Harvard Psychology Professor Discusses How Trauma Affects Memory

NPR's Ari Shapiro speaks with clinical psychologist Richard McNally about memory retention following traumatic events in light of the sexual assault accusations brought against Judge Brett Kavanaugh.

ARI SHAPIRO, HOST:

Soon after Christine Blasey Ford went public with her story about Brett Kavanaugh, critics began to question her memory. Ford says Kavanaugh and a friend assaulted her at a house party when they were teenagers. They are both in their 50s now. Ford has recalled the attack in gripping detail to The Washington Post. But she can't say whose house they were in or exactly how they ended up there. To shed light on how trauma affects memory, let's bring in Harvard psychology professor Richard McNally.

Welcome.

RICHARD MCNALLY: Thank you. Thank you for having me.

SHAPIRO: We know that memory in general is not entirely reliable and it can be difficult to precisely recall events from long ago. Does that change when we are talking about trauma and traumatic events?

MCNALLY: Yes. In fact, the stress hormones that are released during a terrifying experience tend to render the central features of that experience vivid and memorable. That said, the process does not operate like a videotape machine. So for example, it doesn't infallibly encode every detail of the experience. Nevertheless, the central features are typically retained - often all too well, as the case of post-traumatic stress disorder exemplifies, and sometimes at the expense of the peripheral details.

SHAPIRO: Do you find that these kinds of memories change over time the farther people get from the event?

MCNALLY: No, not necessarily. With traumatic events, they're fairly stable. I mean, memory is - it's a dynamic process. That's true. But to the extent that you've experienced the intense emotion at the encoding of the memories, it tends to render the central features of them quite stable. So you find this with war veterans, rape victims, victims of torture or natural disaster. They don't forget these things. They tend to be recalled quite vividly.

SHAPIRO: So you say the central event may remain vivid while peripheral details may not. That seems to come to bear in the Ford case, where she is saying she remembers the alleged incident very clearly but can't say for certain whose house she was at.

MCNALLY: Exactly. Right. Yeah, so the central features are those that the person's attending to. They're are often the most threatening, the most terrifying features of the experience; where the day in which it happened or the house or a dress or the day of the week it happened - these things may get scrambled up, forgotten because they're not really the ones that you are attending to at the very moment of terror.

SHAPIRO: Brett Kavanaugh categorically denies that anything like this assault ever happened. And he has suggested to Senator Orrin Hatch, Republican of Utah, that maybe this is a case of mistaken identity. Does it seem plausible to you that Ford may be remembering this traumatic incident correctly but not the cast of characters?

MCNALLY: That's possible. That's certainly possible that there's a mistaken identity. I really don't know. I don't know enough about the case, quite frankly. But eyewitness testimony is sometimes fallible. But the memory of the actual (inaudible) that a person might experience is unlikely to be garbled up to that extent.

SHAPIRO: Another variable here is alcohol. Ford told The Washington Post that Kavanaugh was stumbling drunk during this alleged incident. How does alcohol affect recall?

MCNALLY: Well, alcohol can sometimes impair the encoding and, therefore, the memory of experiences. The most dramatic examples are alcoholic blackouts, where the person is behaving and acting and so forth but has consumed so much alcohol that they have no memory of it at all. I'm not saying that's necessarily the case here, but alcohol does not improve memory. If anything, it tends to impair it.

SHAPIRO: Richard McNally is a clinical psychologist who teaches at Harvard University.

Thanks for joining us today.

MCNALLY: Thank you for having me.

(SOUNDBITE OF JOSHUA REDMAN AND THE BAD PLUS' "AS THIS MOMENT SLIPS AWAY")

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