Parents Miss a Critical Window to Develop Their Children
Parents Miss a Critical Window to Develop Their Children’s Cognitive Ability and Personality
Many parents begin thinking seriously about their children’s development when school results become disappointing. By then, the child may be ten, twelve, or fifteen years old. The parents hire tutors, change schools, introduce stricter study schedules and demand better grades. These interventions may help, but they come after some of the most important years of development have already passed.
The greater opportunity occurs much earlier. It starts during pregnancy and continues through infancy, preschool and the first years of primary school. During this period, parents can protect the biological foundations of cognitive development, establish reading and learning habits, and encourage behaviours that later become part of the child’s personality.
This does not mean parents can manufacture a highly intelligent child or design a preferred personality. Both cognitive ability and personality are substantially influenced by heredity. Children are born with different natural capacities, temperaments, and developmental tendencies. Some learn quickly, while others need more repetition. Some are naturally outgoing, while others are reserved. Some remain focused for long periods, while others are easily distracted. Good parenting does not erase these differences.
However, heredity is not destiny. Genes influence a range of possible outcomes, but the conditions surrounding a child affect where within that range the child is likely to develop. Parents may not control the genetic potential their children inherit, but they have considerable influence over whether that potential is protected, neglected or damaged.
That is the opportunity many parents miss.
What heritability really means
Discussions about children’s development often fall into two opposing camps. One side argues that intelligence and personality are inherited and therefore parents can do very little. The other claims that any child can become anything with sufficient parental effort and the right training. Neither position reflects the evidence.
Research involving twins and adopted children consistently finds that cognitive ability is substantially heritable. One large study involving approximately 11,000 pairs of twins estimated the heritability of general cognitive ability at about 41% at age nine, 55% at age twelve, and 66% at age seventeen. Heritability increased as children grew older. This may happen partly because children increasingly select activities, friends and environments that fit their natural tendencies. A child with strong verbal ability may read more, seek intellectually demanding conversations and choose subjects that further develop that strength.
These percentages are population estimates. They do not mean that 41% of a particular child’s intelligence comes from genes while 59% comes from the environment. They describe how much of the observed variation among people in a particular population, at a particular time, is associated with genetic differences. The figure can change when living conditions, educational access, health, or nutrition change.
A trait can be highly heritable and still be affected by the environment. Height is strongly heritable, but severe childhood malnutrition can prevent a child from reaching their potential height. Cognitive ability works in a similar way. A child may inherit strong cognitive potential, but chronic malnutrition, untreated illness, exposure to toxins, poor sleep, inadequate stimulation or prolonged stress can prevent its full expression.
Personality is also partly heritable. Behavioural genetic studies commonly attribute a substantial share of differences in personality traits to genetic influences. A review of personality research reported that twin studies frequently place the genetic contribution at around half of the observed variation, although estimates differ by trait, age, population and method. Research on personality heritability makes one point clear: children do not arrive as blank slates.
Parents with two or more children see this without needing a scientific study. Children raised in the same home can be remarkably different. One may be cautious and compliant, while another is adventurous and argumentative. One may organise schoolwork without being reminded, while another repeatedly loses books and misses deadlines. The same parents, home and school do not produce identical people.
The remaining environmental influence is also not simply “parenting.” It includes illnesses, teachers, friendships, accidents, opportunities, birth order, classroom experiences, and events unique to each child. Parenting is only one part of the environmental contribution. It is nevertheless an important part because parents shape the child’s earliest and most persistent environment.
The first responsibility is to protect the brain
Parents often try to develop cognitive ability by buying educational toys, enrolling children in expensive schools or downloading learning applications. These measures are secondary. Before a brain can benefit fully from instruction, its physical development must be protected.
Cognitive development begins before birth. Maternal health, nutrition, exposure to alcohol and harmful substances, antenatal care, infection control and complications during pregnancy can affect the developing child. The first parenting decision is therefore not which preschool to choose. It is how seriously the family treats health before and during pregnancy.
The first 1,000 days, running from conception to roughly the child’s second birthday, are particularly important. The brain grows rapidly during this period. It needs adequate energy, protein and micronutrients. It also needs protection from disease, toxins, injury and prolonged deprivation.
