The Pointed Shape of a Knife Influences Eyewitness Perception

We examined the hypothesis that a pointed knife attracts particular attention because of its pointed shape. Using a visual search task method, we asked 33 participants to search 3 × 3 matrices containing outlines of knives with pointed blades such as chef’s knives and knives with rectangular blades such as Chinese chopping knives and to determine whether the matrices contained identical or non-identical knives. The participants found a pointed knife within a background of knives with rectangular blades more quickly than under the reverse condition. This result indicates that the pointed shape of a knife has an attribute that captures human attention and suggests that the visual features of a weapon affect eyewitness perception. This research would benefit forensic investigations in countries such as Japan, where gun ownership is banned and perpetrators use knives more often than firearms.