If you run the same task on a pair of identical computers, you will end up getting the same results, even with the same response time.

But let's say you line two different person, and ask them the exact same question. Each will answer totally different, even if they are twins, raised in the same family, went to the same school and shared the same roof, and probably had the same experience in life. One of them may love carrots, one may not.

The question is, what is generating such different behaviour and way of thinking? Aren't they sharing the same genes?

If yes, the question is still standing.

If no, then we'll have another question:

If we create 2 identical clones of a person, raise them in the same situation, will they think identical too? If not, why? And what's the reason of this?

  • $\begingroup$ This is a classic and in my opinion interesting debate; nature versus nurture. It has filled textbooks, journal articles, and popular books. This question isn't a good fit for the site because it's too broad, unclear (what constitutes "thinking identically", how do you want to measure that), and a matter of opinion. If you're interested in the topic, consider narrowing down your question to "what evidence suggests they would think similarly" and ask over at cogsci.SE. This still, however, may be too broad. $\endgroup$
    – James
    Commented Apr 12, 2017 at 2:53
  • $\begingroup$ Thanks for your comment. I'm not expert in biology, my first question here. Please suggest / direct edit the question if you think it can be improved. I think you know what i'm after. As a computer programmer this question is bothering me for a long time, that why humans don't produce same results as computers. $\endgroup$
    – Johansson
    Commented Apr 12, 2017 at 3:40
  • 2
    $\begingroup$ Your example is flawed. If you have two identical computers (that is, identical hardware), and install Windows on one and Linux on the other, they will behave quite differently. Even two different versions of Windows or Linux will have differences, or two copies of the same version of Linux with different choices made during install. $\endgroup$
    – jamesqf
    Commented Apr 12, 2017 at 5:47
  • $\begingroup$ @jamesqf Even the same program with identical command-line parameters may produce different results or execute faster/slower if you use a random number generator or multithreaded code, or just have other programs running at the same time (the OS itself included). $\endgroup$
    – JAB
    Commented Apr 12, 2017 at 16:09
  • $\begingroup$ @jamesqf i mentioned to run the same task. $\endgroup$
    – Johansson
    Commented Apr 12, 2017 at 16:39

1 Answer 1


Your question has actually more to do with developmental biology and the origin of phenotypic variance in populations than with neuroscience.

Here is a list of factors which variance explain observed phenotypic variance in a population:

  • Genetics (incl. additive, dominance and epistatic variances)
  • Environment (incl. macro and micro environments)
  • Developmental noise (incl. cellular noise)
  • Epigenetic
  • All the covariances among above factors

Of course, when you consider a pair of monozygotic twin as your population, there is little to no genetic variance. They will also likely experience little epigenetic variance. Assuming they live together, practice the same sport, eat the same type of food, etc... then they will also experience little macro-environmental variance. Micro-envrionmental variance and developmental noise are probably the main factors causing these two hypothetical twins to differ.

You might want to read the post Why is a heritability coefficient not an index of how “genetic” something is? to better understand the current post.

  • 3
    $\begingroup$ Can you please expand on what remains unanswered? $\endgroup$
    – Remi.b
    Commented Apr 12, 2017 at 5:03
  • $\begingroup$ If you create 2 clones from an individual person (assuming it's technically possible) and put them under same circumstances, will their brain function identically? $\endgroup$
    – Johansson
    Commented Apr 12, 2017 at 16:41
  • $\begingroup$ Yes as you will still observe micro-environmental variance, variance due to developmental noise and epigenetic variance (and their covariances). If it is unclear you might want to read the post that I linked at the end of my answer. $\endgroup$
    – Remi.b
    Commented Apr 12, 2017 at 16:45

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