Henry Gustav Molaison, known as H.M., was unable to form new declarative memories. He suffered from what psychologists call

A) psychogenic amnesia.
B) retrograde amnesia.
C) retroactive amnesia.
D) anterograde amnesia.

H.M. was unable to form new declarative memories, which is characteristic of anterograde amnesia. Retrograde amnesia refers to the loss of memories that occurred before the onset of amnesia, and retroactive amnesia refers to the inability to remember events that occurred after a traumatic event. Psychogenic amnesia is a type of amnesia that is thought to be caused by psychological factors rather than physical brain damage.