Understanding and Curing Myopic Voting

The abstract from a recent talk by Gabriel Lenz of MIT:

Retrospective voting is central to theorizing about democracy. Given voters’ ignorance about politics and public policy, some argue that it is democracy's best defense. This defense, however, assumes citizens are competent evaluators of incumbent politicians' performance. Although little research has investigated this assumption, voters' retrospective assessments in a key domain, the economy, appear flawed. They overweight election-year income growth in presidential elections, ignoring cumulative growth under the incumbent. In this paper, I present evidence that this myopia arises from a more general “end bias” in retrospective assessments. Using a three-year panel survey, I show that citizens' memories of the past economy are inconsistent with their actual experience of the economy as they reported it in earlier interviews. They fail to remember the past correctly in part because the present shapes their perceptions of the past. I then show similar behavior in the lab. When participants evaluate economic and crime data, I again find that election-year performance shapes perceptions of overall performance, even under conditions where the election year should not be more informative. Finally, I search for and appear to find a cure. Presenting participants with cumulative information on performance (e.g., total income growth or total rise in murders during incumbents’ terms) cures this myopia. On one hand, these results are troubling for democracy because they confirm citizens’ incompetence at retrospection. On the other hand, they point to a remedy, one that candidates and the news media could adopt.

That's a remedy as long as the candidates and news media don't simply lie about the fact. Good luck with that one.

How many memories fit in your brain? More than we thought

One of the most obvious facts about memory is that it is not nearly so good as we would like. This definitely seems true in day-to-day life, and one focus of my research during the last couple years has been why our ability to remember what we see over even very short time periods is so very limited.

So memory is crap, right?

It may be hard to remember a visual scene over a very short time period, but new evidence suggests that it is remarkably easy to remember a visual image over a longer period of time (several hours).

Researchers at MIT showed participants nearly 3,000 visual images (see some of them here) over the course of 5 1/2 hours. Afterwards, their memory was tested. They were able to discriminate the pictures they actually saw from slightly altered versions of the same picture nearly 90% of the time.

This is frankly incredible. When I show participants much, much simpler images and then ask them to recognize the same images just 1 second later, accuracy is closer to 80%!

These results are going to necessitate some re-thinking the literature. It suggests that our brains are storing a lot more information than many of us thought just a little while ago. It also suggests a very strange interaction between time and memory strength that will need to be better understood.

So this is a surprise?

Yes, and no. The results are surprising, but their publication last week in the Proceedings of the National Academy of Sciences was not, at least not for me. I had the opportunity to first be stunned by these data nearly a year ago, when the third author gave a talk at Harvard. It came up again when he gave another talk during the winter. (Oh, and I've known the first author since we sat next to each other during a graduate school application event at MIT, and we still regularly talk about visual memory).

So I and many others have had the opportunity to think through the implications for a long time now, which means it is very possible that there are labs which have already completed follow-up studies.

While this has nothing to do with the big story itself -- the sheer massiveness of visual memory elicited in this study -- I bring it up as an example of my point from last week: the fact that America is (for now) the center of the scientific world gives us tremendous institutional advantages, the least of which is that it is much easier to stay fully up-to-date. If that mantle passes to another country, we will be the ones reading about old news only when it finally comes out in press.

Parting Thoughts

If you yourself have done research like this, the first thing you probably wondered was where they got 3,000 carefully controlled visual images, not to mention all the test images.

Google Images, baby, Google Images. It still took a great deal of time, but as I hear the story told, the ability to download huge numbers of web images via Google was immensely helpful. This is just one more example of Web search as a tool for science.

Interference in Memory

I wrote recently about interference processes that cause memory failure. As I wrote before, retroactive interference is when learning new information causes you to forget what you learned previously. In proactive interference, old information makes it hard to learn new information.

It turns out that there are (maybe) two types of proactive interference, and this may tell us a great deal about how memory works.

How Specific?

Half a century ago, Keppel & Underwood found that people quickly get worse at memory tasks. A basic task works like this: Remember the following letters: "etnmwo"

Now look away from the screen. After a few seconds, ask yourself what the letters were. How many could you remember?

Keppel & Underwood task was slightly different, but this gives you the basic idea. Again, what they found was that as people play this game, they actually do best on the first trial, worse on the 2nd, even worse on the 3rd, etc. (People bottom out fairly quickly, as we'll see in a future post.)

Keppel & Underwood suggested that this was due to proactive interference, which now seems pretty well established.

Later researchers discovered a curious thing. If the memory task is done with letters for a while, and then the experimenter switches to numbers, the participants suddenly get better. It doesn't have to just be letters and numbers. Switching from one type of item (say, names of car manufacturers) to another type (say, names of animal species) typically leads to an improvement in performance.

This has been called "release from proactive interference." But it is not the only kind.

More Specific

The type of proactive interference discussed above has been called "item-nonspecific" proactive interference. Learning information about one item made it harder to remember information about similar items.

This can be contrasted with "item-specific" proactive interference. As an example, go back to the sample memory test above. You were asked to remember "etnmwo." Suppose in the next trial, I asked you to remember "oaqzp" for a few seconds, after which I asked you:

"Is one of the letters are are supposed to remember an E?"

