In previous posts, I described the science behind the Four Mountains Test, a memory test which we developed using computer generated landscapes to assess the ability to recognize places from their layout even when the viewpoint changes. The test was designed from the outset to depend on a part of the brain, the hippocampus, which is important in forming new memories of the events we experience but also in maintaining a sense of direction and keeping track of where we are as we move about. We found that patients with damage to the hippocampus had particular difficulty with the test.
But if a damaged or deteriorating hippocampus impairs our ability to recognize places and find our way around, can a superfit hippocampus make a healthy person a supernavigator? We already know that acquiring spatial expertise can also lead to structural changes in the brain. London taxi drivers undergo an intense 3-4 year training programme before being licensed. During this time, part of their hippocampus grows. These are small changes, but they are only seen in successful trainees, not in unsuccessful trainees or ordinary members of the public. Is this the only way variations in brain structure come about, or is it possible that some people are born with brains that are already equipped to provide a more accurate sense of direction and location? To look into this we made a new, more difficult version of the Four Mountains Test which we could use with healthy people – scores on this version test shouldn’t be interpreted in terms of problems with the hippocampus, but they could help us compare healthy people’s memory for places and spot those who are much better than average.
The test has 30 items and is so hard that very few people can obtain full marks (less than 1 percent). There are four choices for each item, so by guessing you would expect to get 7 or 8 out of 30. Most people get around 20/30, far better than guessing but far from perfect. However we find quite a range of performance in the general population. Our experiments with the Four Mountains test are still underway, but there are tantalizing indications that performance on the task is related to the size of the hippocampus in healthy people. We were delighted when we were approached by the Channel 4’s Hidden Talent show to provide a test to help identify individuals with a special aptitude for finding their way around. The programme goes out on Tuesday 15th May at 9pm and you can see how the selected volunteers fared as their spatial skills were put to the test. At the selection stage Chris Bird and I briefed and tested all the participants under scientific conditions and were very happy with the way the sessions were run. Other spatial test you’ll see in the programme were adminstered by Hugo Spiers who appears on screen and supervised the navigation challenges the winning participants undertook. After the programme airs you can try out a short version of the test for yourself on the Hidden Talent Facebook page – Hugo will guide you through the process. Bear in mind that this is a cut down version of the real thing, with different test images. Nonetheless, you’ll be getting a pretty similar experience to the Hidden Talent participants – perhaps if you score 5 or 6 correct you have a hidden talent yourself.
From a scientific perspective one of the advantages of helping with the programme was that we collected data from a large number of people much more quickly and efficiently than would have been possible in the laboratory. Because of this we are able to uncover small effects which would not be detectable in smaller groups. For example, our preliminary analysis shows that men are very slightly better at the Four Mountains Task than women – the average score for men was 20.0/30 (median score 20) , was whereas for women it was 18.6/30 (median score 19) – a small but statistically reliable difference.
Here comparing averages does not give the whole story, there is very little difference in the proportions of men and women with typical scores but a much greater proportion of men gained the very highest scores (less than 10% of women get scores between 25-30, whereas 20% of men get scores in this range).
Previous research suggests that men and women tend to use different strategies for spatial memory, with women on the whole making more use of individual landmarks (which – purposely – are not much use in the Four Mountains test). Women also tend to perform less well than men on tests of mental rotation – the ability to imagine objects seen from a different point of view. Although imagining a place from a different perspective may rely on a separate mechanism it is clearly related to requirements of our test. These differences might play a part in the pattern we see in our experiment.
Although it is intriguing, this result doesn’t prove that there are biological differences between male and female abilities; for example it could be that men just try harder on this type of test or it might be that cultural gender differences come into play. To illustrate this if we had used pictures of football players instead of landscapes we might find that men on average score more highly than women, but it we would not attribute this to an innate difference in ability, since it would much easier to explain in cultural terms (in the UK at least, there are many more male than female football fans). Could something similar be going on with spatial skills? An interesting study compared men and women’s spatial skills in two closely-related NorthEast Indian groups, the Khasi and the Karbi, in which the roles of men and women are very different. In the Khasi tribe, property is inherited by daughters from mothers, whereas in the Karbi tribe women are not normally allowed to own land. Sex differences, seen clearly in the Karbi, were absent in the Khasi where women have a greater role, suggesting that cultural factors such as education, empowerment and competitiveness can influence the degree of sex differences in spatial skills.
Nonetheless we should not rule out the possibility that some of the differences we see in male and female performance on spatial tasks might have their roots in biological differences – however uncomfortable that may seem. Just as with other parts of our bodies there are structural differences in the brains of men and women and it would perhaps be surprising if these played no part in differences in the way we think and behave.