This may sound like a playground myth, but scientists are pretty much agreed that people whose ring finger is longer than their index finger were exposed to higher levels of testosterone in the womb. As such, finger length is thought to be a good indicator of several characteristics that are dependent on testosterone, such as athletic ability, anxiety, and spatial awareness.
To investigate, researcher Carl Pintzka from the Norwegian Competence Service for Functional MRI conducted an experiment to try and determine how testosterone affects brain activity when performing spatial awareness tasks, based on finger length.
He measured the fingers of 42 women in order to determine how much of the hormone they had been exposed to pre-birth, before asking them to navigate a virtual maze while having their brains scanned in an MRI machine.
Women with higher index finger to ring finger ratios – and therefore higher testosterone levels – displayed greater activity in brain regions such as the hippocampus, parahippocampal gyrus, and amygdala than those with lower ratios. Interestingly, however, this didn’t always correspond to greater navigational success, although it did tend to lead to higher scores when performing a separate task in which participants were asked to mentally rotate the virtual maze.
Pintzka also gave half of the women a 0.5 milligram dose of testosterone, while the other half received a placebo. Those that were given the hormone demonstrated greater activity in the medial temporal lobe, which once again led to better performance on the mental rotation task but not on the navigational task.
Publishing his work in the journal Behavioural Brain Research, though, Pintzka says that his results do not conclusively prove that testosterone levels are related to directional sense or spatial awareness.
Therefore, though some animal studies have shown that males often perform better than females at navigation tasks, this may not be entirely down to testosterone. It is also often claimed that men are more prone to mental disorders associated with high testosterone levels, such as Tourette’s and autism, while women tend to suffer from conditions like anxiety and depression, both of which are associated with low testosterone levels.
However, the results of this study suggest that measuring your finger may not be the most reliable diagnosis method.