Working memory is a core cognitive process for short-term storage and manipulation of both sensory information and information already stored in our long-term memory. It is crucial for our everyday functioning. Human cognitive performance is highly dependent on the general limitations of working memory.
In 1956 Geroge Miller argued that the capacity of working memory in terms of memorizable chunks, or meaningful information collections, is the magical number seven, plus or minus two. In the Miller’s memory span studies the subjects had to remember at least 50% of the trials in the correct order. Should one want to remember ereverything correctly, the capacity is closer to the magical number 4 proposed by Nelson Cowan in 2001.
However, more recent studies indicate that working memory does not handle information in discrete slots. In their excellent article Wei Ji Ma, Masud Husain and Paul Bays review the changing concepts of working memory. It appears that in addition to the number of chunks, the more details a memorizable chunk has, or the finer the details, the less we remember. For example, as Nikos Gorgoraptis and colleagues showed, if we see a group of items and later have to remember the colour of one of the items, the more items we saw, the more error we make in trying to point to the right coulour in a colour palette. If we get a cue on which item is the most probable target, we are able to memorize details, for example the orientation, of the item better than if the cue is absent. Obviously, if we get a cue, we err most in the details of uncued items if probed nonetheless.
Evidence against slot working memory model.
By Ma et al. 2014 (adapted from Gorgoraptis et al. 2011).