Can Social Interventions Drastically Raise IQ?

Russell T. Warne

Jun 16, 2025

The good news is, raising a smarter child is easier than you think. It doesn’t require making an investment in expensive equipment of high-priced tutors. Nor do you have to devote every waking minute to demanding academic drills. There are easy (and I do mean easy) yet highly effective strategies that can vastly improve your child’s brain power. It’s as simple as playing the right games with your child, putting the right food on your child’s plate, maintaining a brain-enhancing environment in your home, and last but not least, giving your child lots of love. (Perlmutter & Colman, 2006, p. 3)

Authors of self-help books, like the book I quoted above, have no shortage of suggestions for how to increase intelligence. Blogs, parenting websites, and social media also have tips for raising IQ, usually in children. Scientists who have studied the issue, though, are usually more cautious, and the promises of raising a child’s IQ by 30 points (as in the book by Perlmutter & Colman, 2006) are not realistic. In this chapter, I’ll discuss the scientific evidence about social interventions to raise intelligence.

Social Interventions

A social intervention is a treatment or program to raise intelligence that is not medical or biological in its basis. Unlike social interventions, the methods of raising IQ that I discussed in Chapter 12 are all biologically based. They raise intelligence by improving brain health (i.e., treating iodine deficiency) or preventing brain damage (i.e., treating PKU or preventing lead poisoning). Social interventions, however, improve intelligence by helping a person’s psychological functioning or learning. They do not create major changes in the biology of the brain, but they do change how people think and reason.

In this book, I have already discussed one social intervention: education. Strong evidence indicates that keeping people in school longer results in higher IQ (Ceci, 1991; Ritchie & Tucker-Drob, 2018). Education has been a wildly successful social intervention to raise IQ, and it is likely to be the cause for some of the IQ gains seen in the Flynn effect (see Chapter 14). Another social intervention is adoption, which raises IQ by approximately 4–5 points (Jensen, 1998; Kendler et al., 2015). Therefore, it is reasonable to expect other social interventions to also increase IQ.

I’m Just a Poor Boy. Nobody Loves Me: Consequences of Severe Neglect

It is known that severe deprivation lowers IQ in humans. An early study of this topic was conducted in Iowa on children who lived in cramped conditions in a state orphanage with highly regimented and socially isolated lives. The focus of the few adults operating the orphanage was on meeting the children’s basic needs of food, shelter, and clothing. One-on-one interaction and care were rare, and there were few toys available. While these conditions are deplorable, they were typical of orphanages of the 1930s in the United States (Skeels, 1966). Regardless of initial IQ when they were admitted to the orphanage, prolonged time in the orphanage tended to result in an IQ score below 80 (Skeels, Updegraff, Wellman, & Williams, 1938, p. 42).

Yet, when children in this institution were transferred to a different environment with more social interaction, their IQ scores increased – often by a large amount. In one group of 13 children, IQ increased an average of 27.5 points in 18.9 months after transfer to a different state facility with more social interactions. Twelve similar children who stayed in the unfavorable conditions for an average of 26.5 months had IQ score declines averaging 26.2 points (Skeels, 1966, pp. 10, 13). In later follow-ups, 11 of the 13 children placed in a more favorable institution were adopted into homes, and 21⁄2 years later had an average IQ of 101.4, and the average of all 13 was 95.9 points – which is in the range of normal intelligence. The 12 children who stayed in the unfavorable institution had an average IQ of 66 at an average age of 6.9 years, and only three had an IQ score above 80 (Skeels, 1966, pp. 21–23).

Two decades later, Skeels tracked down the 25 children, and though he did not administer any intelligence tests, the differences between the two groups were apparent. All 13 of the children who spent time in the more favorable institution were able to live normal lives as adults, while 5 of the 12 people who stayed in the worse environment remained institutionalized. Only 1 of the 7 who lived outside an institution had a job that was not menial (Skeels, 1966, p. 33). The educational differences were stark, with the group that lived in more favorable conditions completing over seven more years of education, on average (Skeels, 1966, p. 37). Clearly, the early environmental differences had a long-lasting impact on these individuals.

