Mental multitasking
The maximum # of variables a person can keep track of at a time is four, as mentioned in R A Wilson’s Illuminatus! Trilogy. In a new study by Graeme S. Halford, U of Queensland, 30 academics were given incomplete verbal descriptions of statistical interactions between fictitious variables, with graphs that represented the interactions. Participants had to complete given sentences to describe the interactions in the graphs, interactions involving 2-5 variables. After each problem, they also expressed how confident they were of their solutions. Needless to say, performance and confidence dropped as complexity grew until accuracy was no better than chance with five-way interactions. After the four- and five-way interactions, participants said things like, "I kept losing information," and "I just lost track."
How much can your mind keep track of? PhysOrg.com