The task of organizational systems is to provide maximum information with the least cognitive effort.

The processing capacity of the conscious mind has been estimated at 120 bits per second.

The key to creating useful categories in our homes is to limit the number of types of things they contain to one or at most four types of things (respecting the capacity limitations of working memory).

Flow states don’t occur for just any old task or activity. They can occur only when one is deeply focused on the task, when the task requires intense concentration and commitment, contains clear goals, provides immediate feedback, and is perfectly matched to one’s skill level. This last point requires that your own skills and abilities are matched

the 3 x 5 card system is powerful. That is because it builds on the neuroscience of attention, memory, and categorization. The task-negative or mind-wandering mode is responsible for generating much useful information, but so much of it comes at the wrong time. We externalize our memory by putting that information on index cards.

“even if all knowledge could be found in books, where it is mixed in with so many useless things and confusingly heaped in such large volumes, it would take longer to read those books than we have to live in this life and more effort to select the useful things than to find them oneself.” A steady flow of complaints about

Satisficing is one of the foundations of productive human behavior; it prevails when we don’t waste time on decisions that don’t matter, or more accurately, when we don’t waste time trying to find improvements that are not going to make a significant difference in our happiness or satisfaction.

these situational categories can be planned far in advance. A

Complex questions like this are easily solvable with a trick I learned in graduate school—fourfold tables (also known as contingency tables). They are not easily solved using intuition or hunches. Say you wake up with blurred vision one morning. Suppose further that there exists a rare disease called optical blurritis. In the entire United States,