The role of "iwakan" in the asymmetric effect of additions versus deletions on recognition memory for pictures

Two experiments were conducted to examine whether stimulus impressions, that is "iwakan" (i.e. the feeling that something is strange (FSS)) could explain the relative superiority of additions or deletions in recognition memory. In Experiment 1, the participants observed either cat pictures or scene drawings in the study phase. They were then asked to judge whether each test picture had been altered. The results showed that deletions were detected more correctly and more quickly than additions in the cat pictures, whereas additions had an advantage over deletions in the scene drawings. In Experiment 2, the participants rated their impressions of altered cat pictures using two scales: the FSS scale, which had "pleasant-unpleasant" and "oddness" factors, and the P-FSS scale, which introduced an empathic "pitifulness" factor to the FSS scale. The results indicated that feelings of pity for the altered cat pictures explained the faster reaction time and better detection accuracy. These results suggest that the empathic evaluation of pitifulness caused the superiority of deletion in the cat pictures.