Psychology (9990) | Hassett et al. (monkey toy preferences)

🧠 Core Study: Hassett et al. (2008) – Monkey Toy Preferences

Welcome to one of the most fascinating studies in the Biological Approach! Hassett et al. didn't study children directly, but observed monkeys to investigate a classic question: Are boys and girls naturally drawn to certain toys, or is it all down to how we are raised?

This study provides key evidence that certain preferences might be built into our biology (our hormones and evolution) rather than being purely learned from society. Get ready to meet the Rhesus macaques!

1. The Biological Approach Context

The **Biological Approach** assumes that our behaviour, cognitions, and emotions are primarily determined by physiological factors, such as the brain, hormones, genetics, and evolution (Syllabus p. 5).

Hassett et al. specifically addresses the famous Nature versus Nurture debate:

• Nature: Toy preference is biological (determined by hormones, especially pre-natal exposure to androgens).
• Nurture: Toy preference is learned through socialisation (e.g., parents rewarding 'correct' play, peer pressure).

The core idea here is that if monkeys—who have less human-like social rules—show the same preferences as human children, then the behaviour is likely determined by innate biology (Nature).

Psychology Investigated:

• Sex differences in behaviour.
• The role of hormones (specifically relating to play behaviour).
• Play and socialisation (though focusing on the biological root of play).

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2. Background and Aim

Background:

Studies on human children consistently show that boys generally prefer action/vehicle toys, and girls prefer dolls/nurturing toys. However, it's difficult to separate biological factors from the intense socialisation children experience (e.g., gender-specific marketing or parental influence).

Rhesus macaques are an ideal species to study because:

• They share 93% of their genes with humans.
• They display similar play behaviours to human children.
• Their social environment is less complex, making pure social learning a less powerful explanation for sex differences than in humans.

Aim:

To investigate whether rhesus monkeys show sex differences in toy preferences that parallel those observed in human children, thereby providing evidence for a biological explanation (the role of hormones) of these preferences.

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3. Detailed Procedure (How the Study Was Done)

Hassett et al. used a **laboratory experiment** combined with **structured observation**.

A. Sample and Participants

• Sample Size: 135 Rhesus Macaque monkeys.
• Demographics: Included juvenile (young) and adult monkeys, both male and female.

B. The Materials (Independent Variable)

The researchers used three categories of toys, carefully chosen based on existing research into human and primate play:

1. Male-Typical Toys: Objects associated with activity and rough movement (e.g., a small fire truck, wheeled cart, ball).
2. Female-Typical Toys: Objects associated with nurturing or quiet/calm behaviour (e.g., a plush doll, cooking pot, small pail).
3. Neutral Toys: Objects that did not usually elicit a sex difference in play (e.g., a picture book or a rectangular cube).

C. The Procedure and Data Collection

1. **Setting Up:** The monkeys were observed in their home cage/group environment, but the toy selection was introduced in a controlled way (a **controlled observation**).

2. **Observation Period:** The monkeys were presented with a set of these toys in multiple 10-minute observation periods.

3. **Data Collection (DV):** The **Dependent Variable** was the amount of time the monkeys spent interacting with each type of toy (Male-typical, Female-typical, Neutral).

4. **Measuring Interaction:** Interaction was strictly defined and recorded using a **behavioural checklist** (structured observation). Interaction included:

• Touching the toy.
• Sitting within one arm's length of the toy.
• Holding or manipulating the toy.

5. **Control:** Data from a previous study on human children’s toy preferences was used for comparison, ensuring the conclusions drawn about the parallel preferences were based on the same categories of toys.

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4. Key Results and Conclusions

A. Quantitative Findings (The Main Results)

The results showed highly significant sex differences in how the monkeys interacted with the toys:

1. Male Monkeys: Spent significantly more time interacting with **Male-Typical Toys** (trucks, wheeled objects) than with Female-Typical Toys.
2. Female Monkeys: Spent significantly more time interacting with **Female-Typical Toys** (dolls, cooking pots) than with Male-Typical Toys.
3. Neutral Toys: Both male and female monkeys interacted with **Neutral Toys** (e.g., picture book) for moderate and equal amounts of time.

