Span of apprehension

The span of apprehension (SOB) is the number of items a person can apprehend or process simultaneously. So, for example, in subitizing studies, which refers to the rapid, accurate, and confident judgments of number performed for small numbers of items, subjects may know at a glance that there are six items on a tray. But if we increase the items to 13 then most people would have to count them individually.

This is taken to set a limit for working memory and in his famous paper George Millar argued that The Magical Number Seven, Plus or Minus Two set the range of oour processing capacity in such tasks.