Critical Thinking as Knowledge of Biases

Biases of memory: Who controls the present, controls the past

No discovery of experimental psychology is likely to be as potentially destabilizing to social and legal institutions as the recent discoveries about the frailty of human memory. One might simply note that all cognitive and perceptual biases noted above (and all the others too) apply to memory in all its guises: short-term, long-term, episodic, and what haven’t you. This is roughly true, but it’s worth getting a feel for just how significant this fact is.

Framing effects, to continue the example just canvassed, are known to have a powerful effect on the contents of memory – contents that appear to subjects to have all the detail and vivacity of the most reliable memory. In one famous experiment, two groups were shown video of one car running into another; one group was asked to estimate the speed of impact when one car hit the other, while the second group was asked to estimate the speed when one car smashed into the other. The second group systematically recalled the crash as occurring at a higher speed. While perhaps predictable, this effect in itself undermines the idea of memory as having its content fixed independently of the means of recall. Several days later, however, both groups were asked whether broken glass was visible in the video. Even though no broken glass was visible, members of the second “smashed” group had a significantly higher incidence of reporting a clear recollection of broken glass. They could see it in their minds, as clear as day.

Another well-known experiment involved inserting fictitious memories into the recall of young children and teens. (Innocuous memories, it should be noted!) These too were eventually recalled with a detail and phenomenology that made them indistinguishable from veridical, or at least veridically-based, memories. What exotic methods were employed to effect such a remarkable result?

It was this: repetition. Nothing more. In short, exactly the sort of thing that family and friends’ storytelling is apt present to any of us over many years. (Bear in mind that repetition is only a sufficient condition for false memories; it is unlikely to be necessary as well.)

Of course, certain constraints apply. It’s more or less impossible to convince a normal subject that she’s been to the Moon, since memory-fixation processes interact with general knowledge quite robustly. But within those broad constraints, the interaction with general knowledge is far from perfect; in one experiment, a subject was successfully implanted with the memory of having met Bugs Bunny during a childhood trip to Disneyland – even though it’s hardly a state secret that Bugs Bunny is not a Disney character.

The implications of such research for “eyewitness testimony” in legal contexts are hard to overestimate, for reasons that are not difficult to see. For our more humble purposes, however, such institutional concerns are set aside in favour of a deep personal caution towards our own memories, when they are in tension with the balance of independent evidence, and with the testimony of others, however sincere, when similar conditions obtain.