  I find that exactly two stages can be seen directly in sequential free recall
distributions. These distributions show that the first three recalls come from
the emptying of working memory, recalls 6 and above come from a second stage
and the 4th and 5th recalls are mixtures of the two. A discontinuity, a rounded
step function, is shown to exist in the fitted linear slope of the recall
distributions as the recall shifts from the emptying of working memory
(positive slope) to the second stage (negative slope). The discontinuity leads
to a first estimate of the capacity of working memory at 4-4.5 items. Working
memory accounts for the recency effect. The primacy effect comes from the
second stage with a contribution also from working memory for short lists (the
first item). The different slopes of the working memory and secondary stages,
and that the two have different functional forms, accounts for the u-shaped
serial position curve. The total recall is shown to be a linear combination of
the content of working memory and items recalled in the second stage with
3.0-3.9 items coming from working memory, a second estimate of the capacity of
working memory. A third, separate upper limit on the capacity of working memory
is found (3.06 items), corresponding to the requirement that the content of
working memory cannot exceed the total recall, item by item. This third limit
presumably corresponds to the least chunked item. This is the best limit on the
capacity of unchunked working memory.
