[1]http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2945821/ Among
  hearing people, the phonological loop is partially relied upon
  for working memory but not exclusively. There's a heuristic - a
  "rule of thumb" that's used as a baseline, of 7 distinct items
  in working memory, +/- two, but according to this study, people
  born deaf do not have diminished working memory capacity,
  although they DO have fewer "items" available to recall in a
  serial fashion - at least *seem-to*. IN this article the
  rule-of-thumb itself is questioned because the 7 +/-2 was rather
  over-reaching... and in fact people who have hearing, their
  levels of serial item recall is typically at the same levels as
  ASL users with only minor adjustments to lab study. So, point
  is: The "extra two" that are sometimes measured are _likely_
  echoing in the phonological loop. Meaning: There's not much
  significance to the phonological loop to working memory.

References

  Visible links
  1. https://l.facebook.com/l.php?u=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC2945821%2F&h=tAQHB8qcH