Iron deficiency deserves particular attention. The World Health Organization warns that iron deficiency in children under two can have serious and potentially irreversible effects on brain development, learning and later school performance. Maternal iron deficiency during late pregnancy may also affect the child’s cognitive development. WHO guidance on iron deficiency supports early detection rather than waiting until poor concentration or delayed development becomes visible.
Iodine is also essential because it supports thyroid hormone production and neurological development. Severe deficiency during pregnancy and early childhood can cause lasting intellectual impairment. Folate and other nutrients matter as well. However, parents should not turn this into uncontrolled supplementation. Excessive doses can also be harmful. A qualified health professional should assess suspected deficiencies and recommend appropriate treatment.
Adequate nutrition does not mean purchasing fashionable supplements. It means providing regular, safe and varied meals containing nutrient-dense foods. Depending on local availability and medical advice, this normally includes protein sources, vegetables, fruits, legumes, whole grains and other foods that supply the nutrients needed for growth. UNICEF recommends that complementary foods introduced from around six months should be frequent, nutritionally dense and drawn from a variety of food groups. UNICEF’s early-childhood nutrition guidance also stresses responsive feeding and food hygiene.
Nutrition programmes in preschools and early-years centres exist for this reason. A hungry or malnourished child does not enter the classroom on equal terms with a well-nourished child. School feeding is not merely a welfare intervention. Where nutritional deprivation is common, it is part of a country’s human-capital strategy. A review of nutrition interventions found positive cognitive effects among undernourished preschool children, although results varied according to the intervention, children’s nutritional status and the outcomes measured. The review of nutritional interventions reinforces a basic principle: preventing deficiency is far better than attempting to repair its effects years later.
Health extends beyond food. Repeated infections, untreated hearing or eyesight problems, chronic respiratory conditions and poor dental health can interfere with sleep, attention, language acquisition and school participation. A child who cannot hear the teacher clearly may be labelled slow or inattentive. A child with poor eyesight may avoid reading. A child who sleeps badly may struggle with memory and self-control. Parents should not interpret every learning difficulty as laziness.
Routine health checks, immunisation, developmental monitoring and early treatment are investments in cognitive development. Parents should also protect children from lead and other neurotoxins, second-hand smoke, alcohol exposure, unsafe medicines and preventable head injuries. No cognitive-training programme can compensate fully for a brain repeatedly exposed to avoidable harm.
Responsive care develops the foundations of thought
A child’s brain is not developed by food alone. It also needs interaction. Talking, singing, playing, explaining and responding to a child’s signals create repeated opportunities for language, memory, attention and reasoning to develop.
UNICEF describes early childhood as a critical developmental window requiring health care, nutrition, safety, early learning and responsive caregiving. Responsive caregiving means noticing what the child is attending to, responding to questions, naming objects, encouraging exploration and providing comfort when the child is distressed. UNICEF’s early-childhood development guidance places these ordinary interactions at the centre of development.
Many parents underestimate the cognitive value of conversation because it looks too simple. Yet a child learns concepts by hearing words used in meaningful situations. When a parent explains why rain falls, compares the sizes of two containers or asks what might happen next in a story, the child is learning how to classify, predict, compare and infer.
Parents do not need to conduct formal lessons throughout the day. They need to make the child think. During shopping, a parent can ask the child to estimate the total cost or identify which item provides better value. During cooking, the child can measure quantities, follow a sequence and observe changes in temperature and texture. During travel, the parent can discuss distance, direction and landmarks. Household life is full of cognitive material when adults stop giving children every answer.
Play performs the same function. Building blocks develop spatial reasoning and planning. Sorting objects develops classification. Puzzles require analysis and persistence. Pretend play develops language, perspective-taking and imagination. Rule-based games teach children to hold instructions in mind, wait for their turn and manage disappointment.
The parent’s role is not to take control of the activity. When adults correct every move, children become dependent on instruction. Productive play allows the child to attempt, fail, adjust and try again. The learning occurs partly in the struggle.