Did you know? The toy preferences were consistent regardless of whether the monkeys were juveniles or adults, suggesting the preference is fixed early on.

B. Conclusion

Hassett et al. concluded that sex differences in rhesus monkey toy preferences parallel those observed in human children. Since the monkeys' behaviour is assumed to be less influenced by complex socialisation than children's, this strongly supports the hypothesis that these preferences are due to **biological factors**, such as prenatal exposure to androgens (male hormones), rather than solely social learning.

Key Takeaway: The similarity in toy preferences across different species (monkeys and humans) suggests a shared evolutionary and hormonal influence (Nature) on gendered play behaviour.

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5. Evaluation: Strengths and Weaknesses

✅ Strengths of Hassett et al.

• High Controls (Lab Study): The study used carefully categorised toys and defined 'interaction' precisely using a behavioural checklist. This standardisation increases the **reliability** of the measurements (other researchers could replicate the procedure).
• Objective Data: Using observations and recording quantifiable data (time spent interacting) means the data is **objective**, reducing researcher bias compared to self-report methods.
• Support for Biological Approach: By using a non-human species, Hassett could argue that socialisation (nurture) was a less significant factor, providing strong evidence for the role of biology and hormones (nature) in shaping behaviour.

❌ Weaknesses of Hassett et al.

• Ethical Issues (Animals): Research on animals must adhere to strict ethical guidelines (see Section 6). Although the monkeys were observed in their home environment (minimising stress), the study still involves manipulating their environment and housing them in captivity.
• Anthropomorphism: The researchers are imposing **human concepts** (gender roles, "boy toys" vs. "girl toys") onto a monkey population. The monkeys don't know what a 'truck' or 'doll' means in a human social context.
• Generalisability: While the *aim* was to generalise the biological mechanism, we must be careful. Rhesus monkeys are not humans, and their social structures, though simpler, still involve learning. The findings provide *support* but not definitive proof for humans.

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6. Issues and Debates

A. Nature Versus Nurture

This study is a classic example of research supporting the Nature side of the debate. The fact that monkeys, who are exposed to fewer gender role stereotypes than human children, display the same preferences suggests a strong biological determinant (hormones or evolutionary mechanisms) is at play.

However, the study is not purely Nature. While the initial preference may be innate, the specific ways monkeys interact (play and **socialisation**) are still refined through their interactions within the troop (Nurture).

B. The Use of Animals in Psychological Research

Since Hassett et al. used Rhesus monkeys, we must evaluate the study using the ethical guidelines for animal research (Syllabus p. 11):

• Minimising Harm (and Maximising Benefit): The benefit (understanding the biological roots of human behaviour) must outweigh the potential harm. The study observed natural behaviours and did not involve painful procedures.
• Replacement: Could this study have been done using human children? The researchers argue no, as the control required (removing social influence) necessitated using a non-human species.
• Procedures: The procedure was a simple, non-invasive observation in their housing area, reducing distress (no deprivation or aversive stimuli were used).
• Species/Housing/Numbers: The study used a reasonable number of monkeys (135). The animals were observed in their familiar social groupings (home cage).

It is important to remember that using animals is usually only justified if the research question cannot be answered using human participants, as Hassett argued regarding the influence of socialisation.

C. Application to Everyday Life

The findings have a significant application to understanding human development. If toy preferences are biologically rooted, it suggests that:

• Parents should not worry if their children gravitate towards gender-typical toys, as this may be a natural, hormonal preference.
• However, the research doesn't stop social influence from still being important. We can use this knowledge to promote inclusive play, understanding that some resistance to non-typical toys might stem from innate biases, requiring more conscious effort from parents and educators.