many other children do as well.

Dan Willingham
9/23/2013 11:20:01 pm

Thanks Della :)

pontificatrix
9/23/2013 07:29:40 am

Productive vocabulary was measured *by parent report*? One might imagine that parents who direct more speech towards their children might also be more attuned to the child's speech and thus more likely to recognize the words.

Vocabulary would need to be measured by an objective observer for this study to have any merit.

Dan Willingham
9/23/2013 11:28:06 pm

I agree direct observation would be better, but the measure they used (MacArthur-Bates Communicative Development Inventory) has been validated against observation.
http://onlinelibrary.wiley.com/doi/10.1111/j.1467-8624.2005.00882.x/full
It's not perfect, but it's not terrible.

Victor K
9/23/2013 04:37:32 pm

Quantity of parent-to-child speech likely has large correlation with all other aspects of parental attention (diet, affection, provision of health care, etc.). Are there studies that control for all these to isolate the effect of directed speech on development?

Dan Willingham
9/23/2013 11:30:38 pm

Victor, I don't have the citation at my fingertips, but yes. In this study they tried to eliminate the most important usual suspect by focusing solely on low-income families.

Philip Hand link
9/23/2013 06:39:13 pm

What?! Hang on a minute, this is a perfect and pure example of the correlation=causation fallacy. I don't get why a presumably competent researcher would ever write this:
"the amount of child-directed speech at 19 months was correlated...we can say with greater confidence “talk to your children”"

Seriously, if an undergrad wrote that, you'd smack them upside the head!

Yeah, it fits with common sense, but I can think of any number of stories that would explain the correlation without there being a causal link.
Speech directed toward the child is likely to be more at the child's level, so perhaps those children gained more vocab through exposure to correctly pitched language.
If you're directing speech towards a child, you'll also be getting speech back from the child, so perhaps improved vocab is caused by more production practice, not more listening.
Speech directed towards a child correlates with attention, so perhaps children who get more attention learn more generally.
Etc., etc., etc.

This is just bizarre overinterpretation of empirical results.

Ray
9/26/2013 06:22:50 am

Sigh! Non-scientists sometimes get so excited upon learning that correlation does not equal causation, that they mistakenly assume that all scientific research is about establishing causation. In fact, it is rare that we are able to establish an absolute and immutable chain of causation.

Please note that the researchers do not say anything about causation. They simply note the correlation, and suggest that this can lead to a somewhat greater confidence about the suggestion that parents should talk to their children.

Medical researchers, for example, establish the effectiveness of various drugs through correlations confirmed by the "gold standard" of tests involving double blind random assignment. They may or may not be able to establish the cause of the drug's effectiveness.

Dan Willingham
9/23/2013 11:39:16 pm

Philip--on the one hand, sure, you're right. (These are correlational data. This is such a popular research area that someone has prob. tried to get at causality with structural equation modelling--I don't know offhand.)
I didnt mention it in the blog, but the researchers controlled for child vocalizations and the effect still held.
More generally, if you ever hope to have practical take-aways from this sort of research you'll very seldom get anyway if you wait for an RCT to nail things down. In this case, I don't think you'd want to tell parents "talk to your 8-month old. .or try to elicit talk from your 18 month old w/o necessarily talking to him. . .or talk to your spouse, but using the type of speech you'd use with an 18 month old. . "
Sure there are risks in drawing conclusions based on correlational data, but the risks should be evaluated.

Dan Willingham
9/25/2013 02:19:54 am

I just inadvertently deleted a comment by Roger Sweeny--sorry Roger! Here it is:
"Related to what Philip Hand said, I wonder if they did anything to control for cognitive ability. I ask because I seem to remember a boatload of studies from decades ago showing that babies who had a lot of positive interactions with their parents were happier, better behaved, etc. This was interpreted as showing that more positive interactions would make a happier, better behaved baby. But eventually researchers discovered that much of the causation was in the other direction. Babies with a more positive temperament elicited more positive reactions.

I wonder how much smart infants react in ways that encourage the people around to talk to them. Certainly if they are more responsive to words, the people around are more likely to direct words at them."

Danny M.
9/25/2013 05:43:11 am

Roger/Philip, I agree. When I studied linguistics I would read about how non-linguists would take a domain-general approach to language acquisition and ultimately show only correlational findings, not causative findings. Dan, earlier you mentioned How the Mind Works by Steven Pinker--his book "The Language Instinct" is another top-notch book that explains how language acquisition is innate (i.e. via universal grammar).

In regards to vocabulary development, I am still not convinced about infant-directed speech (IDS). IF there are any positive linguistic benefits to IDS, it is ONLY in the realm of vocabulary and small. And yes, the language "directed" at infants is often motherese and at a child's level, yet each and every typical developing child acquires language perfectly and more or less in a timely manner. Though exposing a child to "more academic" vocab is important, I'm not wholly convinced that directing that language at them gives them a benefit.

Deirdre Mundy link
9/28/2013 04:07:27 am

Plus, by three or so, children CAN pick up vocabulary from things like television shows. (Perhaps there's a difference between child-directed and non-child directed TV?) A three year old who watches a steady diet of Wild Kratts and David Attenborough documentaries can often talk about adaptations and ecosystems... and apply that vocabulary to new situations, too.

Again, it might be correlation-- maybe only certain kinds of small children can learn vocabulary from educational TV and apply it to new situations--- but it does make me wonder how important the 'child directed' effect actually is.


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