A single-blind study means that the researchers were not aware which brain they were looking at. This prevents potential bias in the analysis of the data.

By repeatedly using the part of the brain related to spatial memory, this means that the neurons continue to fire.  The continued firing of the neurons, called long-term potentiation (LTP), results in gene expression which then leads to dendritic branching.  This dendritic branching is an increase in the grey matter which increases the volume of that part of the brain.

MRIs showed that the volume of the right posterior hippocampi correlated with the amount of time spent as a taxi driver. No differences were observed in other parts of the brain.

Since the size of the hippocampus increased the longer they worked as taxi drivers, this means that we cannot argue it was the size of their hippocampus that led to be taxi drivers in the first place.

When in the "stimulating" environment, the rats had several "toys" in the cage.   When a single rat was put in the cage alone, he tended not to play with the objects and instead rested and groomed himself. However, if he did play with the objects, then neuroplasticity was observed.  In cases where there were three rats in a cage together, there was more play and there was an increase in neuroplasticity.

The rats were killed and the volume of their brains was measured.

The studies both showed the role of behaviours in neuroplasticity, but they looked at different parts of the brain. Rosenzweig et al's study was a controlled laboratory experiment, which means a cause and effect relationship could be determined.

Research indicated that just 30 minutes a day in an enriched environment produced the same changes in the brain in rats as had been observed in the original experiment where rats were exposed to the EC condition for a much longer period of time.

Scopolamine has been used in several memory experiments. Scopolamine is a drug that blocks acetylcholine receptor sites - therefore, it is an antagonist.

A saline solution was injected as a placebo control. This was done to make sure that the fact of getting an injection alone was not responsible for a change in memory. An injection could result in an increase in adrenaline which would be a confounding variable. The injections were made directly into the hippocampus.

Although all participants in Troster and Beatty's study took part in all three memory tasks, they were randomly allocated either to the placebo group or the scopolamine group, just as Roger's and Kesner's rats.

In the facial recognition task, scopolamine did not impair recall - so, long-term memory was not affected.  It was affected, however, in both the map location test (spatial) and the words recalled (semantic) tests.