Are We Getting Smarter?

I have a book somewhere called Are We Getting Smarter?. It's written by James R Flynn, the man for whom the Flynn effect is named. For those of you who haven't heard of it before, essentially, every decade the average IQ increases. It's estimated that using an IQ test normed in 1997, the average IQ in 1932 would have been 80 (it should be 100).

Flynn's argument is that this change does not reflect actual intelligence. Instead, it reflects changes in testability. Essentially, the increased exposure to tests, due to higher education rates, higher rates of testing in education, and so forth, makes people better at taking tests, and this increases their IQ.

This is certainly possible. But I doubt it accounts for all of the increase. There are a lot of reasons why we should actually be getting smarter, and not just better at taking tests.

First, nutrition. Severe malnutrition in infancy can lower a child's IQ by around 20 points compared to better fed children. In regions where many children are malnourished, a significant correlation between height and IQ is generally found, because both are reduced by malnutrition.

There's an increase in the rates of obesity and obesity-related diseases throughout most developed countries. This is a concern, certainly, but the bright side of this change has been a decline in the rate of severe malnutrition in all age groups, including children. This is also shown by the historical increase in average height in these countries. Further, we've also seen the discovery of vitamins in 1912 and the first vitamin supplements in the 1930s.

In addition, nutritional status for infants and pregnant women has been subject to particular changes. Like all adults, pregnant women have had an increase in overall nutrition. However, they have also been marketed far more nutritional supplements than the general population, and are more likely to take these supplements. Birth control has also improved the health and nutritional status of mothers. Larger families cost more to feed, and repeated pregnancies put more strain on the mother's body - especially if she's also breastfeeding. With birth control, women have more control over their rate of birth, and typically choose to have a small number of children who are well-spaced apart.

And speaking of breastfeeding, the ratio of bottle to breastfeeding has gone through two distinct transitions. Most of us today are taught that 'breast is best', but when formula was first invented, this was not necessarily the case. A malnourished mother will generally produce poorer-quality breastmilk, to the point where if she has access to clean drinking water and enough quality infant formula, her baby could very well be more healthy if formula fed. (In modern times, unfortunately, many malnourished mothers lack access to safe water and/or can't afford to buy enough formula to actually meet their child's needs. If the formula is watered down to make it last, or if the water used to mix the formula contains pathogens, breastfeeding is definitely better regardless of maternal nutritional status. However, due to the lack of birth control in that time period, many mothers from otherwise affluent backgrounds were malnourished purely because of back-to-back pregnancies.)

By the 1970s, however, maternal nutrition had improved substantially. It was around this time that the shift back to breastfeeding began, in part spurred on by evidence that breastfed infants appeared to be doing better than formula fed infants. Soon after, the first studies linking breastfeeding to higher IQ were performed.

Lastly, we've seen the adoption of public vaccination programs. The intended impact, of course, was to reduce the rate of serious complications from viral illnesses, such as congenital rubella syndrome and measles encephalitis (both of which can cause severe cognitive disability). Those complications are rare even when infection rates are high, and therefore would have only a minimal impact on average IQ. But illnesses also interact with malnutrition. Fighting illness takes resources, and a child who is frequently sick will need to eat more when healthy to compensate for the work of fighting off infections. A child who is both malnourished and frequently sick will be in a worse nutritional state than a child with the same diet who has been vaccinated for those illnesses.

So changes in infant and childhood nutrition and health certainly can account for some increase in IQ in the past hundred years. But this isn't the only factor that we've changed.

From ancient times, lead has been used to make many different things, such as pipes for drinking water. The Romans used lead pipes despite at least some awareness of the danger of lead poisoning. Medieval Europeans, on the other hand, seem to have forgotten that there were any dangers to lead, and this continued into the industrial and modern period, when the uses of lead extended from pipes to include paint, gasoline, and other things.

The clinical symptoms of acute lead poisoning are severe and obvious, but such poisoning has always been fairly rare. However, chronic low-level lead exposure in the first five years of life has been shown to lower IQ slightly in children without any clinical symptoms of lead poisoning. Such exposure would have been nearly ubiquitous before we knew the dangers of lead, and has been declining steadily since we removed lead from gasoline and paint and began gradually removing existing lead sources from our lives.

And lead is not the only environmental toxin we have reduced our exposure to, though it's the best documented. While there are probably some new toxins in our environment that we don't yet know the risks of, overall, we have gotten much more careful about what we have in our food, drinking water and the air we breathe - especially for young children. Though we don't know the impact of many of these other toxins on IQ, it's likely that at least some of them can decrease IQ in children.

Lastly, there are also nonbiological environmental effects on IQ. During the first 2 years, the brain is actually pruning unneeded neurons to make room for the ones we will need. And one big determination of whether a neuron makes the cut is how it's being used - for example, a 6 month old baby can distinguish all the possible phonemes in all human language, but by 9 months, babies can only distinguish phonemes that are important in the languages they've heard regularly spoken around them. (For example, a 9 month old exposed to only Japanese will have lost the 'l' and 'r' distinction.)

This becomes particularly crucial when we consider the most disadvantaged children in society. At the beginning of the last century, if a child was orphaned or their parents couldn't care for them, society's answer was to put them in an institutional setting. A child who spends the first few years of life institutionalized will frequently end up with an IQ in the borderline to mild cognitive disability range, as well as suffering a wide range of behavioural and emotional problems. Fortunately, with greater awareness of the impact of orphanages on child development, most developed countries have eliminated or greatly reduced their use - replacing them with foster care, which, while still problematic emotionally, does not have a noticeable effect on the child's IQ score.