Reading is one of the most accessible interventions
If parents can establish only one consistent intellectual habit at home, reading should be a leading candidate. Reading exposes children to vocabulary, sentence structures, knowledge and ideas that ordinary conversation may not provide. It also trains attention, comprehension and imagination.
The evidence is strongest for language and literacy outcomes. A recent meta-analysis covering 28 studies and more than 24,000 participants found a meaningful association between home-based shared book reading and children’s developmental outcomes, particularly spoken language and vocabulary. The researchers also warned that much of the evidence is correlational. Families that read frequently may differ from other families in education, resources and parental engagement. It is therefore wrong to attribute every observed difference to books alone. The shared-reading review nevertheless supports reading as a practical part of a developmentally rich home.
Intervention studies provide further support. Research on interactive shared reading shows that parents from different socioeconomic backgrounds can learn effective reading techniques. The value does not come merely from pronouncing every word while the child listens. It comes from interaction.
A parent should ask the child what is happening, why a character acted in a particular way, and what may happen next. The child can be asked to describe a picture, explain an unfamiliar word or connect the story to something experienced at home. After finishing, the child can retell the story in their own words. This develops retrieval, sequencing, interpretation and verbal expression.
The questions should match the child’s age. A three-year-old may identify colours, animals and actions. A six-year-old may explain motives and consequences. An older child may challenge the author’s argument, compare two characters or suggest a different ending.
Parents should read to children before children can read independently. After independent reading begins, the shared routine should not immediately stop. Parents can take turns reading, discuss separate books or ask the child to teach them something learned from a book. The aim is to move gradually from being read to, to reading with someone, and finally to reading voluntarily.
Access matters. Books should be visible and reachable rather than locked away for protection. Where buying books is difficult, families can use libraries, exchange books with other parents, print suitable public-domain material or use carefully selected digital texts. The number of expensive books in the home is less important than whether anyone opens and discusses them.
Parents must also model the behaviour. A child who is repeatedly told to read while every adult spends the evening scrolling through a telephone receives a contradictory message. Children pay more attention to the household’s actual habits than to its speeches.
Schooling itself develops cognitive ability
Parents sometimes treat cognitive ability as something fixed before the child enters school. That is incorrect. Education does more than transmit facts. Good teaching develops vocabulary, quantitative reasoning, knowledge, problem-solving strategies and the ability to work with increasingly abstract information.
Heiner Rindermann’s research has examined how parental education, instructional quality and broader educational conditions relate to children’s cognitive development. In research covering 19 samples across seven countries, Rindermann and Stephen Ceci found parental education to be more strongly associated with children’s cognitive ability than parental wealth. The study does not prove that parental education alone causes higher ability because educated parents also differ in genetic, linguistic and behavioural ways. It does, however, challenge the assumption that money is the main requirement. Rindermann and Ceci’s study points towards the value of educational behaviour within families.
Rindermann’s comparative work involving children in Germany and Vietnam also examined parenting and instruction alongside cognitive performance. The broader lesson is that cognitive development reflects a combination of inherited ability, educational exposure and the quality of intellectual demands placed on children. Parents should therefore judge a school by more than buildings, uniforms and examinations. They should examine what happens in the classroom.
Do teachers explain concepts or rely on copying? Do children solve unfamiliar problems? Are they required to read and write extensively? Do teachers give useful feedback? Does the school identify learning difficulties early? Is instructional time protected? A prestigious name cannot compensate for weak teaching.
Regular attendance also matters. Parents sometimes tolerate unnecessary absenteeism in early grades because the work appears easy. Yet missed instruction accumulates. Vocabulary, number concepts, and reading skills are cumulative. A child who misses a foundation may struggle with later material that assumes the foundation is secure.
Cognitive training can help, but it is not main solution
When parents realise that an opportunity may have been missed, they often look for a programme that promises to raise intelligence quickly. This market contains legitimate interventions, exaggerated claims and expensive nonsense.
Cognitive training generally produces the strongest improvements in the skill being practised and in closely related tasks. A child trained intensively on working-memory exercises may improve on similar working-memory tasks. That does not automatically mean the child will show a large, permanent increase in general cognitive ability or suddenly perform better across every school subject.
