On Nature, Nurture, and In Between

Photo Credit: Michael L. Kaufman
Photo Credit: Michael L. Kaufman

So, I’ve been kind of busy. I’ve been doing all kinds of fun stuff, but one that I’m really enjoying (and takes up most of my time now) is teaching an introduction to developmental psychology class. I’m very excited about this opportunity, and I’ve re-discovered how much I love to teach. But my amusement is not the topic today. I’ve been researching articles that are far off my field for this course, and one that I found completely blew my mind, so I’m going to write about it even though it’s fairly “old” for the post-twitter era (published in 2007). In a psychological journal article, this would qualify as “recent research”. So, this might be common knowledge, but I took my intro dev psych in 2002 and my last “genetic bases of developmental disorders” course in 2006, so there you go.

What They Did

The study was a meta-analysis (a study of studies) that examined heritability estimates over time. Heritability estimates are typically arrived at by comparing the correlation between monozygotic (identical) twin-sets and dizygotic (fraternal) twin-sets. The idea is that identical twins share 100% of their genes, so if they are more similar than fraternal twins on a certain measure (say, IQ), than that measure is likely influenced by genes.

This meta-analysis examined several measures, including internalizing and externalizing behaviours (depression and aggression, respectively), as well as IQ and ADHD symptoms. They looked at twins that were measured at least twice, and were between 13 and 25 years old at the time of the first measurement.

What They Found

Externalizing and internalizing behaviours and IQ all increased in heritability as time went by. I’ll say that again. The older the twins were, the more likely the identical twins were to be more similar than the fraternal twins. Is your mind blown yet?

What It Means

If you (like me) were holding the traditional view of how heredity influences development, you probably thought something along the lines of “genes provide the clay and environment does the sculpturing”. In other words, the genes are what you come into the world with, and then the environment does its thing. But this is clearly not the story here. The authors argue that the identical twins, because of their shared genes, are more likely to select similar environments, and the cumulative effect of these environments is what drives this “increase in heritability”. However, an alternative explanation is that some genes are expressed later in life, and these could be driving the increase in similarity. This alternative explanation, by the way, was conceived by a non-geneticist, so it may not actually be correct.

Nature Vs. Nature

I’ve written several posts in which I (lightly) touched on the nature vs. nurture theme. This question is one of the main one in psychology, especially when it comes to development. After all, one of the main reasons to study children is that they give us a window into the kinds of skills we come into the world with. But recent (ha!) research clearly shows that not only both nature and nurture influence development – nature and nurture also influence each other and then these influences influence development. Mind: blown.


Parenting and Self-Regulation

How we influence our children’s behaviour and compliance.
Photo credit:  athomson
Photo credit: athomson

As I was reading “Bringing Up Bébé” (which is a whole other post that I don’t know if I’ll ever write) it struck me that the author assumes that the way French parents behave makes their children more compliant. As a developmental researcher, I of course performed a “scholar search”, and came across several interesting studies. One of them was published a few years ago, and was really interesting.

What they Did

The authors examined the relationship between parenting behaviours and other demographic factors, such as gender and socioeconomic status, and the development of inhibitory control. If you need a refresher on what inhibitory control is and why it’s important, you can read about it here and here. I’ll wait.

So, this study had parents fill out a questionnaire assessing their child’s inhibitory control skills, and their parenting behaviours were assessed by the researchers during a home visit. The question was which variables would affect the initial level of inhibitory control at age 2 years, and which variables would affect the growth of inhibitory control between 2 and 4 years of age.

What They Found

There were two interesting findings about parenting. First, harsh parenting only influenced the initial level of inhibitory control but not the development. That is, harsh parenting was associated with lower levels of inhibitory control at age 2, but not with a slower growth of inhibitory control between the ages 2 and 4. In contrast, supportive parenting was associated with increased growth of inhibitory control over the two-year period, but it was not related with the initial levels.

