She's Got That Knowing Feeling
How Metal-Detecting is Like Recalling Memories
The Feeling Of Knowing Is Like Metal Detecting
If you’re like me—old, with a failing memory—when someone asks you who was the boss on Who’s The Boss, you probably know that you know the answer before you can say it.1
This feeling that the answer you’re looking for is in there somewhere, the tip-of-your-tongue phenomenon, is called the “feeling of knowing.”
Keeping with my ongoing mission to explain what every human feeling is measuring and motivating, this piece is a meditation on the feeling of knowing. To get at it, I’m going to draw an analogy between this feeling and metal detecting. Yes, I mean that thing you see people doing on the beach. I’m going to argue that some similar principles are at play.
I have been reading a fascinating Substack on metal detecting, which includes stories about finds as well as tips and information about the tools of the trade. Highly recommend.
Here are a few things about metal detecting. First, metal detecting is like bartending in the sense that to me it would seem natural to say “I’m tending bar,” but, instead, bartenders always say “I’m bartending.” People who detect metal always say they are metal-detecting but they never say they are “detecting metal.”
Ok, more to the point, it turns out that when one detects metal, there are really three devices at work.
The first one is the metal detector, the rod-shaped device that tells you if there is something—gold, iron, etc.—in the area under its sensor. The output can be visual—on a screen—or audio—to headphones. The second device is called a pinpointer. It can’t scan as large an area as the metal detector, but, true to its name, it pinpoints where the metal is. This device trades area of search for specificity. The last device is the user’s senses, usually the eyes.
When you’re metal-detecting, the key question is whether to stay on the present patch or to move on. Staying on the present patch only makes sense if there is reason to stay. Otherwise, staying carries the opportunity cost of searching other areas. This is a direct analog of how behavioral ecologists think about search when it comes to animals foraging for food. The signals that one gets from one’s metal detector can be thought of as indicating the probability that there is something there.
Now, as you’ll learn when you read Detector’s Digest, there are sometimes false positives—the device produces a signal but there’s no find. This is common for all signal detection problems. There are always errors, in both directions.
Foraging in Memory
Hunting for a memory is like hunting for metal.
When you are searching for a memory, there are opportunity costs. Opportunity costs are simply the benefit one forgoes—the benefit one could have gotten—when one makes a choice. So the cost of metal-detecting in Valley Forge National Park might be your next best option, metal-detecting in the Wissahickon creek. (Today’s post is very Pennsylvania centric.) More narrowly, staying on a patch comes at the price of looking in the next patch.
Analogously, time spent trying to remember the name of the television star carries a time cost: specifically, the time that can’t be spent trying to remember something else or, more generally, using one’s limited attention and cognitive cycles to do something else useful or fun. The trick, then, is to continue one’s search for information in memory only if the benefit of doing so—which depends on the probability the searched-for item will be found—outweighs this cost.
The feeling of knowing is a measurement of this probability. When the probability is high—we feel like we will eventually be able to recall the information—we are motivated to continue to search our memory. So there are (at least) two representations in there somewhere: one, the likelihood that we know the information, and two, the information itself.
I confess that I am not an expert in this area, but there is a corollary. It seems to me that humans also experience the reverse, a feeling of not knowing. When I am at quizzo with my team, I get this feeling as soon as the quiz master says something like, “In the 2008 Stanley Cup Final…” The feeling is that there is no chance, at all, that I have the required information feels distinct to me and it’s useful. As soon as the NHL comes up, I can stop listening and go back to eating my nachos. This feeling motivates abandoning the search because the opportunity costs outweigh the expected benefits.
What about other tasks besides recall?
There’s a similar feeling for problem solving and related tasks. If you ask people if they could memorize a list of fifty words, they know that they can’t do it. This wisdom, by the way, only comes with age. Classic work in developmental psychology2 showed that if you ask young children to predict how many items on a list they will be able to remember, they are extremely bad at it, often absurdly optimistic. The feeling-of-knowing-if-I’ll-be-able-to-do-this-task is useful, again, to allocate your cycles effectively.
In this way, memory search—and problem solving—are like metal detecting and foraging. There is some signal—video, audio, or phenomenological—that measures the likelihood of a benefit to continuing working on it. While that measurement is high, the search continues. When it is absent, it’s time to move on.
