According to research, the mean of improvement across hundreds of spatial intelligence training interventions tested was half a standard deviation for 2 to 6 months of training. For those who don’t know what a standard deviation is, it means that someone who was average (that is, better than 50% of the population but worse than the other 50% at spatial thinking) could train up to the 68th percentile in 2-6 months (the 68th percentile means that that person would become better than 68% of the population, although would still be below the remaining 32%). Someone at the 68th percentile who improved by half a standard deviation would reach the 84th percentile, this means that person would be above 84% of the population. Those with lower initial levels of spatial intelligence tend to exhibit greater and faster progress. Moreover, to date, psychologists have not found a limit to how much Spatial Intelligence can be improved; no training has ever been observed to improve spatial intelligence to a ceiling.