What it Means

I think that we can combine these findings with what I talked about a few weeks ago regarding the praise we give. I said then that parenting a two-year-old is really different from parenting a four-year-old. As I’m doing both right now, I’m keenly aware of that. There’s a different focus, a different set of expectations, and of course different things “tick us off”. If my two-year-old is unable to follow the post-dinner routine, for example, I remind her and make it into a game. If my four-year-old skips his “duties” (brushing teeth, taking plate off the table, etc.) I’m more likely to get snippy because he should know better by now. So I can see how being patient rather than harsh helps the two-year-olds, but that later on a bit of annoyance isn’t all that harmful (and really quite reasonable). Similarly, I can see how being supportive and involved with the child is a bit over their head at 2, but can go a long way in later years. Of course, I don’t mean you shouldn’t talk to your child until she’s three, but there’s a qualitative difference, I think, between how you approach a similar situation with a two-year-old and with a four-year-old.

You Can’t Always Get What You Want

Photo Credit: asenat29
Photo Credit: asenat29

I wrote before about what developmental scientists call “Theory of Mind” – the ability to reason about others’ mental states, such as desires, beliefs, and intentions. This field of research is endlessly fascinating, as there is so much to learn. One of the hardest things to accommodate is seemingly contradicting findings with different age groups.

Take for example research about desire. A while ago (16 years now), researchers looked into 14- and 18-month-olds’ ability to respect another’s desire that conflicted with their own. An experimenter exhibited “liking behaviours” (saying “yummy”, rubbing her tummy, etc.) towards either goldfish crackers or broccoli. Since 93% of the kids preferred goldfish crackers (naturally), for about half of the kids the experimenter’s preference for broccoli conflicted with their own. Then the experimenter held out her hand and asked, “Can you give me some?”

About 80% of the 14-months-olds gave the experimenter goldfish crackers regardless of her expressed “desire”. However, only 30% of the 18-months-olds gave her goldfish crackers when she showed preference for broccoli. That is, the majority of 18-months-olds were able to respect the experimenter’s preference for broccoli, as weird as they may have thought it was. So, as per the authors, 18-months-olds were able to consider another person’s desire and act on it, despite the conflict with their own preference.

Now, another recent research looked at 3- to 5-year-olds. Cristina Atance is a lovely person and bright researcher working at Ottawa University. Our lab has collaborated with hers and we have a good relationship. She and her graduate student ran a study in which they looked at whether preschoolers can choose a gift for their mom. They showed the kids two items: a stuffed teddy bear and a magazine. There were several copies of each item, like you can see in a store. They asked children what would be a good gift for them and what would be a good gift for their mom. But they changed the order of the questions. So, some of the children first got to choose a gift for themselves and then choose a gift for their mom, whereas some of the children had to choose first for mom and only then for themselves. They also had a condition in which children were told that they will get to choose for themselves later, but they have to choose for mom first (the anticipated satisfaction condition). Turns out that all kids were better at choosing the appropriate gift for mom after they chose (or anticipated choosing) a gift for themselves than they were before they chose a gift for themselves. Most 3-year-olds selected the teddy bear for mom if they had to choose for mom first, but about 50% were able to choose correctly after they chose the teddy bear for themselves. Most 4- and 5-year-olds were better than that, and were able to choose the appropriate gift for mom after they chose a gift for themselves (although their performance when choosing for mom first was lower).

There are a few problems with this study. One of them is the (very) small sample size – there are simply not enough kids in each condition and each age group to really be able to generalize. Another problem (and I think the main one) is with the fact that the verbal instructions for the choose-for-self-first and the anticipated-choosing-for-self were much longer than the last, choose-for-mommy-first condition. “Stop-and-think” paradigms have been well documented to increase preschoolers’ inhibitory control, so it’s possible that the longer verbal instructions provided a long enough “stop and think” time interval for the kids to think about what’s actually appropriate for mom.

But let’s assume that we accept the results of this study as is. How come 18-months-old kids can think about someone else’s desires but they somehow loose this ability when they are 3-years-old? One explanation is that there’s something different in the way we think about food from a very young age. That is, when it comes to food (the objects of “desire” in the first study I discussed) even babies can understand that different people like different things. I suspect that’s not the case, but that’s one difference between the first and second papers I mentioned. Another possibility (and I think this one’s more likely) is that all of the babies’ experience with the experiment in the first study was her intense dislike of goldfish crackers and her intense liking of broccoli. In contrast, 3-year-olds are likely to experience their mom as someone who actually likes teddy bears (because when your toddler brings you a teddy bear, you say “oh, cute teddy!” even if you are only half conscious), and are not very likely to experience their mom as someone who reads magazines (do you know any moms of very young preschoolers who have the time?). Therefore, it only makes sense that the kids were not entirely sure what to do. By the way, I tried this with my own kids, and both said that, between a stuffed zebra and glasses, glasses would be a good present for mommy – despite never seeing me wearing glasses. But they also thought I would like broccoli better than a cupcake (not quite true), at which point the conversation was derailed by requests for cupcakes. Clearly my homemade experiment was not well thought out.

