Researchers conducted interesting tests on H. M. in which they would present him with a performance task such as tracing shapes in the mirror. He would complete the task several times per day and for several days in a row. Each time, he would say "I’ve never seen this before in my life." Surprisingly, despite not remembering having done the task before, H. M. would get better and better on the task! What type of H. M.'s memory was impaired?