Memory and VARK Part 1: Sensory Memory

Along with Sperry’s work on split-brains, the VARK theorists also list Alan Baddeley’s work on memory in their bibliography. No direct citation is provided for his work, so I cannot be sure what exactly is cited from it. After reviewing the source, I had found a handful of places where Baddeley discusses the processing of different senses/sensory modalities. In this series of posts, I will review those discussions and try to infer what is relevant to VARK (or other theory of learning modality preference) studies.

There are four different places in Baddeley’s 1984 book where he discusses modality differences in memory. They are:

1.      sensory memory
2.      encoding of memories
3.      semantic memories
4.      working memory

In this post, I will focus on sensory memory.

Sensory memory is the idea that most of what you experience through your senses is temporarily stored in a memory system that allows you to access it. The vast majority of information is lost from this system, but some of it is attended to and passed on to short-term and then long-term memory. Here is a quick illustration of the three main systems/types of memory and the way they interact (Atkinson & Shiffrin, 1968).

The existence of sensory memory was shown experimentally by George Sperling in 1960. Sperling presented subjects with 3 x 3 matrices of letters and asked them to recall (freely) as many as possible. Most subjects could recall 4-5 letters at a time. This result was fairly well known at the time and was nothing new. Sperling tweaked the experiment and had the subjects perform a cued recall. Following the presentation of the 3 x 3 matrix of letters, a second screen was presented with one location of the 3 x 3 matrix cued. Subjects were supposed to remember the specific letter that corresponded to cued location. Surprisingly, subjects were quite good at this. According to Sperling, the entire visual field had been placed into sensory memory and so any of it could be remembered via a cue. If you just ask subjects to recall freely (with no cue), they cannot remember all of the letters because by the time they have remembered a few of them, their sensory memory of the other letters has disappeared.

In his book, Baddeley discusses the existence of a visual sensory memory (called an iconic memory) and of an auditory sensory memory (called an echoic memory). This is the first place in the book where I found information related to different sensory modalities. Iconic and echoic memory systems are focused on different modalities (visual and auditory, respectively). Does the existence of these memory systems provide evidence in support of VARK? Well, VARK theories depend on individual differences in modality abilities. They believe that some people are better visually and other aurally. Is there any evidence to support this notion from the discussion of sensory memory in Baddeley’s book?

In short, no.

Baddeley (1984) has no discussion of whether individual differences occur between iconic and echoic memory systems. Baddeley does discuss differences between these systems, but suggests that these differences are more universal:

“The existence of a rather more durable auditory memory system can be shown as follows. Suppose I were to read out to you a series of nine-figure telephone numbers, The chances are that you would get most figures of each number right, but would tend to make errors. If I then switched to a system of presenting the numbers visually, one figure at a time, you would find that you made rather more errors, particularly towards the end of the sequence…. A sequence of spoken numbers is better remembered than a sequence of numbers presented visually because auditory sensory memory appears to be more durable that visual.”

From Baddeley (1984). The number of errors made is graphed above. The dark curve is for iconic memory and the light curve is for echoic memory. As you can see, people make more errors in iconic (vsual) memory towards the end of a sequence compared to echoic (auditory) memory.

To be completely honest, there is one place in his discussion of sensory memory where Baddeley mentions some individual differences. He discusses the length of time that subjects are able to hold something in auditory sensory memory and says: “…subjects vary somewhat in their capabilities, but on average can detect repetitions separated by up to three seconds, indicating an auditory memory system of at least this duration.”

Is this brief mention of individual differences in echoic memory evidence for VARK theories? I don’t believe so. Baddeley is saying that some people have longer temporal capacities for their echoic memories, but he does not discuss that the iconic memory system may compensate for this in some patients. For these data to support VARK theories, some subjects would have to demonstrate better iconic memories than echoic memories and vice versa. Instead, according to Baddeley, we universally see a more “durable” auditory sensory memory system compared to visual sensory memory. We just see slight differences in the capabilities of everyone’s auditory sensory memory.

References

Atkinson, R. C., & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes. In K. W. Spence (Ed.), The psychology of learning and motivation: Advances in research and theory (Vol. 2) (pp. 89-195). New York: Academic Press.