That said, this field of research is really interesting and highly practical. The next time you want to take your preschoolers shopping, promise them they can choose something for themselves at the end, and see if it goes better. I would love to hear the results of that experiment.

Parents and Bullies

Photo Credit:  Chesi - Fotos CC
Photo Credit: Chesi – Fotos CC

A new meta-analysis shows that there is a relationship between parental behaviour and being a bully.

October is National Bullying Prevention Month. Virtually all the parents’ blogs I follow mention bullying at some point of the month. I decided to join in again this year, even though it is not my area of expertise, because this is a good cause, and it’s important that parents know as much as possible about this problem.

A meta-analysis that just came out[*] explored the link between parental behaviours and bullying, and I thought this is the perfect time to talk about it.

What They Did

A meta-analysis is a study of studies. It uses the combined data of published studies to provide an overview of the research question. The advantage of a meta-analysis is that more data (more information) means more power, both statistically and conceptually; we would be more confident accepting a relationship between parental behaviour and bullying if 10 independent studies reached the same conclusion than we would be if only one study found it. A disadvantage of meta-analyses is that they can only investigate questions that other people have already asked. That is, if I think that, for instance, caffeine intake is related to bullying, and no one has studied this relationship (or there is only one study looking at it) I can’t do a meta-analysis. So these authors did a meta-analysis of studies that looked into the relationship between parental behaviour and bullying.

What They Found

The authors report a small but significant relationship between parental behaviour and bullying. That is, positive parental behaviour – such as good communication, warm relationship, and parental involvement were associated with a lower likelihood of being bullied. Negative parental behaviour such as abuse and neglect were (perhaps not surprisingly) associated with a higher likelihood of being bullied and particularly with being a bully/victim, that is, someone who is both a victim of bullying and a bully him/herself. Interestingly, over-protection was associated with an increased likelihood of being victimized.

I thought there were a couple of problems with this meta-analysis. First, while the research typically looks at being bullied in a school context, children of neglecting or abusing parents are by definition victims of bullying. They are bullied by their parents – they experience repeated aggression from someone who has more power than they do. Also, I tend to think that their peers bullying them is likely the least of these kids’ worries, if they are being abused at home by their parents. Another problem is that there was an effect of age – older children (12 and up) reported a less warm relationship with their parents (regardless of being bullied or not). But the authors did not check the effect of age on being bullied. So if there is an effect of age, it’s possible that this correlation is driven by age. Personally, I find it hard to believe that the incidence rate of bullying in the 4-7 years age group is as high as the incidence rate of bullying in the 12+ age group. Also, from my experience working with children, age is almost always a factor, and it should never be ignored in a developmental study. So until I see a non-correlation between the rate of bullying and age, I’m not quite convinced of the results.

By the way, the authors themselves note that most of the studies in their sample were cross-sectional (that is, they took a “snap-shot” in time rather than followed development over time) and that this “does not allow to differentiate cause and effect.” (pp. 13). This limitation does not prevent the authors from suggesting that “intervention programs against bullying should extend their focus beyond schools to include families…”. Interesting approach.

What It Means

I think all children would benefit in many areas of life from having warm, affectionate parents with whom they have a good relationship characterized by good communication, and who do not neglect and abuse them. I can’t imagine what I would do if I find out one of my kids is being bullied, but I would probably think this is somehow my fault. This study is not helping on that front. That said, there is an ongoing debate between researchers who think that parents don’t matter at all to development and researchers who think that parents do matter. If you look at this study from that lens, you can see it sitting squarely in the latter camp, bolstering the “weapons” (read: evidence). But that’s a topic for another post.

