Memory in Learning: Key Concepts and Principles to Enhance Medical Education

Introduction

As discussed in a previous article, the concept of learning has been around for millenia.(1) However, it is only relatively recently that learning theories have been applied and tested in the classroom setting, culminating in a more evidence-based understanding and approach to teaching and learning.(2–4) A similar journey was undertaken in the practice of medicine, leading to the notion of evidence-based medicine—a core tenet of modern medical practice. Originally coined “scientific medicine” by Dr. Gordon Guyatt in 1990, the idea was not well received, since “the implication that current clinical decisions were less than scientific, although probably true, was nonetheless unacceptable to [his fellow staff].”(5) Today, a similar transformation is taking place in education. Drawing a parallel with the medical sciences, the “anatomic” and “physiologic” understanding of the learning process have been greatly enhanced by research produced over the last two decades. In order to ensure a proper transition into evidence-based education and scientific learning, it is necessary to gain an understanding of what learning is and of the foundations of the most robustly supported learning strategies. These strategies will be the focus of multiple articles in this series.

What is Learning?

A simple dictionary definition of learning is “the acquisition of knowledge or skills through study, experience, or being taught.”(6) However, looking at learning from different perspectives provides a more nuanced understanding of what learning is.(7) With a broader understanding of learning, more approaches can be explored to improve learning.

Figure 1. Learning Perspectives

Learning can be seen from multiple perspectives, many of which are based on their own underlying learning theories.(8–10) From an experiential perspective, learning is defined by the learner and happens through experiencing the material. For example, the learner can describe learning as the “retention of knowledge often achieved through repetition and recitation” or adopt a broader definition that is more inclusive.(7) From a behavioral perspective, learning is perceived as a change in a person’s behavior in reaction to a certain stimulus. This view on learning includes the more commonly recognized types of learning from the field of psychology: classical conditioning, operant conditioning, and observational learning.(11) From the neurobiological perspective, in simple terms, learning occurs as changes to the nervous system arising from a person’s experience. It is the “structural basis of learning.”(12) These perspectives, although not inclusive of all theories and definitions of learning, reflect the complex and nuanced nature of learning.

At face value, the significance and relevance of these concepts might not be apparent to a learner or an educator, even for those in the field of medical education. However, these concepts are the foundational principles of many of the evidence-based learning strategies that will be addressed in further articles in this series.

Mastery Learning and Bloom’s Taxonomy

In 1956, Benjamin Bloom, an educational psychologist, and his colleagues compiled a framework for the classification of educational objectives.(13) As part of an educational philosophy and an instructional strategy, it is now referred to as “mastery learning.”(14) This framework, consisting of three hierarchical models, became known as “Bloom’s taxonomy,” and its purpose was to classify learning objectives across levels of complexity and specificity in three domains: cognitive, affective, and sensory.(13)

The cognitive domain was the first published, focused on knowledge-based learning rather than behavioral learning, and garnered popularity with teachers worldwide. The original cognitive domain consisted of six categories of cognitive skills, ranging from lower-order skills requiring less cognitive processing to higher-order skills requiring greater processing and deeper learning.(13)

While widely used, Bloom’s initial taxonomy was criticized for lacking a systematic rationale for its construction and a revised version was published in 2001. This newer version shifted the levels from a noun to a verb format: “Synthesis” became “create,” “knowledge” became “remember,” and “comprehension” became “understand.” “Create” was now the pinnacle of the pyramid.(15)

Figure 2. Bloom’s Taxonomy

For decades, Bloom’s taxonomy has been used as a tool of instructional design by teachers and learners alike, to support the process of learning by ordering the different cognitive skills students need to learn within clear given objectives and helping them to identify their level of mastery within the taxonomy.(16) In any learning setting, with the taxonomy as a reference point, educators can set clear goals for their students, organize them according to difficulty, and assess their students based on that complexity.

The framework provided by Bloom’s taxonomy is not alien to the medical field, despite at times being referred to in slightly different terms. Akresh-Gonzales (2018) strengthens the case for this assertion: “Students and residents (as well as physicians in practice, one could argue) cannot diagnose and treat patients without a foundation of recalling correct information and comprehension of that knowledge. Applying that material to patient care is the next step up on the ladder: ‘formulate’ a solution to a problem, ‘map’ out a plan for treatment, ‘prepare’ a patient for the next step in evaluation.”(17)

It is also important to note the relevance of Bloom’s taxonomy to the assessment of learning. The student’s skill at each level of the pyramid can be assessed in different ways.(18) The figure below demonstrates how the taxonomy can be used as a framework for assessment in a medical education setting.

Figure 3. An Example of Assessment in the Medical Education Setting

A key principle to note is that gaining, understanding and retaining information are foundational for the educational process (and in turn for medical practice). It is for this reason that many learning strategies aim at ensuring long-term retention of knowledge. For these strategies to work, however, they must take into consideration the very basic principles of how information retention works, that is, the processes of memory.