Germany has contributed an important body of work in this area. Karl Josef Klauer developed programmes to train inductive reasoning in children. Inductive reasoning involves detecting similarities, differences, patterns and relationships and then drawing a general conclusion. It is central to many forms of learning.
A review by Klauer and Gary Phye examined 74 training experiments involving nearly 3,600 children. It reported benefits for inductive reasoning and evidence of improvement in academic learning. Their review of inductive-reasoning training suggests that structured strategy instruction can be useful when it teaches children how to approach classes of problems rather than merely rehearsing test items.
Klauer’s programme is more thoughtful than giving children random “brain games.” Children learn to compare attributes, recognise relationships, identify categories and distinguish relevant from irrelevant information. Parents can support similar thinking at home by asking children to explain how objects belong together, identify what does not fit, complete patterns and justify conclusions.
The important word is “explain.” Guessing the correct answer is not enough. A child should describe the rule used to reach it. This develops awareness of reasoning strategies and helps parents detect whether the child understands or is simply responding through trial and error.
Cognitive training should be targeted. If an assessment shows weakness in a specific area, such as working memory, phonological processing, attention control or inductive reasoning, a qualified professional can recommend an appropriate intervention. Training should have clear goals, credible evidence and progress measures. Parents should ask whether improvement transfers beyond the exercises and whether it remains after training ends.
A commercial application that makes a child faster at the application may be entertaining, but speed inside a game is not proof of general intellectual growth. Claims of dramatic IQ increases should be treated with suspicion.
Personality is influenced through repeated behaviour
Parents cannot simply choose a personality for their child. A naturally introverted child should not be treated as defective, and an energetic child should not be punished merely for having a high activity level. The aim is not to replace temperament. It is to help the child develop useful habits and regulate less helpful tendencies.
Personality becomes more stable with age. In childhood, however, behaviour remains comparatively flexible. A meta-analysis of personality development found that stability is lower in childhood and increases towards adulthood. Both genetic and environmental processes contribute to that increasing stability. Research on personality development therefore supports early attention without implying that parents possess total control.
Parents influence personality mainly through repeated expectations, modelling, reinforcement and opportunities to practise behaviour. A child does not become conscientious because a parent delivers a lecture on responsibility. Conscientiousness grows through routines: putting toys away, completing small duties, arriving on time, keeping promises and finishing tasks before moving to entertainment.
Responsibilities should increase with age. Young children can return objects to their proper place. Older children can prepare school materials, manage small amounts of money, follow a timetable and contribute to household work. Parents who do everything for their children may believe they are being loving, but they can unintentionally prevent the development of independence and responsibility.
Emotional stability develops partly through learning how to handle discomfort. Parents should comfort distressed children, but comfort should not become the removal of every challenge. A child must gradually learn to tolerate waiting, losing, making mistakes, receiving correction, and attempting difficult tasks. Shielding children from all frustration leaves them poorly prepared for school, work and relationships.
Agreeableness is supported when children learn empathy, courtesy, cooperation and respect for boundaries. Parents can ask how another person may have felt, require sincere apologies and insist that children repair harm where possible. However, agreeableness should not be confused with helpless compliance. Children also need to express disagreement respectfully and protect themselves from exploitation.
Openness can be encouraged through books, music, art, nature, cultural experiences, new foods, unfamiliar ideas and questions without predetermined answers. A child does not need expensive international travel. A visit to a market, workshop, museum, farm, court, factory or place of worship can broaden understanding when an adult explains what is happening.
Social confidence develops through practice. Reserved children can be given manageable opportunities to greet visitors, ask for an item in a shop, explain their work or participate in a small group. Forcing them into overwhelming situations may increase anxiety. Gradual exposure is more sensible than humiliation.
Recent longitudinal research has also found that affectionate parenting in childhood predicts some personality differences in early adulthood, including greater openness, conscientiousness and agreeableness, even after several alternative explanations were considered. These effects were not enormous, and the researchers did not claim that parenting overrides genetics. The 2025 study on parenting and later personality supports a more measured conclusion: warm, consistent parenting can leave a lasting behavioural mark.
