16 right-handed male taxi drivers that had completed the "Knowledge" test and had at least 1.5 years with their license were chosen for the test.
The taxi drivers' MRI's were compared with the MRI scans of 50 right handed males who did not drive taxis. These control MRI's were taken from an MRI database.
The study is correlational in nature as the IV is not manipulated by the researcher. The researchers were looking to see if there was a relationship between the number of years of driving a taxi and the anatomy of one's brain. It was also a singleblind study that is, the researchers did not know whether she was looking at the scan of a taxi driver or a control.
1 year driver a taxi
10 years driving a taxi
The data from the MRI was measured using two different techniques: voxelbased morphometry(VBM) and pixel counting. Voxelbased morphology (VBM) was used in this study to measure the density of grey matter in the brain. Pixel counting consists of counting the pixels in the images provided by the MRI scans in order to calculate the area of the hippocampus.
Pixel counting revealed that the posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects and the anterior hippocampi were significantly smaller.
VBM 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. Maguire argues that this demonstrates that the hippocampus may change in response to environmental demands.