In my experience, children (and most people) just conceptualize infinity as a very large set, just as they perceive a tire a "circle", and think a square drawn

In my experience, children (and most people) just conceptualize infinity as a very large set, just as they perceive a tire a "circle", and think a square drawn on paper is made up of "lines". It requires years of thinking about these mathematical entities before people get a first glimpse of what they really mean, beyond a simplistic qualitative experience. To most people, children included, infinity is conceptually no different from the amount of sand on a beach. They just allow that it is simply not quantifiable. That turns off the brain. The more interesting thing to test, I would argue, would be the human mind conceptualizing a very, very large but ultimately finite set of something. That requires that we make a distinction between the discreteness of something and our ability to quantify it. That is a much more difficult concept to comprehend, and it must be understood before we can even begin to think about teaching a child about mathematical entities like infinity, circles, or lines.