In Ericsson’s seminal 1993 paper on the topic, titled “The Role of Deliberate Practice in the Acquisition of Expert Performance,” he dedicates a section to reviewing what the research literature reveals about an individual’s capacity for cognitively demanding work. Ericsson notes that for a novice, somewhere around an hour a day of intense concentration seems to be a limit, while for experts this number can expand to as many as four hours—but rarely more.
