Case Study

Based on the details provided in this case, explain what a 'dissociation' between memory systems means in the context of H.M.'s post-surgical cognitive abilities. How does his preserved short-term memory alongside his deficit in memory consolidation support this dissociation?

Case context: A cognitive psychologist is studying the organization of human memory systems. They review the clinical case of Henry Molaison (H.M.), who had large sections of his hippocampus surgically removed in 1953 to treat severe epilepsy. Post-surgery, H.M. could hold a brief conversation and repeat a string of numbers immediately, but he could not form new long-term memories of the conversation or the researcher. The researcher notes that H.M.'s IQ and personality remained unaffected.

Question: Based on the details provided in this case, explain what a 'dissociation' between memory systems means in the context of H.M.'s post-surgical cognitive abilities. How does his preserved short-term memory alongside his deficit in memory consolidation support this dissociation?

Sample answer: A dissociation indicates that different cognitive functions (like short-term and long-term memory) are controlled by separate, independent systems in the brain. In H.M.'s case, the surgery left his short-term memory intact but permanently destroyed his ability to perform memory consolidation (transferring new information to long-term memory). This clear split shows that short-term retention and long-term consolidation are distinct processes that rely on different neural structures, with the hippocampus and temporal lobes specifically required for consolidation rather than short-term storage.

Key points:

  • A dissociation shows that short-term and long-term memory operate via distinct systems.
  • H.M.'s short-term memory, IQ, and personality remained intact after the removal of the hippocampus.
  • H.M.'s ability to transfer new information into long-term memory (consolidation) was permanently lost.
  • This pattern demonstrates that the temporal lobes and hippocampus are critical for memory consolidation rather than maintaining short-term memory.

Rubric: The student must demonstrate comprehension of a 'dissociation' by explaining that it shows short-term and long-term memory are separate systems. They must explain that H.M.'s ability to keep short-term memories intact while failing to consolidate new long-term memories serves as the evidence for this separation, and link this to the role of the temporal lobes/hippocampus in consolidation specifically.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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