Tactual and visual alphanumeric suffix effects

Two experiments tested the effects of suffixes on the recall of tactual and visual sequences of alphabetic characters presented at 19 letters per min. Scoring techniques allowed for the differentiation of losses of item and order information. In Experiment I performance decrements were found for both modalities, which were mainly caused by item loss at the more recent part of the serial position curve in the suffix conditions. In Experiment II, these effects were replicated and a non-alphabetic suffix led to greater decrements for both modalities than an alphabetical suffix. While a suffix effect based on the loss of item information is consistent with a sensory trace interpretation of the suffix effect, the presence of a visual suffix effect with slow stimulus presentation is not. Additionally, the greater effect of the non-alphanumeric suffix challenges attentional interpretations. Some possible explanations are proposed.