[*] Actually, it hasn’t been published yet – it’s “in press” which means it has been accepted for publication but not printed yet – academic world is crazy sometimes

Monkey See, Monkey Help

Photo Credit: CopyrightFreePhotos.HQ101.com
Photo Credit: CopyrightFreePhotos.HQ101.com

I love it when my kids play together. Typically, one of them starts something (say, run around the room in circles). The other one would join in, making it a party. Monkeys see and monkeys do, and my little monkeys love to mimic each other (and us, but that’s a different story). Kids and even babies mimic other kids and adults (as I’m sure many parents notice) – it’s how they learn and practice their skills. Our mimicry skills are so advanced, that babies, after watching an adult trying but not succeeding to do something, would actually mimic the intended action rather than the action they actually witnessed. If that’s not cool, I don’t know what is.

Researchers have long been interested in mimicry in children – especially infants – but they mostly investigated how infants mimic others’ actions. A new study that’s just been published looked at the effects that being mimicked has on infants.

What They Did

In a brilliant twist on regular mimicking studies, Malinda Carpenter and her colleagues randomly assigned babies (18-month-olds) to a mimicked and a non-mimicked group. In the mimicked group, the experimenter spent a few minutes following the baby around and mimicking their actions (stretching, sitting, running around, etc.). In the non-mimicked group (the control group) the experimenter spent the same amount of time not mimicking the babies. That is, for every action the baby did, the experimenter did a different action (sitting when the baby stood up, stretching up when the baby bended to pick something up, etc.). So the difference between the groups was only whether they were mimicked or not, with the experimenter-baby interaction carefully controlled (I love it when researchers carefully control other variables. It makes me happy).

After the “set-up” stage, they started the test phase. The experimenter (either the same one who mimicked the kids or a different one) “accidentally dropped” some sticks, and the researchers recorded whether the babies helped her gather her sticks back into the box (I wrote about a similar procedure here). Then she took the box to a cupboard but couldn’t open the cupboard door since her hands were full. The researchers recorded whether the babies helped her open the door.

What They Found

Interestingly, they found that babies that were mimicked were significantly more likely to help both the experimenter who mimicked them and the experimenter who didn’t mimic them. In other words, babies who were mimicked showed more pro-social behaviour and were generally more helpful. This experiment, by the way, is a replication of an experiment that found similar results with adults.

What It Means

First, this sounds like a fantastic way to get your toddler to cooperate! Just mimic them a bit before you ask them to do something. I’m definitely trying this with my own little rebellious devil (also known as my 2-year-old daughter). Another interesting implication is that this puts our natural tendency to mimic other people in a whole new light. If this exists in babies, there must be some innate roots, which means that we are wired to respond more helpfully to people (or creatures) who we think of as similar to us – who behave like us. Definitely food for thought.

Sharing is Caring

Adam and Naomi Sharing a Pear

Have you ever tried to get a toddler to share? Do you think it’s an impossible mission? Researchers at the University of Pittsburgh showed that it’s actually pretty easy.


Sharing behaviour is thought to be a part of “human lore”. Whether it is biologically encoded or just learned from being a part of human society, sharing is a behaviour that has helped the human race thrive.

But when do we begin to share? And what would compel us to share something?

Celia Brownell and her students used sharing tasks to measure toddlers (18- and 24-month-olds, which are pretty little). In these tasks, the experimenter first gave an equal amount of toys to the participating child and another experimenter who was playing the role of “play mate”. The experimenter then took all the toys back and gave all of them to the child. The “play mate” then indicated that she would like the child to share by giving subtle (sighing, looking sad) and not so subtle cues (reaching unsuccessfully for the toys, and eventually asking for some toys). In addition to the sharing tasks, they also tested children’s understanding of ownership (for instance, being able to identify mommy’s shoes and the child’s shoes as such), and got parental reports of the child’s self-understanding (things like using the word “me”) and language (which not enough studies measure!).

What Did They Find?

They found that almost all (96%) 24-month-olds shared at least once during those sharing tasks. In contrast, only 65% of the 18-month-olds shared at least once. So, about a third of the year-and-a-half old kids never shared the toys they were playing with or the snack they were given. The 18-month-olds seem to be either confused about what the “play mate” was doing, or they were just oblivious.

