An expert on on cognitive neuropsychology speaks to us about his research on the seldom-discussed "dyslexia for numbers". Professor Brian Butterworth is based at University College London. Dyscalculia is a learning disability involving mathematics and numbers. Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Videos by Brady Haran Brady's other channels include: http://www.youtube.com/periodicvideos (Chemistry stuff) http://www.youtube.com/sixtysymbols (Physics and astronomy) http://www.youtube.com/DeepSkyVideos (Space stuff) http://www.youtube.com/nottinghamscience (Science and behind the scenes) http://www.youtube.com/foodskey (Food science) http://www.youtube.com/BackstageScience (Big science facilities) http://www.youtube.com/favscientist (Favourite scientists) http://www.youtube.com/bibledex (Academic look at the Bible) http://www.youtube.com/wordsoftheworld (Modern language and culture) http://www.youtube.com/PhilosophyFile (Philosophy stuff)