Birds, Birds, Birds
You can demonstrate this feeling for yourself, if you’re so inclined.
Suppose you want to think of as many different birds as possible. Start with a category such as “birds of prey.” You’ll probably come up with eagle, hawk, falcon, and, if you know a lot of birds, maybe next will be osprey or kestrel… if you’re very, very knowledgeable about birds, you might come up with birds within those categories, such as Bald Eagle, Red-tailed Hawk, and so forth. (Can you tell my partner is into bird-watching?)
Anyway, as you work through the list of raptors, it’ll feel harder to come up with the next one. There are, as economists say, diminishing returns to your efforts. The reason is that you know only a certain number of birds of prey and some are easier to recall than others. (Bald eagle comes to mind very easily for me; I had to stretch for osprey.) Once you’ve gotten the easy ones, well, the next ones are, by definition, harder. And somehow you know this. There is some little program running in your brain whose job it is to figure out how difficult it is going to be—how much time it will take and the likelihood of eventual success—to recall the next bird. My guess is that this feeling of effort is similar to the feeling that a bear gets when it has gotten all the berries that are easy to get so that the value of staying at that berry bush is low relative to the benefit of moving to a new patch.3 In that case, a good way to figure this out is to measure the time between harvesting berries, which will go up as more low-hanging berries are harvested. Maybe a similar process is at work for memory.
Ok, the next “patch” of birds is “species found in a zoo.” Go.
You should now quickly be able to generate another bird—probably an ostrich, maybe a peacock, emu, or black swan. This move to another memory patch is like moving to a fresh new berry bush: there are now some low hanging birds to pluck from your memory, to strain the metaphor to its breaking point.
You can keep adding to your bird list relatively easily by first thinking about bird categories—perhaps birds that you keep as pets, African birds, etc.—and you’ll be able to come up with a new bird because you haven’t yet depleted that patch.
My sense, for what it’s worth, some software works this way. If you are writing code that matches people who need a lift with people who have a car, then you need some way to stop the search if there are no more drivers available. I don’t know exactly how Uber or Lyft work in this respect, but, from having visited some pretty sparse locations—looking at you, Scranton—after a certain amount of time the app times out and admits there aren’t any cars around. Generally, routines that time out—exit once a certain amount of time has passed—illustrate the same functional structure. There is a variable in there somewhere that is keeping track of the amount of time that has elapsed since the search began. This is parallel to whatever is going on in our heads.
Summary
In sum, there are two phenomena here.
The tip-of-the-tongue feeling is evolution’s way of telling you to keep going. Somehow, the system knows that the information you’re looking for is in there somewhere, so it pays to continue looking. What is being measured is something like the probability I’ll be able to recall the needed item and what is being motivated is continuing the search.
The sense of effort in the bird task is the reverse, evolution’s way of telling you that it’s time to stop what you’re up to and move on to the next patch. Again, the measurement is the speed with which the next bird will fly into memory and the motivation is to exit search.
These feelings—go signals and stop signals—are crucial because everything we do—and think—comes with costs. It’s fitness-good to continue only if the benefit of continuing outweighs the cost. And there is always a cost because there is always something else you might be thinking about.
Coda.
Happy holidays and new year to all! (If you would like to give the Living Fossils a gift to say thanks for the great articles this pas year, ask your friends to subscribe😊.)
REFERENCES
Flavell, J. H. (1970). Developmental studies of mediated memory. Advances in child development and behavior, 5, 181-211.
Hills, T. (2006). Animal foraging and the evolution of goal directed cognition. Cognitive Science, 30, 3-41.
Hills, T. T., Jones, M. N., & Todd, P. M. (2012). Optimal foraging in semantic memory. Psychological review, 119(2), 431.
Hills, T. T., Todd, P. M., & Jones, M. N. (2015). Foraging in semantic fields: How we search through memory. Topics in cognitive science, 7(3), 513-534.
Tony Danza.
Flavell, 1970
See Hills, Jones, & Todd, 2012 and Hills, Todd & Jones, 2015, for some experimental work on this.
Nice post. I sometimes keep going past the point when opportunity costs would tell me to stop, partly because I am terrier-like and partly because once one memory escapes me I fear all the others will see I'm no longer the hunter I once was and start playing hide-and-seek, just for the hell of it.
What would you say 'Proustian moments' are measuring and motivating and why do they feel profound?