Negative Emotions and Memory

I have a big section in my memory book on the interference with memory formation caused by negative emotions. I have seen first hand how emotional crises cause the grades of college students to plummet. Whenever a good student suddenly starts making poor grades, I know this student has recently had an emotional trauma. Common problems for college students include trouble making friends, boy/girl problems, parent divorce, homesickness, financial worries―grades invariably suffer.

Recently, I had a reader of this blog challenge my position, pointing out that the most severe form of negative emotions, post-traumatic stress (PTSD), has as its main problem the inability to forget the events that triggered the PTSD. My reader is of course correct. But so also is all the evidence that negative emotions interfere with memory. How do I reconcile these incompatible views?

What is so well-remembered in PTSD are the traumatic events that caused the negative emotions. That is not the same as saying that PTSD patients have exceptional ability to remember other things or learn new things. I contend that their memory for new learning is impaired because of their distressed emotional state. The reason they remember the PTSD events so well is because they rehearse them so often.

All intense situations, even happy ones, tend to be well-remembered because of the intensity of the stimuli and the fact that such situations are repeatedly rehearsed. Rehearsal usually occurs immediately, because of the intensity of stimulation, and is repeated frequently, because the situation had such a big emotional impact. It is not so much the positive or negative aspect of the situation that matters for memory formation, but rather the timing and frequency of rehearsal.

Why do negative emotions interfere with new learning? I haven’t seen formal studies of this question, but what I know about memory allows some useful speculation. First, feelings such as worry, fear, depression, loneliness, and the like, have devastating effects on motivation. Under such conditions, nobody feels much like taking on challenges. Negative feelings also make it hard to pay attention to anything else besides what is causing the emotional distress. Attentiveness is pre-requisite for forming memories of new learning. Negative feelings lead to persistent negative thoughts, and thinking about one thing while trying to memorize another just doesn’t work. Negative feelings also erode confidence and sense of well being, both of which are essential for optimal memory ability. Why confidence and sense of well being are important is unclear, but I suspect they motivate a person to do what it takes to achieve personal goals. In the case of memory ability, it is easier for an up-beat person to take on learning challenges and to do the right things for promoting memory formation.

Reading comprehension: role of eye movements

The capacity of working memory, for example the number of digits in a phone number you can hold long enough to dial it, determines how well you can think and the ability to form lasting memory. I have explained this in my book, Thank You Brain For All You Remember. New insight into working memory capacity has recently been reported by Paul Bays and Masud Husain in a research report in Science. They studied the capacity for visual memory, that is, the number of visual objects a person can hold in working memory. In the study, the emphasis was on the role played by eye fixation.

The design was to display four geometric shapes on a screen, each with a different color. The subjects viewed the screen without moving their eyes, and then the screen was blanked. Next, one of the items was redisplayed, but in a different location and rotation. The working memory task was to remember the original orientation and location. The objects were then withdrawn. Typically, subjects recalled well as long as the set size was no larger than four and as long as the probe object was not changed much. But precision of recall fell off drastically, even with only two or three objects, if the probe object was moved significantly.

Next, they wanted to explore the effects of moving the eyes across the stimulus field. Actually, this presents a major challenge to the brain, because more information has to be held in working memory. Even so, the results when eye movement was allowed and when it was not seemed about the same. The decline in accuracy depended mostly on the number of objects in the set. This suggests that the brain parcels out the task so that memory resources are assigned proportionately to each item. But eye movements are important. In another study, subjects made a series of eye movements to fixate on each item in a five-set display, and the screen was blanked just before the fifth item was fixated. Then subjects were tested to report the location and orientation of the objects. Accuracy was greatest for the fifth item, presumably because the brain had allocated more of its memory resources to registering the item the eyes were about to fixate. This, of course, is being done at the expense of remembering all of the previous four fixations.

These facts must have profound implications for reading comprehension. Certainly, these data seem to support the value of “whole reading” theory, which emphasizes fixing eyes on whole words, preferably where one eye fixation takes in several words.^* The point is that if brain allocates more of its memory resources to each upcoming eye fixation, then reducing the number of fixations ought to increase comprehension, as indicated by working memory of what is seen with each fixation. In other words, the brain can process the meaning of multiple words in an upcoming fixation because the brain is devoting more memory resources to the next fixation task.

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^*This is not to denigrate phonics, for there is compelling evidence that phonics is the best way to learn words in the first place. But once learned, remembering the words you read is probably best achieved by reducing the number of eye fixations.

Source:

Bays, P. M., and Husain, M. 2008. Dynamic shifts of limited working memory resources in human vision. Science. 321: 851-85

New Neurons Die Unless You Save Them

A recent study in adult mice indicates that new neurons in the memory-forming part of the brain have only a narrow time window, about three weeks, in which they can be saved. How were the saved from death? ... by providing a stimulating environment. Rather than being raised in standard laboratory cages as were the controls, the test mice lived in groups in cages that had various toys and things to do. These neurons survived if they were born one-to-three weeks earlier, but not if the enriched environment was available later.The spared neurons survived throughout the four-month observation period.

People also presumably are birthing new neurons, but learning experiences and mental activity are probably needed to help these new neurons to get incorporated into existing circuitry. If new neurons don't get included in circuitry, they will die.

For more details, click here.
To get the big picture of how memory works and how to improve it, get the book. Click here.