Kaufman, E. L., Lord, M. W., Reese, T. W. & Volkmann, J., “The Discrimination of Visual Number”, American Journal of Psychology, 1949, volume 62, page 498-525 is nonfiction science of “counting”. The diagram atop of colored stars are used to describe “subitizing”. Subitize is psychology of knowing the number of small sets, without the psychology of “counting”. This is not an error of calculation in hypercube space, depicted in the lower diagram. Relativity is physical numbers; however, developmentally “subitizing” is an arithmetic ability that is “usually” innate. Counting and subitizing are two different arithmetic abilities. Subitizing is going (diagram above) 1-star, 2-star, 3-star, 4-star without formal counting.