The biological lens

The lens in brief

The biological perspective explains behaviour through the body: the brain and nervous system, hormones, genes, and the evolutionary history that shaped them. It uses methods such as brain imaging, hormone measures, and studies of twins and adopted children. A good biological account does not say "biology instead of environment". It asks how bodies and environments work together.

The Bobo doll study measured no biology at all. But two of its findings invite a biological question: why did boys show more physical aggression, and why did children differ so much from one another?

How this lens reads the study

Imitation is a biological capacity. Human children copy others with great accuracy, from very early in life. In a well-known comparison, Victoria Horner and Andrew Whiten (2005) showed young chimpanzees and three- and four-year-old children how to open a puzzle box using some steps that were clearly useless. The chimpanzees skipped the useless steps once they could see they did nothing. The children kept copying them. Researchers call this over-imitation. From a biological view, the Bobo children's exact copying of punches and phrases is an example of an evolved human readiness to learn from others, which helps children absorb a culture quickly.

Sex differences in physical aggression. Across many studies, boys show more physical aggression than girls from early childhood. John Archer's 2004 review of studies from many countries found the difference in all age groups and across cultures, largest for physical aggression. A large population survey in Quebec, Canada, found it already at 17 months: 5% of boys but only 1% of girls were often physically aggressive (Baillargeon et al., 2007). Archer (2009) argues that if boys simply learned aggression gradually from models, the gap should grow through childhood, and it does not.

Biological explanations point to hormones before birth. Girls exposed to unusually high levels of androgens (hormones such as testosterone) before birth, because of a condition called congenital adrenal hyperplasia, play more with boys' toys (Berenbaum & Hines, 1992). In one study their mothers also rated them as more aggressive than their unaffected sisters (Pasterski et al., 2007). These findings are not fully consistent across studies, and parents may treat these girls differently, so they suggest a contribution from biology rather than prove it.

The Bobo results show the same pattern as this wider literature. Boys copied more physical aggression than girls, but boys and girls did not differ in copying the model's words (Bandura et al., 1961, p. 579). Sex differences are usually smaller for verbal aggression.

Aggression starts early, and children learn to stop. Richard Tremblay's long-term studies in Canada found that physical aggression appears in most children before age two, is most frequent in the third and fourth years of life, and then declines as most children learn other ways to get what they want. Tremblay (2008) argues that children do not need to learn physical aggression. What they learn, mostly before school, is not to use it. The Bobo children, aged three to five, were near this peak. From this view, the aggressive model may not have taught aggression so much as weakened, for a short time, the self-control the children were still building. Bandura and colleagues themselves allowed that watching aggression "may serve to weaken inhibitory responses" (p. 580). The exact copied acts, such as hitting with the mallet while saying "Pow", still look like new learning.

Arousal. Having attractive toys taken away is frustrating, and frustration raises physical arousal: heart rate, muscle tension, readiness to act. Aroused children may do more of whatever behaviour is most available to them. In the test room, for children who had just watched aggression, that was hitting the doll.

Individual differences. Some children copied a great deal and some hardly at all. A combined analysis of 51 twin and adoption studies estimated that a little under half of the differences between people in aggression are linked to genetic differences (Rhee & Waldman, 2002). This figure describes variation within the populations studied. It does not mean that half of any one child's aggression is "genetic".

There is one twist that matters for this case. A twin study that used hits to a Bobo doll as its measure of aggression found almost no genetic influence. Its title gives the result: "Bobo clown aggression in childhood: Environment, not genes" (Plomin, Foch & Rowe, 1981). The sample was small, but it suggests that the Bobo measure picks up the situation more than the child's inborn tendencies.

What this lens values in the study

It would value the clear sex difference in physical aggression, which matches a large later research literature. It would also value the precise measurement of behaviour, which is what biological studies need to link to genes, hormones or brain activity.

What it would question

• Biology left out. The study treated the children as interchangeable learners and averaged them. It measured no temperament, arousal or health.
• Sex as a social category only. The paper explains boys' greater aggression entirely through social sex-typing. The biological lens says this cannot be decided from this study, because child sex was not assigned and could reflect both biological and social causes.
• Matching is not enough. Matching groups on teacher ratings of aggression balances some temperament differences, but only roughly.

Evidence from this tradition, and its limits

Caspi and colleagues (2002), following a large group of New Zealand children into adulthood, found that boys who had been maltreated were more likely to become antisocial adults, and that this link was much stronger for those with a low-activity version of a gene called MAOA. This is a gene-environment interaction: the effect of the environment depends on biology, and the reverse. Later studies have supported this specific finding only partly, so treat it as a promising example, not a settled fact.

Some writers have linked imitation to mirror neurons, brain cells first found in monkeys that respond both when an animal acts and when it sees the same act. This idea is popular but disputed. Gregory Hickok (2014) argued that it has been greatly overstated. Do not use mirror neurons in your journal as a proven explanation of the Bobo results.

A study this lens would design

1. Measure each child's temperament through parent questionnaires and observation before the study.
2. Record heart rate during the model session and the frustration step, using a small sensor.
3. Run the Bobo procedure as before.
4. Test whether children with higher baseline arousal or a more impulsive temperament copy more.
5. If possible, include twin pairs to separate genetic and shared-family influences.

This design does not replace the learning explanation. It asks for whom the learning effect is stronger, and why.

Try this

A newspaper headline reads: 'Bobo doll study proves boys are born more violent.'

Using the biological lens fairly, explain what is wrong with this headline.

Show the reasoning

The study did not measure any biological variable, so it cannot prove a biological cause. Child sex was not assigned by the researchers, so boys and girls differed in many ways at once: hormones, but also years of different treatment by parents, teachers and media. The authors themselves explained the difference socially.

The biological lens adds that other research, such as studies of prenatal hormones, suggests biology may contribute to boys' greater physical aggression. A fair statement would be: "Boys in this study copied more physical aggression. Other research suggests both biological and social causes for this kind of difference." The word "proves" and the phrase "born violent" are not supported.