Contemporary studies: Brendgen et al. (2005); McDermott (2008) or Hoefelmann et al. (2006)

Psychology (XPS01) · Pearson Edexcel International AS Level · 5 min read · Updated: 7 Sept 2026

Introduction to Contemporary Studies in Biological Psychology

Welcome! In our study of Biological Psychology, we look at how our physical bodies—our brains, genes, and hormones—influence the way we act. While the "classic" studies (like Raine et al., 1997) gave us a foundation, contemporary studies use modern methods to answer specific questions about aggression and sleep.

In this chapter, we will cover the compulsory study by Brendgen et al. (2005) and the two optional studies: McDermott (2008) and Hoefelmann et al. (2006). Depending on your school, you may focus more on one of the optional ones, but everyone needs to know Brendgen!

Quick Tip: When studying these, always think about the "Big Six" evaluation points: Generalisability, Reliability, Application, Validity, Ethics, and Objectivity (GRAVEO).

1. Compulsory Study: Brendgen et al. (2005)

"Examining genetic and environmental effects on social aggression: A study of 6-year-old twins"

The Big Question: Is aggression something we are born with (nature), or is it something we learn from our environment (nurture)? More specifically, does this change depending on whether the aggression is physical (hitting) or social (spreading rumors)?

Aims

1. To see if social aggression and physical aggression are caused by the same factors (genes vs. environment).
2. To see if physical aggression leads to social aggression over time.

Method & Procedure

Participants: 234 pairs of 6-year-old twins from the Montreal Newborn Twin Study.
- MZ (Monozygotic) twins: Identical twins who share 100% of their genes.
- DZ (Dizygotic) twins: Non-identical twins who share about 50% of their genes.
Data Collection: The researchers used peer ratings (classmates pointing at pictures of children who fit certain descriptions) and teacher ratings (questionnaires) to measure aggression.

Results

Physical Aggression: There was a much higher correlation in MZ twins than DZ twins. This suggests physical aggression is mostly genetic (Nature).
Social Aggression: The correlations between MZ and DZ twins were similar. This suggests social aggression is mostly caused by environmental factors (Nurture).
The Link: Children who were physically aggressive were more likely to become socially aggressive later, possibly because they learn more "subtle" ways to be mean as they develop.

Key Takeaway

Physical aggression is largely in our DNA, but social aggression is something we pick up from our surroundings!

2. Optional Study: McDermott (2008)

"Monoamine oxidase A gene (MAOA) predicts behavioural aggression following provocation"

The Big Question: Does the "Warrior Gene" (MAOA) actually make people more aggressive, or does it only happen if someone provokes them first?

Aims

To investigate the link between the low-activity MAOA gene (MAOA-L) and aggressive behavior when a person is provoked.

Method & Procedure

Participants: 78 male subjects divided into two groups: those with the high-activity gene and those with the low-activity (MAOA-L) version.
The Task: A vocabulary-earning task where participants could earn "points" (money). A "fake" opponent would then "steal" some of their points.
The Aggression Measure: The participant could punish the opponent by forcing them to eat unpleasantly hot spicy sauce. They could choose the amount of sauce given.

Results

When a large amount of points were stolen (high provocation), those with the MAOA-L gene were significantly more likely to retaliate with more hot sauce.
When only a small amount was stolen (low provocation), the difference between the gene groups was much smaller.

Key Takeaway

The MAOA gene doesn't just make you aggressive "out of nowhere." Instead, it makes you more likely to overreact to a provocation. It is a mix of biology (the gene) and the situation (provocation).

3. Optional Study: Hoefelmann et al. (2006)

"Behaviors associated to sleep among high school learners"

The Big Question: How do our daily habits—like watching TV or drinking soda—affect how much sleep we get?

Aims

To describe sleep duration and identify behaviors associated with poor sleep in Brazilian high school students.