Baddeley, A. (1984). Your Memory: A User’s Guide, England: Penguin.

Sperling, George (1960). "The information available in brief visual presentations". Psychological Monographs 74: 1–29.

Calling all left brains

Reviewing the sources for Fleming’s VARK model took me to the Roger Sperry (1973) article first. My first goal was to try to figure out why VARK theorists (such as Neil Fleming) cite Sperry’s work. In the VARK literature, I could find one article that explicitly cites Sperry’s work (Fleming and Mills, 1992). Here is the quote:


“By questioning students, we found that many students attributed their learning difficulties to the form in which course material was presented. Some students found they had difficulties learning in situations where the course material was only presented orally, while others reported similar difficulties when the material was primarily in written form. Still other students experienced difficulty with ideas that were presented in graphics or 'without any associated concrete experiences.’ These insights prompted us to focus on sensory modality as a learning style dimension that had some preeminence over others. The notion that the way information is initially taken in by a learner influences what subsequently occurs has intuitive appeal.


“We found support for this notion in literature on neuro-linguistic programming (NLP) (Handler, 1976, 1979; McLeod, 1990; Stirling, 1987) that discussed the different perceptual modalities (aural, visual, and kinesthetic). The following questions were suggested from our exploration of this field of study, split-brain research (Gazzaniga, 1973; Sperry, 1973; Springer & Deutsch, 1985) and left brain/right brain modalities (Buzan, 1991; Edwards,1979):


1. How can students be encouraged to reflect on the nature, extent and implications of their sensory modalities?


2. As a consequence of exploring their sensory modality preference, will students modify their existing learning strategies in ways that assist their learning?”


Unfortunately, this citation tells me little about what they find relevant from the Sperry article. With little guidance from their citation, I had to go in search of what might be relevant in the field of split brain research to VARK myself.


It wasn’t hard to find what VARK theorists found relevant from Sperry’s work. In the first paragraph of his article, Sperry claims “…our education system, as well as science in general, tends to neglect the nonverbal form of intellect. What it comes down to is that modern society discriminates against the right hemisphere.” While this quote might be relevant to VARK’s idea that various learning modalities are not addressed the way they should be, this is the only mention of this idea in the entire Sperry article. The remainder of the article is a scientific review of split brain research that had been completed up until 1973. Let’s explore Sperry’s ideas and work a bit more to see if we can find any other evidence that could be used to support the VARK theory.


To give you a little background, Roger Sperry started his career by studying hemispheric specialization in cats. In a landmark study at CalTech, he examined cats that had been given a split brain. We know that the brain has two halves (hemispheres). Normally, the two hemispheres are connected (by a structure known as the corpus callosum), and information that the right side gets is readily shared with the left side and vice versa. However, Sperry found that if the corpus callosum is severed (aka split-brain), one side of the brain can learn something and the other side can be oblivious to this.


In his experiment with cats, Sperry presented one half of the cat’s brain with a maze to learn and navigate. He did this by covering one eye of the cat and thus only information from the uncovered eye went into the brain. He had cut the optic chiasm which kept the information from each eye separated to its own side of the brain. In other words, information from the right eye went only to the right hemisphere and information from the left eye went only to the left hemisphere.


Sperry taught one side of the cat’s brain how to navigate a maze. Then he changed the eye that was covered and showed that while one side had learned the maze, the other side of the cat’s brain had learned nothing. The second side could be taught how to navigate the maze as well, but had to be taught separately from the first side. This experiment showed that the two halves of the brain can operate independently. Sperry was even able to change the specifics to the learning experiment so the two halves of the brain learned opposite things (Sperry, 1961). Cool, huh?


As with any good science, these findings lead to many questions. Since Sperry’s work suggested that the two halves of the brain can operate independently, how complete are the operational capabilities for one hemisphere of the brain? Could both halves of the brain speak, read, write, add, subtract, grab, remember, etc? Or does each hemisphere need the other to be able to function properly?