While this study has a small sample size of 25, similar research has replicated these results many times. Across 42 studies totaling 3,888 individuals in 19 countries, the average IQ of children growing up in an orphanage was 84, while the average IQ of similar children living in foster homes was 104 (van IJzendoorn, Luijk, & Juffer, 2008). These studies show that prolonged exposure to an unfavorable environment in childhood probably has a long-term detrimental impact on a person’s intelligence.

These studies do not apply to children in the United States or other industrialized countries any more. Wealthy countries have eliminated overcrowding in orphanages and modern facilities, and an increased use of foster homes means that children whose birth parent(s) cannot care for them have a much more positive environment than what was common two or three generations ago for such children.

It is not entirely clear what aspect(s) of orphanages depressed IQ scores. Skeels (1966) suggested that it might be the lack of “nurturance and cognitive stimulation ... love and affection and normal life experiences” (p. 56). Physical health conditions and a lack of a family structure may also be important. Because no one knows why orphanage living depresses IQ, it is unclear how these studies apply to children who are subjected to long-term abuse and neglect while living with family members. This latter group is much larger in industrialized countries than the orphanage population, but they are hard to study. (Most people who are abusing a child do not volunteer for scientific studies about the effects of that abuse – for obvious reasons.) Based on the information from adoption studies and orphanage studies, it seems likely that putting children who are abused or mildly neglected by their parents into a more favorable environment could boost IQ, but it is not clear by how much.

Preschool

It is even less clear what more typical levels of poverty do to individuals’ IQ scores. Many children live in poverty, but not in environments that are neglectful or disadvantaging enough for the authorities to remove them from the care of their family. However, many of these children experience one intervention that is designed to increase their cognitive abilities: preschool.

Preschool is hugely popular, with 65.9% of 4-year-olds and 41.6% of 3-year-olds in the United States attending some form of preschool in 2016 (National Center for Educational Statistics, 2017, Table 202.10). Enrollment, though, is uneven, with children from wealthier families more likely to attend preschool (Tucker-Drob, 2012). Because education is known to increase IQ, it seems reasonable that preschool can be a social intervention that could raise intelligence. Early studies on the topic were promising. The most famous were the Perry Preschool Project, the Carolina Abecedarian Project, and the Milwaukee Project.

The Milwaukee Project. Started in 1966, the Milwaukee Project had a sample size of 48 African Americans. A total of 20 infants in an experimental group and 20 infants in a control group were considered “at risk” for an intellectual disability because of household poverty and having a mother with an IQ below 75. The remaining 8 were “low risk” because their mothers had IQ scores of 100 or above. The 20 children in the experimental group experienced one of the most intensive social science intervention programs ever devised. The mothers received home visits for 3–5 hours per week for the first 18 months in order to be trained in child care, hygiene, nutrition, financial management, and other parenting and household skills. Every day until the age of 6 (when the 20 children in the experimental group entered the first grade), the children spent time in a high-quality preschool. The child-to-caregiver ratio at this preschool started at 1:1 and gradually increased to 3:1 as the children aged. The experiences the children had in the preschool were numerous:

They [the experiences] include more ways that might conceivably promote cognitive development than a team of child psychologists could think up given a month with nothing else to do. Just about every form of didactic stimulation ever suggested by child development experts ... seems to have been scheduled. (Jensen, 1989, p. 244)

None of the children in the other two groups received any intervention, though they were given various tests at the same ages as the children in the experimental group.

At age 6, children in the experimental group outscored children in the control group by 21–32 IQ points (Jensen, 1989, p. 248). The children in the experimental group also outscored their siblings by 22.5 points (Jensen, 1989, p. 247), which indicates that the preschool intervention was probably an effective component of the Milwaukee Project because siblings would have also experienced the benefits from the home visits and any changes in parental behavior. By age 10, the experimental group IQ advantage had declined to 18 points. At age 14, there was “only” a 10-point difference between groups.

Academic performance also showed a similar decline for the experimental group. At the end of first grade, the children scored at the 49th percentile (compared to the 30th percentile for children in the control group) for reading, which is almost exactly equal to the average of the 50th percentile. However, by the end of the fourth grade, the experimental group scored at the 19th percentile (compared to the 9th percentile for the control group) in reading. Similar declines were observed in math (from the 34th to 10th percentile for the experimental group in the same grades, compared to a decline from the 18th to 9th percentile for the control group at the same ages).

