I told the person about the bakery that I'd recently eaten, that it was near my home. My wife told me that the cookies I ate were oatmeal raisin.
Why did I make this mistake? Is this an early sign of dementia? Should I go to my doctor?
Is forgetting the details of a dessert a good thing, because we are so busy with so many details in our daily lives?
I have been studying human perception and cognitive functioning for more than 30 years. We are working on new ways to explore this kind of error.
Is it a bad thing that these memory mistakes are caused by faulty mental processing? Is it a good thing that they are a side effect of a cognitive system with limited capacity?
We're leaning towards the latter because memory errors may indicate a way in which the human cognitive system is "optimal" or "rational."
People are rational.
Cognitive scientists have pondered if human cognitive function is rational. In the 1960s, Daniel Kahneman and Amos Tversky conducted research on this topic. They found that people use "quick and dirty" mental strategies.
When asked if the English language has more words starting with the letter "k" or with "k" as the third letter, most people say there are more words starting with "k."
People reach this conclusion by thinking of words that start with "k" and with "k" in the third position, and noticing that they can think of more words with that initial "k." The "availability heuristic" is a strategy referred to by Kahneman and Tversky.
Heterogeneity often yields good results, but sometimes it doesn't. Human cognitive function is not optimal according to Tversky and Kahneman. The English language has more words with "k" in the third position than it does with "k" in the first position.
Is it the best it can be?
In the 1980s, research began to suggest that human perception and cognitive function might be optimal. Several studies have shown that people combine information from multiple senses in a way that is optimal despite the noise in the signals.
Some instances of seemingly optimal behavior are actually the opposite. People underestimate the speed of moving objects.
Scientists theorize that human visual motion perception is not optimal.
A recent study shows that the most optimal sensory interpretation is one that combines visual information about the speed of an object with general knowledge that most objects in the world tend to be stationary or slow moving.
This interpretation underestimates the speed of an object when it is noisy or low quality.
It is possible that these errors are inevitable when visual information is imperfect and people are actually seeing motion speeds as well as they can be perceived.
Scientists found similar results when studying humans. When information is ambiguous or uncertain, people often make errors when remembering, reasoning, deciding, planning, or acting.
When performing cognitive tasks, the best strategy is to combine information from data, such as things one has observed or experienced, with general knowledge about how the world works.
The researchers found that the inevitable errors made by optimal strategies resemble the errors people really make, suggesting that people may be performing cognitive tasks as well as they can be performed.
There is mounting evidence that errors are inevitable when reasoning with ambiguous inputs. Errors are not indicators of faulty mental processing if that is the case. People's perceptual and cognitive systems may be working well.
Your brain is under constraints.
Human mental behavior can be constrained. People can't attend to everything at the same time, because they have limited capacity for paying attention.
You can't remember everything if you have limited memory capacity. The need to act in a timely manner is one of the external constraints. It is possible that people can't always perform optimal perception.
If there were no constraints, your perception and cognitive abilities would not be as good as they could be.
Consider a problem that requires you to think about many factors. If you can't think about all factors at once, you won't be able to think of the best solution.
If you think about as many factors as you can at the same time, and if these are the most important factors for the problem, you'll be able to come up with a solution that is as good as possible.
There are limits to memory.
The "resource-rational" approach emphasizes "constrained optimality." We have developed a resource-rational approach to memory. Our framework thinks of memory as a communication channel.
It's as if you're sending a message to your future self when you place an item in memory. The channel has limited capacity and can't transmit all of the details of a message.
A message retrieved from memory at a later time may not be the same as the message placed into memory at the earlier time. That is the reason memory errors occur.
If your memory store can't keep up with all the details of the items it has, then it would be wise to make sure that the important ones are kept up to date. It should be the best it can be in limited circumstances.
People tend to remember task-relevant details and forget task-irrelevant details. People tend to forget the fine details of an item that is placed in memory.
People fill in the missing details with the most frequent or commonplace properties when this happens. The use of commonplace properties when details are missing is a type of strategy that will often work well but sometimes fail.
Why did I recall eating chocolate chip cookies when I had eaten oatmeal raisin cookies?
I forgot the fine details of my experience eating cookies, but I filled in the details with the most common properties, such as cookies with chocolate chips.
This error shows that my memory is working as it should. That's a good thing.
Robert Jacobs is a professor at the University of Rochester.
The Conversation's article is a Creative Commons licensed one. The original article can be found here.