To answer these questions let’s fast forward to the work that was cited in the VARK paper. Sperry (1973) is a review of work (mostly in humans) about hemispheric specialization (ie what each half of the brain is capable of doing). Sperry offers the following answer to the question posed above:


“A long series of studies indicate that the two disconnected hemispheres function independently and in effect have each a separate mind of its own. Each of the separated hemispheres appears to have its own private sensations, perceptions, thoughts, feelings, and memories. Each hemisphere has its own inner visual world, each cut off from the conscious awareness of the other.”


He describes patients that have surgically had their corpus callosum cut. This procedure is done as a treatment for extreme cases of epilepsy with very positive results. But what about the side effects of this operation? Sure their epilepsy may be controlled, but at what cost. Can they still function without their two hemispheres connected and communicating?


The answer is surprising to many. Sperry explains it well: “The behavioral symptoms produced by severance of these enormous systems of fiber cross-connections are found first of all to be surprisingly inconspicuous in ordinary behavior. The hemispheres continue to function in the separated state at a fairly high level such that a person two years recovered and otherwise in good condition could easily go through a routine medical checkup without revealing that anything was particularly wrong.” That is, there are no noticeable deficits in split brain humans. How can this be explained? From above, it is stated that the two hemispheres can operate independently. If they are cut and operating independently, wouldn’t there be some sort of sign of this? One might reasonably expect that the two hemispheres would disagree periodically and show conflicting behaviors, right?


That is not what we see in the vast majority of these patients (except in extreme cases where alien hand syndrome develops- you should google that one if you are interested). What does happen though is that in most patients one hemisphere seems to become dominant over the other. Interestingly, there is a pattern to which hemisphere takes over; it is usually the left hemisphere. Researchers believe that this is because the left hemisphere has language abilities and the right hemisphere does not. Since the world around us requires language to a large extent, the thoughts and processes of the language hemisphere appear to be dominantly expressed. I found the following quote quite interesting: “The disconnected minor hemisphere, lacking language like the animal brain and thus unable to communicate what it is thinking or experiencing, is much less accessible to investigation, and accordingly the nature and quality of the inner mental life of the silent right hemisphere have remained relatively obscure. There is reluctance in some quarters to credit the minor hemisphere even with being conscious, the contention being that it is carried along in a reflex, trance-like state, with consciousness centered over in the dominant left hemisphere.”


Here is a great youtube video on split brain studies and left vs right hemisphere differences.

Let’s try to bring this back to VARK. Sperry makes the argument that the left hemisphere does certain tasks and the right hemisphere does others. He suggests in the beginning of the article that the tasks that are typically “right hemisphere” tasks are ignored or discounted in our current education system and in society. From what I can tell, the learning style (in this case VARK) theorists liked this particular idea.


Let’s get into Sperry’s discussion a little more. Sperry makes the point that the right hemisphere is not without its strengths. To quote Sperry: “From its nonverbal responses we infer that the minor hemisphere senses, perceives, thinks and feels all at a characteristically human level, and that it learns and remembers and has some reasoning capacity and considerable perceptual insight that is superior to that of the major hemisphere for certain things. Also that it may even do some silent reading of object names and some drawing, not to mention various things that we have not yet tested.”


The right hemisphere appeared better at block designs, drawing figures, and other spatial tasks (such as transforming a 3D figure into a 2D representation). This increase in performance is found when the stimuli are presented visually or when the stimuli are given to the left hand to touch (the left hand is controlled by the right hemisphere of the brain).


According to Sperry, “The right hemisphere excelled in acquiring concepts that involved spatial qualities like height, size, shape, and the left excelled when the concepts involved familiar objects with distinctions that were easily verbalized.” Sperry even discusses one manipulation where subjects were presented words written in cursive. If subjects were asked about the meaning of the word, the left hemisphere was far superior. When subjects were required to match the visual look of the word to another stimulus, the right hemisphere was found to be superior.


There do seem to be exceptions to the “left dominant” pattern that is typical in most patients. Sperry discusses finding some patients that have developed language bilaterally (in both hemispheres). Sperry claims that if both “verbal and nonverbal perceptual functions … develop within the same hemisphere, the latter were apparently handicapped in favor of verbal development.” Specifically, there are patients that are born without a corpus callosum, and many times these patients are found to have language abilities in both hemispheres. This added language development seems to be detrimental to non-linguistic functions.


