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The self-administered interview (SAI©) is a booklet in which eyewitnesses write down their memories of an incident without assistance. The SAI can gather a significant amount of eyewitness information, and completing the SAI soon after witnessing an event can improve later recall. This study aimed to reveal the factor of effectiveness of the SAI and specifically focused on the method of handwriting. Participants watched a video and immediately recalled the event in the three conditions: SAI-writing, SAI-speaking, and free recall (speaking). One week later, participants again recalled the event via free recall. The results showed that participants in the SAI-writing condition reported more correct information than those in the other conditions at both time points. This suggests that a factor of effectiveness of the SAI is the method of writing. Thus, initial written recall using the SAI could facilitate later recall in police investigative interviews.

Two experiments were conducted to demonstrate that skilled soroban (Japanese abacus) operators can improve digit memory retention by manipulating the beads of a ‘mental soroban’ which is analogous to the actual one. In Experiment 1, soroban experts and control subjects were given two digit memory tasks. In one task, pictures of a soroban figure and in the other, pictures of digit sequences, were presented to the subjects during the retention interval. Soroban experts experienced greater interference from presentation of the soroban figures than the digits; on the other hand, the reverse was true in the control subjects. In Experiment 2, ther soroban experts and control subjects were given the same digit memory tasks under three conditions—soroban pictures, pictures of digit sequences, and human faces were presented to subjects during the retention period of 15 s. The soroban experts were more affected by the presentation of the soroban figures than by the faces or digits, whereas the controls showed more interference from the digits than by the presentation of faces or soroban pictures.