Letters of high frequency show a significant advantage over letters of low frequency in letter naming,[1] same-different matching,[2] and visual search.
[3] Letters of high frequency are recognized faster than letters of low frequency.
[4] Appelman and Mayzner (1981) in their re-analysis of the studies concerning letter frequency effect have found that in 3 out of 6 studies using reaction times (RTs) as a dependent variable the letter frequency correlated significantly with RTs.
[5] Majority of studies on letter frequency effect failed to find a significant letter frequency effect.
[6] These studies, however, used the same-different matching task[6] in which the participants see two letters and are to respond if these letters are same or different.