Discipline must teach self-regulation
The purpose of discipline is not to make children fear their parents. It is to help them regulate themselves when the parent is absent.
Rules should be few, clear and consistently applied. Consequences should be related to the behaviour and proportionate to its seriousness. Parents should explain what was wrong, what the child should do next time, and how any damage will be repaired. Anger without instruction may stop behaviour temporarily, but it teaches little.
Consistency matters because children learn patterns. If screaming sometimes secures a desired item, screaming is reinforced. If unfinished responsibilities are routinely completed by an adult, avoidance is rewarded. Parents sometimes create the behaviour they later complain about.
Praise should focus on specific conduct rather than exaggerated labels. “You kept working even when that problem was difficult” is more useful than “You are a genius.” The first reinforces persistence. The second can make the child afraid of tasks that may expose the limits of the label.
Children should also see adults regulate themselves. A parent who demands patience while shouting at every inconvenience is teaching impatience. A parent who admits an error, apologises and corrects it teaches more about character than a long speech about integrity.
What parents should do at each stage
During pregnancy, the priority is maternal health. Attend antenatal appointments, follow medical guidance, address nutritional deficiencies, avoid alcohol and harmful substances, and treat infections early. Families should regard the mother’s health as part of the child’s development rather than a private responsibility that she carries alone.
From birth to two years, priorities include appropriate feeding, immunisation, health monitoring, sleep, safety and responsive interaction. Talk to the baby, imitate sounds, sing, name objects and respond to attempts at communication. Watch developmental milestones without turning normal variation into panic. Seek professional advice when hearing, vision, movement, language or social development appears seriously delayed.
From ages two to five, language and self-regulation deserve sustained attention. Read daily, ask questions, encourage pretend play, provide simple puzzles and allow the child to help with real household activities. Establish sleep and meal routines. Teach waiting, taking turns, tidying up and completing simple tasks.
From ages six to nine, strengthen independent reading, number skills, curiosity and responsibility. Ask the child to explain schoolwork rather than merely show marks. Provide chores, monitor health and sleep, and communicate with teachers. If progress is unexpectedly weak, investigate possible learning, attention, hearing, visual or emotional difficulties early.
From ages ten onward, parents should gradually shift from controlling every decision to teaching judgement. Discuss ideas, current affairs, money, work and consequences. Encourage demanding reading, organised study, sport or physical activity and participation in responsibilities outside the immediate home. Assess the child’s aptitude, interests and personality before imposing subjects or careers.
At every stage, the goal is not maximum stimulation every hour. Children need rest, unstructured play and secure relationships. A home run like an examination camp may produce anxiety rather than healthy development.
Do not confuse opportunity with blame
The argument that parents matter can easily turn into unfair blame. Families differ in income, health, time, education, housing and access to services. A parent working long hours to keep food on the table does not have the same options as a parent with flexible employment, books, private health care and domestic support.
Children also experience developmental conditions that are not caused by poor parenting. Genetic disorders, disabilities, birth complications and mental-health conditions require professional support, not moral judgement. Even excellent parenting cannot guarantee high cognitive ability, exceptional school performance or a particular personality.
The correct message is not that every disappointing outcome is the parents’ fault. It is that parents should use the influence they actually possess while recognising its limits. The most powerful actions are often ordinary: protecting health, preventing nutritional deficiencies, ensuring adequate sleep, speaking with children, reading regularly, enforcing reasonable routines, modelling self-control, demanding age-appropriate responsibility and obtaining help early when something appears wrong.
Parents cannot rewrite the genes their children inherit. They can protect the developing brain, enrich the environment in which those genes operate and help useful behaviours become habits. They can also avoid preventable harm.
The tragedy is not that every child fails to become exceptionally intelligent or to possess an ideal personality. Such an outcome is neither realistic nor necessary. The tragedy is when a child’s available potential is reduced by malnutrition, untreated illness, intellectual neglect, chaotic parenting or years without books, conversation and meaningful challenge.
By the time examination results reveal the consequences, part of the opportunity may already have passed. The work of developing a child does not begin when school becomes difficult. It begins before birth, continues through the earliest years, and is built through thousands of small decisions long before anyone starts discussing careers.