For a long time Milner thought that H.M.’s memory deficit applied to all areas of knowledge. Then she made a remarkable discovery. She asked H.M. to trace the outline of a star while looking at his hand, his pencil, and the paper in a mirror. Everyone who tries this tracing task makes errors on the first day, drawing outside the line of the star and having to adjust back in, but people with normal memory improve to almost perfect performance by the third day. If H.M.’s memory loss applied to all areas of knowledge, he should show no such improvement. Yet after three days, and despite having no
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