Rosenweig, Bennet, & Diamond (1972)

HL

aim

To investigate whether environmental factors — specifically a rich or impoverished environment — would affect the development of neurons in the cerebral cortex.

neuroplastcity

ability of the brain to change as a result of experience. Before this research, scientists believed the brain only changed up until a critical period in childhood — after which no further changes were thought possible

research design

A controlled laboratory experiment. Three male rats from a common litter were randomly allocated to one of three conditions: enriched (EC), control (CC), or impoverished (IC)

3 conditions

EC (enriched): 10–12 rats in a cage with toys and a maze. CC (control): 3 rats in a standard cage. IC (impoverished): individual rats in cages with no toys or maze. All had free access to food and water

how logn did the rats spend in their conditions and what happened afterward?

Typically 30–60 days, after which the rats were killed so researchers could study changes in brain anatomy

key findings

EC rats had a thicker and heavier cerebral cortex than IC rats. EC rats also showed significantly greater acetylcholine neuron activity in the cerebral cortex compared to IC rats

acetylcholine

important neurotransmitter for learning and memory — greater acetylcholine activity in EC rats suggests enriched environments enhance the brain systems underlying learning

follow-up study findings about duration of enrichment

Just 30 minutes a day in an enriched environment produced the same brain changes as continuous exposure in the original experiment — suggesting even brief enrichment can drive neuroplasticity

implications for humans

Since brain plasticity is assumed to follow similar patterns in animals and humans, the study implies that intellectual and social stimulation also affect the human brain. Poverty is now recognised as a major risk factor for children's cognitive development due to poor nutrition, lack of education, and poor health

research design strength

It was a highly controlled laboratory experiment, making it possible to establish a cause-and-effect relationship between environmental enrichment and brain changes.

confounding variables in enriched environment

It was unclear whether the changes were caused by the environment (toys) or social activity. A follow-up placing a single rat alone with toys for two hours showed no effect — the rat rested and groomed rather than playing, suggesting social interaction is necessary for enrichment to work.

confounding variable

Exercise — it is still unclear whether it was stimulation, social interaction, or physical exercise in the enriched environment that caused the brain changes, or how these variables interact

generalisation

The study used rats, so findings may not directly generalise to humans unless supported by hum

ethical concerns

Some rats were isolated in impoverished conditions causing potential stress and harm. All rats were killed at the end of the study. A cost-benefit analysis must weigh whether the scientific value of the findings justifies the harm done to the animals.

reliability

The results have been replicated many times, strengthening the reliability of the findings.