The score declines and the mismatch between IQ scores and academic performance for the experimental group suggest two conclusions. First, the benefits of the Milwaukee Project’s preschool program were not permanent. After they ended, children in the experimental group gradually lost the academic benefits they received in their early childhood. Second, the Milwaukee Project probably raised the IQs of the experimental group children, but did not raise their levels of g, as indicated by the severe underachievement in school (Jensen, 1989, 1991, 1998). Thus, the gains in the Milwaukee Project are likely because the staff at the preschool taught the children how to answer intelligence test problems – but not how to improve their general reasoning ability to situations outside the testing setting.

The Carolina Abecedarian Project. The Carolina Abecedarian Project started in 1972 when children were an average of 4.4 months old and continued until age 5. During this time the 57 children in the experimental group attended an academically focused day care for “8 hours a day, 5 days a week, 50 weeks a year” (Spitz, 1997, p. 72). The experimental group also received home visits, and parents were taught how to help their children in school (Protzko, 2017a). Almost all of the 111 participants in the study were African American, though their mothers’ IQ scores were higher than in the Milwaukee Project, with an average of 84 (Jensen, 1998, p. 342). At age 5, the experimental group had IQ scores that were 7.5 points higher (on average) than the average IQ score of the 54 members of the control group. This difference declined to 5 points by age 8, where it stayed through adolescence.

Like the Milwaukee Project, the Carolina Abecedarian Project has IQ gains that favor the group that experienced preschool, but some of these IQ score gains were lost over time. Unlike the Milwaukee Project, though, the Carolina Abecedarian Project’s IQ score gains also were accompanied by improved performance in school (Jensen, 1998; Neisser et al., 1996). This might indicate that these are real gains in g, though some people (e.g., N. Brody, 2008; Spitz, 1997) are still skeptical.

The Perry Preschool Project. Of the three early studies in the effectiveness of preschool, the Perry Preschool Project is the one that most resembles typical preschool programs. The Perry Preschool Project started in 1962 in Ypsilanti, Michigan, and has followed a total of 123 subjects through age 40. Beginning at age 3, and continuing until age 5, the 58 children in the experimental group spent 21⁄2 hours per weekday in a preschool for 30 weeks per year. The preschool had a student-to-teacher ratio of 6:1 and a curriculum focused on cognitive growth and social skills (Nisbett, 2009). Additionally, once per week, teachers visited the children’s home. All children had IQ scores between 70 and 85 and lived in families with low socioeconomic status.

At age 5, when the children entered kindergarten at their regular schools, the experimental group had an IQ of 95, and the 65 children in the control group had an IQ of 83. By the end of grade school, both groups had an IQ of 85 (Nisbett, 2009). However, the school performance of the experimental group was much higher than the school performance of the control group, which did not occur in the Milwaukee Project.

Discussion of the Early Preschool Studies. Advocates of preschool point to these early studies as evidence that they raise intelligence (e.g., Nisbett, 2009), but my summaries of them show that such an interpretation is incomplete. In all three studies, IQ gains diminished greatly after children left the preschool program and entered the regular school environment. This tendency for IQ gains to diminish over time after an intervention ends is called fadeout, and it is extremely common in interventions to raise intelligence (Protzko, 2015). Apparently, the only way to eliminate fadeout completely is for a treatment to continue indefinitely. This may explain why adoption and removing children from severely neglectful environments (like an overcrowded orphanage) are effective at producing a permanent increase in IQ: these interventions almost always last until adulthood when the children leave their adoptive parents’ home and begin their own independent lives. However, even in adoption studies, the impact of the beneficial home environment is stronger for young children than for older adolescents (e.g., compare Scarr & Weinberg, 1976, and Weinberg, Scarr, & Waldman, 1992), indicating that a form of fadeout still occurs for the long-lasting, pervasive “treatment” of adoption.