Method & Procedure

Research Method: This was a correlational study using a cross-sectional design (looking at a snapshot of people at one time) and prospective analysis.
Participants: Over 4,000 students (ages 14–24) in Florianópolis, Brazil.
Data: Students completed questionnaires about their sleep (duration and quality) and their lifestyle habits.

Results

The researchers found that short sleep duration was linked to:
- Working during the day.
- High screen time (watching TV for more than 2 hours a day).
- High consumption of caffeine (sodas/coffee).
- Low physical activity.
Many students were getting less than the recommended amount of sleep for their age.

Key Takeaway

External factors (zeitgebers) and lifestyle choices significantly disrupt the natural circadian sleep-wake cycle in teenagers.

Evaluation: Thinking Like a Psychologist

When you are asked to evaluate these studies in the exam, use these prompts to help you:

Generalisability:
- Brendgen: 6-year-olds are very specific. Can we apply this to adults?
- McDermott: Used only males. Can we apply this to females?
- Hoefelmann: Large sample, but only in one city in Brazil. Is it culturally biased?
Reliability:
- Brendgen: Used both teacher and peer ratings. If both groups agree, the data is more reliable.
- McDermott: Controlled lab setting makes it easy to replicate.
Validity:
- Ecological Validity: Giving someone "hot sauce" in a lab (McDermott) isn't the same as real-world violence. Does it measure "real" aggression?
- Subjectivity: Peer ratings (Brendgen) might be biased by popularity rather than actual aggression.
Ethics:
- McDermott: Participants were provoked and encouraged to be "aggressive," which could cause psychological stress.
- Brendgen: Asking children to point out "mean" classmates could lead to bullying or hurt feelings.

Quick Review Box:
- Brendgen: Twins + Physical (Genes) vs. Social (Environment).
- McDermott: MAOA gene + Hot Sauce + Provocation.
- Hoefelmann: Sleep + TV + Caffeine + Brazilian Teens.

Don't worry if the names and dates seem hard to remember at first! Just focus on the story of each study: Who was tested? What did they do? What did they find? The rest will follow with practice.

Quick check

Can you answer these now?

Open each question to check the key ideas from this chapter.

What was the primary aim of the study by Brendgen et al. (2005)?

To investigate if social and physical aggression are caused by the same factors (genes vs. environment) and if physical aggression predicts social aggression over time.

How did Brendgen et al. (2005) differentiate between genetic and environmental influences in their participants?

They compared 234 pairs of twins, including Monozygotic (MZ) twins who share 100% genes and Dizygotic (DZ) twins who share 50% genes.

What did Brendgen et al. (2005) find regarding the causes of physical versus social aggression?

Physical aggression was found to be mostly genetic (nature), while social aggression was primarily caused by environmental factors (nurture).

What was the aim of McDermott's (2008) study on the MAOA gene?

To investigate if the low-activity MAOA gene (MAOA-L) predicts aggressive behavior specifically when a person is provoked.

In McDermott's (2008) study, how was aggression measured in the laboratory?

Aggression was measured by the amount of unpleasantly hot spicy sauce a participant chose to give to an opponent who had stolen their points.

What was the key conclusion of McDermott (2008) regarding the 'Warrior Gene'?

The MAOA-L gene makes individuals more likely to overreact to provocation, rather than making them aggressive 'out of nowhere.'

What factors were linked to short sleep duration in Hoefelmann et al.'s (2006) study?

Short sleep was associated with working during the day, high screen time (over 2 hours of TV), high caffeine consumption, and low physical activity.

In terms of GRAVEO, what is a major validity concern for McDermott (2008)?

Low ecological validity, because forcing someone to eat hot sauce in a lab setting may not accurately reflect how aggression works in real-world violent situations.

What ethical concern was raised regarding the methodology of Brendgen et al. (2005)?

The use of peer ratings, where children point out 'mean' classmates, could potentially lead to bullying, labeling, or hurt feelings among the participants.

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