Interaction Between Memory Decay, Visual Span, and the Size of the Letter String

Background: It is believed, there are significant interactions between letter recognition
accuracy and string length (which in turn depends on the serial position of the letter
within the string) due to combined limitations presented by both memory load and
memory decay. The goal of this study is to investigate the visual span shrinkage due to
memory load and decay with increasing letter string length. Methods: Ten adult subjects
were used in this study to measure letter recognition accuracy with random 3-letter
trigrams and 5-letter pentagrams on a computer screen at varying letter positions to the
left and right of fixation. Subjects were asked to report all 3 or all 5 letters in complete
report and single letter in partial report. Letters were black lowercase Courier with
contrast appearing for 100 milliseconds. Results: Results will be aimed to three specific
goals: 1) To quantify the effects of report condition on letter recognition accuracy for two
string length conditions; 2) To investigate the effect of report condition on letter
recognition accuracy as a function of the serial position of a character within trigrams and
pentagrams; 3) To investigate the effect of report condition on letter sequence recognition
accuracy as a function of character’s inner and outer position within the trigram and
pentagram. Conclusions: Visual span decreased significantly with increasing strings
length. Higher cortical processes such as memory load and decay as well as crowding
effects play an important role in the ever-changing visual span.