Another neat finding was that understanding ownership was related to sharing behaviour over and above age. So, regardless of age, children who better understood ownership shared more. What’s interesting is that it looks like it has to do with understanding social norms. The thing about ownership (a fascinating topic all by itself) is that there is nothing in the shoes that inherently marks them as belonging to mommy. So, in order to know that these are mommy’s shoes there is at least some kind of learning of links between objects and people. The authors suggest that both of these things, understanding ownership and sharing, may be driven by some kind of understanding of social norms and values, such as understanding that objects have value. However, it seems to me that the driving force might be just paying attention to the world around them and particularly to the people around them.

Can We Help Children Share?

Is there a way to promote sharing behaviour? One of the things about this study that differentiate it from previous studies on the topic is that the “sacrifice” of sharing wasn’t big. These were not toys that the children were particularly attached to, nor were they expected to share all of the toys – just some of them. I think these are interesting points. If the child can have an alternative or doesn’t have to share everything, it might be easier for them. I know for my kids, sharing ice cream is a lot harder than sharing chicken, for instance. And my kids are probably abnormal sharers – they are really good about sharing with each other (see picture above). With other kids, well, that’s a different story.

Were your kids good at sharing when they were two? Do you remember a turning point? Was it better with older/younger siblings? Please share your sharing stories! 🙂

Baby Sign Language: What is it good for?

Photo Credit: Athensparents.com
Photo Credit: Athensparents.com

Baby sign language is very popular these days. There are classes and online resources and it’s all based on the premise that signing with your baby introduces a host of benefits from better communication to long-lasting language advantage. A very recent study done by a group of researchers from Hertfordshire University put the premise to the test, and examined the effects of baby sign language on language development.

What they did

The authors recruited forty 8-month-old infants and their mothers, and randomly assigned each mother-infant dyad to one of four groups: a) British Sign Language training (for mothers); b) symbolic gesturing system (gestures adapted from baby-signing courses) training; c) “verbal training” (the mothers got the instructions to use the same words as the mothers in the other two groups, but there was no signing information); and d) no intervention at all. The design is beautiful. The researchers even made sure that the same words were used in all the “treatment” groups, and they assigned the same number of female and male infants (5 and 5) to each group, to control for the known gender effects. I particularly like the fact that they had not one, but two control groups (verbal training and no intervention). They followed up on the kids until the kids were 20 months old, and called the mothers every two weeks to do a phone interview (and probably mostly to remind them to use the signs).

What they found

The authors report that there was no effect at all of the intervention. The authors write: “The overall language development of all infants was similar regardless of the intervention that they experienced.” (pp. 579). Infants in the intervention groups acquired the target words a little earlier than the children in the no-intervention group, but that seems to be the extent of the impact of treatment. The authors conclude that there is no benefit to encouraging baby signing, at least when it comes to language development.


Here is my problem with this beautifully designed study: they had 40 infants total in their sample. That’s a very small sample size. In general, effects in child development tend to be small – there are a lot of factors in play, and no one thing determines something as complex as a child’s language skills. From a statistics point of view, the smaller the effect, the larger the sample you need to see it in the data. I ran the math, and their chances of detecting a small effect were 12%. In other words, there very well may be a small effect of using sign language with babies, but that in this study the sample was not big enough to detect it. Now, it’s true that this probably means that there is no huge benefit to signing from a language point of view. But the authors make it sound like there is no point at all: in talking about mothers who sign up for baby signing classes and such they say, “the efforts of these mothers may be unnecessary.” (pp. 586).

My two cents

I personally think there is a huge difference for the mother and for the mother-baby communication when using signs. I didn’t use signs with my son until he started daycare. When he started daycare (he was 9 months old and did half-days for a couple of months) he started signing because he learned it from the daycare workers. They taught me some of the signs, and it made the communication so much easier. He could say what he wanted – not everything he wanted, obviously – and I could see it was making him feel “empowered”. Not being able to communicate, by the way, is one of the main sources of frustration and tantrums in the second and third years of life (and why toddlers are so “terrible”). To me, preventing tantrums is most definitely a benefit of using signs with babies 🙂

Did you use signs with your baby? Did you find it helpful?