# Why do we make arithmetic mistakes?

I know the question does not strike as being specific to physics, but please, give it a look.
Human brains are considered complex computing machines and are rightly so as seen by the examples around us. Why then is it that we make conscious arithmetic errors( For example:
calculating 764*57656 mentally takes a lot of time and more often than not results in an error.)
even though an average person can say, judge distance and speed in reflex with a lot of precision?

phinds
Gold Member
On what do you base your statement that the errors are "conscious"? Do you think people make such mistakes on exams on purpose?

I wrote conscious; not on purpose. Maybe voluntary is the appropriate term here. What I mean to say here is why does our brain make arithmetic errors when it comes to making "conscious" or "voluntary" operations such as mentally adding two numbers. For example when someone asks us what 9*9 is, when know it is 81. This seems to suggest that our conscious self bases arithmetic calculations based on memory. However, next if asked what 109*9 is, we can logically link the operations 100*9 and 9*9 and then produce results results. But sometimes when the numbers are big, our brain fails us. I wonder why. It can be very precise in other involuntary operations such as releasing a certain specific quantity of a hormone, scheduling metabolic processes etc.

lurflurf
Homework Helper
Calculations are specific. The human brain is a powerful computer, but arithmetic is not one of its strengths.

Ryan_m_b
Staff Emeritus
Because the human brain is not a computer, don't take analogies too seriously. The brain is capable of what evolutionary pressures (or lack thereof) have caused it to be capable of. At no point was unconscious mental arithmetic (I.e the ability to do sums as instinctively as balancing, visual recognition etc) positively selected for.

1 person
I think it is because the brain needs a large amount of "temporary memory" to be able to solve large arithmetic problems, similarly to RAM on a computer. In the average brain, problems like these do not strike the consciousness as being essential for survival, so the brain doesn't try to waste an inordinate amount of energy. As far as being conscious about mistakes, I assume the OP means that we know that we made a mistake even though we might not have meant to do it or know exactly what the mistake is.

1 person
Thank you all. It is much clear now.

SteamKing
Staff Emeritus