The human brain is generally poor at generating random numbers. For example, if you ask a human to generate a random sequence of numbers and compare it to a sequence generated by a computer, the human sequence will have fewer and shorter strings of the same number (i.e. a human generated string looks closer to 1094876847631098785, while actual randomness would look closer to 12522313888815219). When asked to pick a number at random humans disproportionately pick certain numbers. It is even possible to build an algorithm that can determine who made a specific sequence. Reddit