Does thinking out loud negatively affect one's ability to think internally? I'm a professional programmer, and I also practice math. During both, I constantly talk out loud, even for simple problems. However, when I'm around other people I suppress the talking and I feel like I lose a significant amount of clarity.

My assumption is that speaking out loud provides additional clarity because:


You're actually speaking, so you have to utilize more parts of your brain, including to physically move your mouth, which would decrease distraction/increase focus
You're hearing it, again utilizing more parts of your brain since you have to process external auditory signals


Whereas, the auditory simulation (essentially virtual stimulus) that the brain provides during silent thought is... not as intense as the real stimulus (speaking and hearing), thus utilizing less of the brain.

My question is not about whether thinking out loud helps you figure out a problem. 

My question is can long-term frequent thinking out loud have negative effects over one's ability to think internally/silently? 

And if there are negative long term effects can they be corrected in a short time by shifting your thinking back to a silent process?
Yes, anti-correlation between extrinsic and intrinsic brain networks may be altered by different practice. I give an example of how meditation affects anti-correlation between extrinsic and intrinsic brain networks.


  "Human experiences can be broadly divided into those that are external
  and related to interaction with the environment, and experiences that
  are internal and self-related."
  
  "Anti-correlation between extrinsic vs. intrinsic systems was stronger
  during FA (focused attention) meditation and weaker during NDA (non
  dual awareness) meditation in comparison to fixation (without
  mediation). However, correlation between areas within each system did
  not change across conditions. These results suggest that the
  anti-correlation found between extrinsic and intrinsic systems is not
  an immutable property of brain organization and that practicing
  different forms of meditation can modulate this gross functional
  organization in profoundly different ways."


Given these findings, your practice of speaking out loud may favor extrinsic brain network paths which could explain your loss of clarity when you suppress "thinking out loud" while among other people.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250078/