It looks like it’s self-reported data from the first year where there’s at least two days of logs. How could anyone extrapolate anything meaningful from two days of eating logs? So confusing.
The psychologist is Mihaly Csikszentmihalyi, and all of the quotes that the blog's author posted come directly from Csikszentmihalyi's book Creativity: Flow and the Psychology of Discovery and Invention. Csikszentmihalyi is most widely know for his term 'flow.'