&quot;But <i>this year</i> scientists have described a condition, aphantasia, in which some people are unable to visualise mental images.&quot;<p>Actually this was discovered by Sir Francis Galton more than 200 years ago: <a href="http:&#x2F;&#x2F;psychclassics.yorku.ca&#x2F;Galton&#x2F;imagery.htm" rel="nofollow">http:&#x2F;&#x2F;psychclassics.yorku.ca&#x2F;Galton&#x2F;imagery.htm</a><p>Nor is it particularly rare.<p>Perhaps the most interesting aspect is not the experience  itself, but the fact that people are so surprised when they discover that other people&#x27;s mental experience can be so different to their own.