There is a decent chance you would incorrectly say "yes." This is because, although E was not one of the letters on this trial, it was one of the letters on the previous one. If I had instead asked about the letter C, which was not in either trial, you would be more likely to respond correctly and say "No."

This effect was discovered by Monsell using what is called the "Recent Probes Paradigm" -- which is basically what I just described.

Two Types or One?

One could legitimately wonder if these are really two different phenomena. That is, maybe item-specific proactive interference is simply a stronger version of item-nonspecific proactive interference.

It is hard to answer that question using behavioral experiments. Luckily, this is one of those places where neuroimaging can be helpful in understanding behavior. Recent neuroimaging results have found a strong overlap between the brain regions involved in the two types of proactive interference.

What Does this Say about Models of Memory?

Jonides and colleagues have been developing a model of memory that may both describe and predict the data on proactive interference.

In the model, to the extent that I understand it, you perform a short-term memory task like the ones described above by activating representations of the items. That is, to remember "aort," you would activate your long-term memory representations of A, O, R & T. But you do not actually hold those representations in consciousness; it is more that you make them easy to retrieve.

Now, suppose I ask you to repeat back those letters. You have to retrieve each of the four letters into consciousness so that you can give me your answer. You do this via something vaguely akin to a keyword search. That is, you search your memory for relevant features (e.g., a letter, recently encountered, seen on a blog, etc.). Since A, O, R & T all match those features and are all activated in memory, you retrieve them successfully.

Suppose on the next trial, though, you have to remember W, Z, P & E. So you activate those representations in memory. But A, O, R & T also remain somewhat active. And they also match most of the features (i.e., "keywords"). So you might accidentally retrieve one of them (item-specific proactive interference). In addition, since memories overlap, the still-active A, O, R & T representations make it harder to activate and maintain the representations of W, Z, P & E, since the compete for use of some of the same neurons. This might just make you fail to activate or retrieve anything at all.

Notice that if on the next trial, I ask you to remember 9, 3, 5, & 2, these items share fewer features with the letters on the previous trials, making the "keyword search" easier. Also, the representations of 9, 3, 5 & 2 in the brain are more distinct from the representations of the letters in trials one and two than either were from each other. Thus, you get release from item-nonspecific proactive interference.

Monsell, S. (1978). Recency, immediate recognition memory, and reaction time. Cognitive Psychology, 10(4), 465-501.

Keppel, G., Underwood, B.J. (1962). Proactive inhibition in short-term retention of single items. Journal of Verbal Learning & Verbal Behavior, 1, 153-161.

Jonides, J., Lewis, R.L., Nee, D.E., Lustig, C.A., Berman, M.G. (2008). The mind and brain of short-term memory. Annual Review of Psychology, 59, 193-224.

Forgetting what you haven't yet learned

More than one student has complained that the space in their head is limited, and new information is simply pushing the old information out. In the terms of memory research, this is retroactive interference: learning new information causes you to forget old information.

The way this is typically studied in the laboratory is to have the participant learn something -- often a paired associate (think "Concentration") -- then learn something else, and then finally be tested on the original memory item(s). This way, one can vary that middle task in order to study how different activities cause different amounts/types of retroactive interference.

The is another type of interference: proactive interference. This is the effect that learning one piece of information has on future learning. That is, the books a student has already read make it harder to learn new information.

Just like retroactive interference, proactive interference is seen in both short-term and long-term memory. 

Memory Systems: How Does Memory Work?

The existence of interference tells us a lot about how memory works, because there is nothing necessary about it.

Consider a computer. We don't expect each new file we add to our computer to cause the computer to lose other files, short of copying over those original files. Similarly, the file I added today should not affect a file I add tomorrow, short of causing me to run out of disk space.

So why is human memory affected this way?

Overlapping Memories

There are a couple reasons it could be. One is that memory is probably overlapping. A computer -- at least, in its basic forms -- saves each file in a unique place in memory. The human brain, however, probably reuses the same units for different memories. Memories are overlapping.

How exactly this works is still very much a matter of research and debate, but it makes a certain amount of sense. Suppose you have several different memories about your mother. It would make sense for your mental representation of your mother to show up in each of those memories. For one thing, that should make it easier to relate those memories to one another.

Searching for Memories

Another way interference might appear in memory is in how it effects memory retrieval. The more files you put on your computer, the harder it is to find the files you want. This is especially true if you keep them all in one directory and use keyword searches.

Human memory retrieval probably does not work like a keyword search, but nonetheless it is reasonable to assume that the more memories you have, the more similar memories you have. Thus, finding the right memory is harder, because you have to distinguish it from similar memories.

How exactly this plays out depends on your model of memory. I will talk about one I particularly like in a future post.

Upcoming Posts

Although  my main research is in semantics and pragmatics -- aspects of language -- I have also worked on working memory. I have a paper coming out shortly based partly on an experiment I ran at my Web-based lab. Over the next week or two, I plan to write about some of the fundamental questions about memory addressed in that paper, as well as write about the paper and lay out its results.