But it's not just orphanages that can result in pruning important neurons because of insufficient stimulation. Among children living in family environments, children who are victims of parental neglect typically show a decrease in IQ compared to adequately cared for children. The most dramatic examples are children like Genie, who spent the first 13 years of her life in a single room, chained to a potty chair for most of the time. Although it's uncertain whether Genie's IQ was normal to begin with, her early pre-isolation development was definitely not consistent with the severe cognitive and language impairments she showed in her teens and adulthood.

Of course, cases like Genie are extremely rare, but many more children are exposed to subtle neglect. For example, a parent who regularly leaves her baby to be babysat by a five year old sibling not only places the physical safety of both children at risk - this also results in the baby being exposed to less adult conversation and less competent scaffolding of early interaction and play. Even a parent who is suffering from serious depression tends to interact less with their infant, resulting in poorer language and social skills.

The good news is that exposure to child maltreatment is also decreasing. It used to be that children were not apprehended at all, even for the most severe abuse - only children who were orphaned or willingly relinquished wound up in state care. Since then, more and more children are being removed against their parent's will, including neglected children like the hypothetical five year old babysitter and infant sibling described above.

Even when children are not removed, their care is improving. Psychiatric treatments and parenting skills programs are more readily available and have become more effective. For example, before the invention of antidepressants, the only treatments for depression were hospitalization or expensive psychotherapy, neither of which were as effective. Several decades later, CBT was also invented, and has since become the front-line psychotherapy for depression. Both antidepressants and CBT are as effective in treating depressed parents as they are in treating anyone else, and are certainly reducing the rate of infants exposed to chronic parental depression. Parent-specific programs, such as parental sensitivity training, have also increased tremendously.

In addition, we have also seen an increase in programs aimed specifically at children. Head Start, a program that provides education and support to toddlers and preschoolers from low income families, was first implemented in the 60s. Participation in Head Start appears to improve cognitive ability in children. The same effect may also be seen among low-income children attending preschools in general - and certainly preschool attendance has increased tremendously.

Parenting Impact on Autistic Kids: You Can't Have Your Cake and Eat It Too

In the 1960s, autism (and childhood schizophrenia, which included many kids who'd now be diagnosed with autism) was thought to be caused by bad mothers. The theory referred to 'refrigerator mothers' - mothers so cold and distant that the child turned to autism as a coping strategy.

Now, of course, we know this is nonsense, and very hurtful to the mothers who were so unjustly blamed. Parents of autistic kids don't consistently differ from parents of non-autistic kids in their parenting skills. But many people in the autism community* go too far in the opposite direction - denying any impact of parents on their autistic kids.

What they don't seem to realize is that if parenting styles don't affect autistic kids, then a lot of autism therapies would also be useless, because these therapies involve deliberately and systematically doing things that some parents do on their own.

The easiest example is relational therapies such as DIR and Floortime. The interactional style that the therapists take in these therapies is pretty much the same as the parenting dimension known as 'parental sensitivity' - a very well studied parenting dimension that has a lot of important implications for child development in both typical and disabled children. Parents high in parental sensitivity tend to have children who are more securely attached, have fewer behaviour problems, have better social-cognitive skills, and even have slightly better language skills (especially if they have a disability affecting language development, such as deafness).

Based on this, we would predict that an intervention mimicking sensitive parenting behaviour should reduce behaviour problems, improve social skills, and improve language development, as well as improving attachment security. At least two of those effects has been documented as a result of relational therapies, with this study, this study, this study and this study all finding improvements in social skills and this study finding improvements in expressive language in autistic children receiving relational therapies. But in order for this treatment to work, autistic kids must also be affected by naturally-occurring differences in parental sensitivity (such as differences due to the parent's own attachment style or marital conflict).

ABA is less easily equated to parenting styles, because there are two distinct aspects to ABA - direct teaching and prompting of skills, and consistent rewards and punishments to modify behaviour. In parenting styles research, those two components split up into separate domains of parenting behaviour.

The impact of consistent rewards and punishments has been very extensively studied under the dimension of consistent discipline. Children who get consistent discipline tend to show lower behavior problems and better attention and impulse control. So it stands to reason that ABA, which includes consistent discipline, would reduce behaviour problems, and the research supports this. But similarly, naturally occurring variations in how consistently parents discipline their children (such as differences due to parental depression) must also affect autistic children's risk of behaviour problems.

Parental teaching has been studied far less than consistent discipline. However, parental direct teaching is associated with improved emergent literacy skills, mathematics skills and earlier toilet training (most parents directly teach toilet training, but the parents who start earlier tend to have kids who are fully toilet trained earlier). So, at the very least, this suggests that ABA's direct teaching should improve academic skills and self-care skills. This study and many others have found that ABA improves self-care, but I couldn't find any data on ABA's impact on academic skills. Once again, if ABA can directly teach skills to autistic kids, individual differences in parents' tendency to directly teach skills must also affect their kids.

Almost all of the practices commonly used in autism therapy are also things that a subset of parents do on their own. So it's intellectually dishonest to simultaneously claim that these therapies can affect autistic kids' development and at the same time insist that naturally occurring differences in their parents' behaviour can't also affect their children. And if you claim those treatments can cure autism (a claim that isn't supported by the data, by the way), then parents who do the same things spontaneously should logically also be able to cure autism (or prevent it - a really early cure is indistinguishable from prevention).

If parents can't cause autism, they also can't cure it. And neither can a therapist who only does things that many parents do anyway.

* Note - I'm using 'autism community' to refer to the community of mostly parents and professionals, while 'autistic community' refers to the community of mostly autistic adults.