Brain's Memory More Powerful Than Thought
You don’t have a limited memory that can be used up. The only limits are on how much you desire to know.
A new PNAS paper by psychologists from Harvard and the University of California at San Diego has an instructive title: “Working memory is not fixed-capacity: More active storage capacity for real-world objects than for simple stimuli” by Brady, Stormer and Alvarez. Unlike computers, which have fixed registers and RAM, the human brain seems to have almost limitless capacity for short-term memory (the kind you use when actively observing and thinking, as opposed to long-term storage). Here’s the significance of their findings:
Visual working memory is the cognitive system that holds visual information in an active state, making it available for cognitive processing and protecting it against interference. Here, we demonstrate that visual working memory has a greater capacity than previously measured. In particular, we use EEG to show that, contrary to existing theories, enhanced performance with real-world objects relative to simple stimuli in short-term memory tasks is reflected in active storage in working memory and is not entirely due to the independent usage of episodic long-term memory systems. These data demonstrate that working memory and its capacity limitations are dependent upon our knowledge. Thus, working memory is not fixed-capacity; instead, its capacity is dependent on exactly what is being remembered.
Visual working memory has limits, of course; it’s often used as a measure of intelligence. Most people struggle remembering 3 or 4 unfamiliar visual objects at a time when they are undergoing changes. When remembering familiar objects, though, people generally remember more for longer times. The researchers decided to look further into the reasons for the difference.
After running experiments with participants at Harvard asked to recall unfamiliar objects or colors compared to real-world objects, they psychologists change the paradigm about memory limits. “Overall,” they conclude, “this suggests that visual working memory does not always comprise the fixed capacity previously described based on studies using simple stimuli but is a flexible system that varies in capacity depending on stimulus type.”
Working memory, furthermore, interacts with long-term storage so that no capacity limit is reached when remembering real-world objects. The experiments suggested that “participants are maintaining active working memory representations of the objects and are also forming episodic long-term memory representations that will be available even after a significant delay.” The different regions of the brain are all sharing information with each other.
In addition to all this, working memory stores more information about objects than just color. Counter-intuitively, the capacity to remember simple objects, like colored polygons, is not as good as remembering detailed, complex objects that carry conceptual meaning. Images of teapots, donuts and butterflies, for instance, were easier to recall than unfamiliar geometric shapes or colored squares.
This idea is consistent with evidence suggesting that the brain regions involved in processing perceptual representations of different stimulus categories contain information about which items are in memory. Thus, one possibility for why participants can actively store more information in visual working memory for real-world objects than for simple color stimuli is that a wider variety of long-term memory representations and perceptual representations are relevant and can be refreshed for real-world objects than for simple stimuli. This may reduce interference and allow for more information to be remembered.
If there was any “survival value” or “selection pressure” for the emergence of this capability, the authors didn’t say so. In fact, they didn’t mention evolution at all. Their conclusions are consistent, instead, with intelligent design:
By measuring active storage using the CDA [contralateral-delay activity], we found that working memory accumulates information over a greater time scale for real-world objects than has been shown for simple colors and that more real-world objects than simple colors can be stored in working memory. These results demonstrate that working memory capacity is systematically underestimated by using simple stimuli about which we have no existing knowledge. Our findings also raise important questions about the functional role of the visual working memory system. In particular, they raise doubts that the entire function of visual working memory can be to persist information across eye movements, because the system seems to continue to accumulate information on a much longer time scale than typical fixation durations.
From our uniform experience, “systems” that “accumulate information” for a “functional role” are intelligently designed. The design of the memory “system” was underestimated by scientists posing the wrong questions.
For more on how memory works, see Nature Communications about the hippocampus as a “convergence zone, binding different aspects of an episode into a coherent representation, by integrating information from multiple brain regions.” Compare this with the unusual story of a woman with amnesia whose hippocampus was disrupted (Medical Xpress). Her experience “defies conventional wisdom” about memory. And in another story on Medical Xpress, Michy Kelly discusses the mechanisms of memory, particularly her discovery of “PDE11A—a protein enzyme no one thought was even located in the brain—and its importance to social memory.”
Here’s another example of biological research that had no need for Charlie’s myths. The operative terms were system, function, and information. Why would blind processes of chance produce an almost unlimited capacity to learn and remember things? The more you learn, the more capacity to learn. A mind is too beautiful a thing to waste.
Remember this paper when facing the real world. Darwin’s Stuff Happens Law is not useful, but design is. Meaningless evolutionary just-so stories, no matter how colorful, deserve to be dropped from memory and replaced by real-world concepts containing useful information. You have more capacity for storing useful information than scientists believed. Don’t let it stand idle. Fill it up! Paul said, “whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things” (Philippians 4:8).