It is also important to note that these early studies are much more intensive – and therefore expensive – than most preschool programs. A representative example of this is in teacher-to-student ratios. In the United States in 2016, there were 4.701 million preschoolers (National Center for Educational Statistics, 2017, Table 202.10) and 478,500 preschool teachers (Bureau of Labor Statistics, 2018). This means that the average student-to-teacher ratio is 9.8:1 – higher than the ratios in these early studies. Additionally, the educational curriculum of these preschool programs would most likely require much more teacher training than the typical preschool teacher currently has. As a result, these studies provide little evidence that typical preschools increase IQ. For that, it is necessary to turn to modern studies.

Modern Studies of Preschool. The best modern studies of the effects of preschool use a design called the randomized control trial (RCT), which randomly assigns subjects to experimental or control groups. Randomization balances out the groups in every way so that any remaining differences can only be due to the treatment that one group received and the other group did not.

RCTs of preschool are promising. Protzko and his colleagues (2013) found that the average impact of preschool across 16 RCT studies was 4 IQ points for typical preschools and 7 IQ points for preschools that include a language component. Unfortunately, these studies – and many other interventions – suffer from fadeout, and over time the gains are lost as children age (Protzko, 2015).

Moreover, recent studies indicate that preschool interventions produce smaller differences between preschoolers and non-preschoolers in the twenty-first century than they did in the early research on the topic (Duncan & Magnuson, 2013). While this may be surprising to readers, it may merely indicate that the home environment of non-preschoolers has improved, which means that there is less that modern preschool can do to improve a child’s outcomes. This is another reason why the findings of the Perry Preschool Project or the Carolina Abecedarian Project may be misleading for a typical, modern setting.

Two recent RCTs are worth discussing in detail. The first was an RCT commissioned by the US Congress to investigate the Head Start program (US Department of Health and Human Services, 2012). With a sample size of 4,667 children who were randomly admitted to or rejected from Head Start, this is the largest RCT ever conducted in preschool. The second was an RCT study of 2,990 children whose parents or guardians applied for them to attend the preschool program created by the state of Tennessee (Lipsey, Farran, & Durkin, 2018). Although neither study includes data from intelligence tests, both studies report scores from academic tests, which are reasonably good measures of g.

The findings of both studies are remarkably consistent. At the start of kindergarten, children who participated in preschool had higher scores on a variety of academic measures. However, most of these advantages were gone by the end of first grade. By the end of third grade, children who did not attend preschool were performing as well or better on almost every academic measure. Both of these studies showed that fadeout is not a phenomenon unique to IQ scores. Indeed, the Head Start study reported a variety of health, home, and social/emotional variables, and these all showed fadeout, too (US Department of Health and Human Services, 2012).

Does this mean that preschool is a waste of time and money? Not necessarily. The short-term gains in cognitive and academic variables are undeniable. Whether those gains are worth the expense is a value judgment that will depend on the social goals of parents, government personnel, and others. And there may be non-academic benefits to preschool. For example, if a child’s caregiver would prefer to join the workforce, then sending a child to preschool may improve caregiver happiness, contribute to the economy, and improve the family’s financial situation. Additionally, many preschool programs (especially those funded by government entities) also encourage immunization of children and provide vision and hearing screenings. Some preschool programs also provide regular nutritious meals for children. These are unequivocal benefits for a child, especially for children whose parents cannot afford these services. Preschool does not have to raise IQ to be a beneficial experience for children.

Additionally, it is possible that some long-term benefits of preschool do not manifest themselves until adolescence or adulthood. Follow-up studies of the Perry Preschool Project participants indicate that children who participated in preschool had higher rates of high school graduation, less criminal behavior, higher incomes in adulthood, higher rates of college attendance and home ownership, and lower rates of smoking (Conti, Heckman, & Pinto, 2016; Nisbett, 2009; Schweinhart & Weikart, 1993). Proponents of preschool call these positive impacts sleeper effects, because they are dormant for a long time and do not show themselves until many years after the intervention ends. Both the Carolina Abecedarian Project and the Perry Preschool Project provide evidence of sleeper effects in the children in their experimental groups. If these sleeper effects are real, then investing in high-quality preschool could provide society with major economic benefits as these preschoolers reach maturity.

