Major stimulus dimensions determining detection of simulated breast lesions

Five adult humans palpated silicone breast models in a lump-detection task. The effects on detection of several lump and model characteristics were studied in three phases, using both discrete trial (restricted search procedure) and “free response” (free search procedure) psychophysical methods. Size and depth of fixed steel lumps were varied in Phase 1. Depth and hardness of uniformly sized, fixed lumps were varied in Phase 2. The presence and depth of simulated breast nodularity were also studied in Phases 1 and 2. In Phase 3, all breast models were uniformly nodular and lumps varied along dimensions of size, depth, hardness, and fixation. In Phase 1, lump detection was greatest with maximum lump size and minimum depth within the model. Neither lump hardness nor depth differentially influenced detection of the fixed lumps in Phase 2. When breast lumps were mobile, in Phase 3, size and hardness were major stimulus dimensions determining detection. These results suggest physical parameters for realistic breast models and lumps to be used in training effective breast self-examination and breast lump detection.