Sperry also discusses left-handers in his article. Left-handers are more likely to show bilateral language development than right-handers. Some studies have found that left-handers are inferior to right-handers in basic perceptual tests for field dependency and tactual localization. One study found that left-handers showed three times greater discrepancy between the verbal and nonverbal performance on the WAIS (an intelligence test) (Levy (1969) as cited in Sperry (1973)). Another study found that patients that had developed right hemisphere speech as a result of early birth injury also had a similar discrepancy (Landsell (1969) as cited in Sperry (1973)). A third study found the left-handers scored very significantly below right-handers on a spatial task. The authors claimed that the scores for the left-handers were so far below those of the right-handers, that their data distributions hardly overlapped at all (Nebes (1971) as cited in Sperry (1973)).


On a side note, Sperry discusses some evidence that language might not always develop as well in people that have bilateral speech development either. A study of four patients that had been stammerers since early childhood found that they all had developed bilateral speech.


Yet again, I find myself needing to bring this back to the discussion of learning styles and specifically to VARK. Sperry and other split brain researchers discuss differences in abilities for left and right hemispheres on various types of tasks. Some of the activities where hemispheric differences in performance were found include language and spatial components. The basis of the VARK theory is that there are individual differences across the visual, auditory, reading/writing, and kinesthetic preferred modes of learning. The obvious parallel is that the right hemisphere may process kinesthetic aspects of things better and the left hemisphere may process reading/writing aspects better. That’s nice and all, but I have to ask… so what?


Here’s the problem with this- simply stating that the two hemispheres do different things and thus we might be unintentionally biasing instruction (or society) against one hemisphere doesn’t mean much. First, the data regarding hemispheric specialization is not perfectly clean. Some studies have shown that a handful of people have bilateral language processing. That is, they can speak with either hemisphere. Other studies have found that speech production may in fact be predominantly a left hemisphere function, but that speech perception (listening and comprehending) is done by both hemispheres. One study used the WADA procedure to put the left hemisphere of the brain “to sleep.” Once the left hemisphere is essentially out of the picture, subjects can be tested and their responses are thought to be the result of the right hemisphere. Subjects were found to be able to understand language, but not produce it (Hickok et al, 2008).


A direct application of the VARK ideas to Sperry’s data would indicate that more right hemisphere applicable tasks need to be introduced into school curricula. However, what about those students that have bilateral language processing? Remember that Sperry discusses evidence that this group is likely to score lower on spatial tasks. So, by introducing more spatial activities into instruction, aren’t we biasing the class against this particular group of students?


VARK theorists may say “What about those students that have higher spatial than verbal abilities?” According to Sperry, when both verbal and non-verbal are forced to develop, the verbal wins out. This is not to say that individuals cannot be better spatially than linguistically. However, those that have developed spatial abilities in one hemisphere probably have developed linguistic abilities in the other. Thus, that group of students should still be able to process things linguistically.


Here’s the other big problem- most of us don’t have split brain. Anything one hemisphere gets is shared with the other hemisphere. So, if instruction is biased to one half of the brain, that should be ok because both hemispheres are getting the information and thus both hemispheres are available to retrieve the information. Most tests in school are conducted in written form. So, the left hemisphere is necessary and dominant for completing the exams. But, who cares? The left hemisphere has access to what the right hemisphere knows, unless we are talking about a split brain patient.


Fleming, N.D. & Mills, C. (1992). Not Another Inventory, Rather a Catalyst for Reflection. To Improve the Academy, 11, 137-155.



 Hickok, G., Okada, K., Barr, W., Pa, J., Rogalsky, C., Donnelly, K., Barde, L. & Grant, A. (2008). Bilateral capacity for speech sound processing in auditory comprehension: Evidence from Wada procedures. Brain and Language, 107, 179-184.


Sperry, R. W. (1961). Cerebral Organization and Behavior. Science, 133(3466), 1749-1757.


Sperry, R. (1973). Lateral specialization of cerebral function in the surgically separated hemisphere. In F. J. McGulgan, & R. A. Schoonover, (Eds.), The psychophysiology of thinking (pp. 209-229). New York. Academic Press.