Sleeper effects are plausible, and nobody has produced a study that disproves their existence. However, it is not clear how sleeper effects develop. (A young adult isn’t going to say to himself, “My friends want me to, but I won’t steal a car today because I went to preschool when I was 4 years old.”) Clearly, sleeper effects cannot be a direct consequence of improved school performance or intelligence because these fade out during the first few years after preschool ends. Theories based on improved social skills or emotional regulation are not promising because these improvements also fade out after preschool ends (Lipsey et al., 2018; US Department of Health and Human Services, 2012). Verifying the existence of sleeper effects and explaining their exact cause is a major challenge to preschool research in the coming decades (Duncan & Magnuson, 2013).

It is not promising that sleeper effects are based on early studies that do not resemble modern preschool programs. It might not be reasonable to expect sleeper effects to emerge from typical preschool programs. Moreover, all the preschool programs I have discussed in this chapter have been designed for children from low-income families. Expecting sleeper effects and long-term benefits of preschool for children from middle-class and wealthy families may not be justified (Woodhead, 1985). Indeed, it is possible that middle-class and wealthy children experience none of the cognitive benefits of preschool – even the short-term academic benefits.

An additional challenge is that any educational program – no matter how well designed – will appear ineffective when implemented poorly. Carefully controlled pilot studies of educational programs often show strong benefits. But when these are scaled up to encompass many classrooms and communities, there is less control on how staff members operate the program, and the effective component(s) may not be implemented well. This often causes programs to appear ineffective when implemented on a large scale (e.g., Cook et al., 2018) and may be why the Perry Preschool Project and other local, carefully supervised studies produce different results than the nationwide Head Start RCT or the statewide Tennessee RCT.

Other Social Interventions to Raise Intelligence

While there have been other social interventions to raise intelligence, most have been too sporadically studied to produce any firm conclusions. Evidence regarding social interventions to raise IQ has been slow to develop for a variety of reasons. One is that – apart from education – there is little consensus about what other interventions would produce a large, noticeable change in problem-solving abilities. As a result, it is not clear what sort of interventions might be worth implementing as an attempt to raise IQ. Additionally, social interventions often have many components, which can make it difficult to isolate the aspects of an intervention that might have a positive impact on intelligence. This is certainly true for preschool programs, adoption studies, and the negative aspects of orphanages.

However, one social intervention that has been studied quite a bit is the famous Mozart effect, which originated in a study in which college students who listened to a Mozart sonata performed better on a spatial reasoning task immediately afterwards (Rauscher, Shaw, & Ky, 1993). This study usually does not replicate (e.g., Pietschnig, Voracek, & Formann, 2010; Stough, Kerkin, Bates, & Mangan, 1994), and psychologists believe that the effect is not real. There is no evidence that Mozart’s music is special in any way or that playing it – or any genre of music – increases listeners’ intelligence. Unfortunately, one recent study showed that 59% of the general public and 55% of teachers believe that classical music increases children’s reasoning ability (Macdonald, Germine, Anderson, Christodoulou, & McGrath, 2017).

Conclusion

The evidence is unequivocal that children who spend a long period of time in a neglectful, deprived environment experience a lowered IQ and long-term negative effects. Removing children from an environment like this – whether through adoption or improving their living conditions – is a boon for their intelligence (and their quality of life, in general).

For children who live in poverty, preschool is, by far, the most studied social intervention to raise intelligence, and early studies were promising. Initial results of preschool are always strong, but as soon as the intervention ends, fadeout starts, and any gains are usually gone within a few years. Although benefits of preschool may accrue in adolescence or adulthood, it is unclear how this happens and whether these benefits occur in typical preschool programs.

Raising intelligence permanently is hard, and it seems that nothing short of an intensive, years-long intervention that includes academic, social, and health improvements throughout childhood and adolescence will permanently raise IQ. Psychologists do not know, at this time, how to use social interventions to improve the intelligence of children who live in middle- or upper-class homes in industrialized countries.

From Chapter 15 of "In the Know: Debunking 35 Myths About Human Intelligence" by Dr. Russell Warne (2020)

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