This seems related to these questions at a glance: http://cs.stackexchange.com/questions/9911/what-are-some-problems-which-are-easily-solved-by-human-brain-but-which-would-ta http://cs.stackexchange.com/questions/24312/what-would-show-a-human-mind-is-is-not-reducible-to-a-turing-machine But not quite, I am not asking about "time", but power. Also, I am not interested in the turing test. That said, my question can also be expressed as two parts: - *Is there a language, which cannot be recognized by any turing machine, that can be recognized by a human?* - *Is there a language, which cannot be decided by any turing machine, that can be decided by a human?* And vice versa. The "language" I am talking about is the "mathematical" language, not only a "human" or "programming" language: $$L \subseteq \Sigma^*$$ Since this is a question about computational power, I would make the following assumptions: - Human do not make mistakes (here I mean mistakes like copying the wrong character or computing arithmetics incorrectly, typical human errors) - There is no space limit (turing machine gets infinite tape, you get infinite medium to write) - There are no time constraints - However, the recognition/decision must be achieved within finite time. - And of course, in finite space Please give an example if you have an answer. Remember, this is a theoretical question, so practical issues are not in concern. **EDIT 1** OK, as someone pointed out, I will add the following assumptions. *Human* is probably not easy to define in precise mathematical words, so let's just assume "you". About a human recognizing a string in a language, I am talking about performing the same task the turing machine is "programmed" to do. Say, given a string, whether you (a human) can recognize it when it conforms to a set of rules, or decide whether it conforms to a set of rules or not. I am not sure if I can make the point clear enough... **EDIT 2** OK, to clarify, this *is* a question about model of computation, so yes, like André Souza Lemos mensioned, I am talking about "given a word $w$ and a language $L$, is sentence $w\in L$ decidable". I am not talking about a physical computer. **EDIT 3** OK, this is another idea I came up with. Does model of computation theory include inputs that are volatile by itself? That is, the input changes itself? That is probably not the "language recognition" problem though...