Types of Memory

Memory, the function of preserving information, involves the processes of encoding, storing and retrieving information. It can broadly be divided into two types: short-term and long-term memory.(19) Long-term memory can be further classified as declarative and nondeclarative memory.(20) Declarative memory is more recent on the evolutionary timeline than nondeclarative memory.(21) The primary difference between the two types is that declarative memory is accessible to a person’s awareness, whereas nondeclarative memory is not.(22) This difference can be illustrated by looking at the subtypes within the two types of long-term memory and some examples, noting that the specific types are still a subject of debate among psychologists.(20)

Figure 4. Types of Memory

All these different types of memory serve different functions, have a variety of underlying biological processes, and are not all equally important when it comes to learning. Generally, information is received through sensory inputs, triggering a neurologic cascade of events (action potentials, synaptic release of neurotransmitters, post-synaptic activation, etc.). This biological perspective of memory is what is referred to as neural plasticity.(23) Neurons constantly change based on the individual’s experiences, and these structural changes (specifically in the synapses between neurons) are the foundation of our memory. These changes can be as simple as an increase in the amount of a certain neurotransmitter, or more complex and long term, such as in the case of the synthesis of new proteins that alter the properties of neurons or the formation of new synapses. Some of these changes happen owing to repeated activation, which results in the enhanced strength of synaptic signals, and have been postulated to be direct biological foundations of repetition as a learning strategy.(20)

More relevant to the discussion of learning is that both declarative and nondeclarative memory (specifically, procedural memory) are at play when people learn.(24,25) Information such as facts and events (declarative) is consciously processed through the neocortex,(26) whereas procedural memory is processed through the basal ganglia and happens unconsciously.(27) This difference in consciousness of processing means that explicit instruction can facilitate learning for declarative memory, but not for procedural memory. An example of declarative learning in medical education is learning about the cranial nerves—this involves distinct pieces of factual information that can be explained and processed. However, the ability to promptly and accurately diagnose and manage the cause of a cranial nerve lesion develops more subtly over a longer period and involves a more complex process of learning. This is where a student’s procedural memory is more prominently involved, and this kind of knowledge can only be gained with practice and experience and enhanced with strategies such as spaced retrieval and interleaving.(28)

Memory Process

The memory process is classically described as consisting of three steps, namely encoding, storage, and retrieval.(29)

Figure 5. The Memory Process

Encoding happens after the initial exposure to a stimulus (i.e., the material presented in some perceptual form), which is based on sensory input. It is the first step in the memory process and includes subtypes, such as visual and acoustic encoding.(30) Encoding is a selective process: The brain is constantly being fed sensory information, but only a small portion is remembered, because of the limited capacity of working memory.(31) Historically, a typical person’s working memory was estimated to be able to hold four to eight elements at a time, although there is some variability between individuals.(32)

More recently, it was noted that the limits of memory act independently on each of the channels through which information is encoded (verbal and nonverbal). Thus, using more than one channel to transmit information, that is, dual coding, can enhance the encoding process.(31) This can be illustrated with an example of a medical student attending a class on cardiac valvulopathies. If the student watches an animation that shows what happens during aortic regurgitation, he or she would retain a few mental images highlighting the main points of the process. If this was narrated by a teacher, the student would additionally retain a few key words or phrases, such as “valve opens,” “blood flows back,” and “ventricle.” This limited capacity is outlined extensively in Sweller’s cognitive load theory.(33) 

However, while working memory is limited, long-term memory is practically limitless in capacity.(34) The key to maximal retention, therefore, is to enhance the transfer of information from working memory to long-term memory and to enhance the ability of individuals to retrieve information from their long-term memory. This implicates the second step in the memory process: storage. Memory consolidation, a process of structural and chemical changes that take place on a neural level, is the hallmark of this stage.(35)

During learning, declarative information is processed in the neocortex and the hippocampus.(26) This act of processing forms memories that are temporary and prone to loss, and the use of this information is dependent upon the work of the hippocampus. In order for this information to remain in long-term memory and to be more easily retrieved (eventually without the involvement of the hippocampus) in the future, these memories are reorganized into regions in the neocortex. This act of reorganization is known as consolidation, and it can take days or even months.(26) Research shows that consolidation happens best when the hippocampus is not engaged in encoding new information, essentially being free for consolidation.(36)

This freedom for consolidation is a hallmark of what Barbara Oakley (2014) called diffuse thinking mode.(37) Diffuse thinking refers to a passive internal process of thinking in which the brain is not actively engaged in a specific task. It allows for broader conceptual understanding and linking of new information with previous information. In contrast, focused thinking mode is more targeted toward a specific task. Focused thinking is what a person is engaged in when thinking of a solution to a problem or when consciously thinking about new information as he or she acquires it.

Oakley argues that learning requires both modes of thinking.(37) Intervals of diffuse thinking are paramount for the retention of learned information and thus provide a strong argument for the importance of regular breaks and resting in between study sessions. There is also very strong evidence to support the important role of sleep in memory consolidation, based on years of molecular and phenomenological research.(38) This is also one of the foundational principles of spacing as a learning strategy, which will be discussed in future articles.(39)

Figure 6. Focused vs. Diffuse Modes of Thinking

Although depicted as a separate step in the process, the storage stage is not distinct from encoding. Enhancing the process of encoding improves storage, and this can be achieved in a multitude of ways. Elaborative encoding, for example, entails building new information upon previously acquired information, requiring the learner to actively engage in cognitive processing. This is one of the core ideas of active learning, which has been shown to improve retention of information and improve learning outcomes.(40) Semantic encoding, which is the process of giving meaning to a piece of information, has also been shown to be effective. Its applications include chunking and mnemonics, illustrated in figures 7 and 8.(40) 

Chunking is the process of trying to make sense of a string of information by forming it into meaningful chunks, as depicted in the figure below.(41) The 16 letters on the left are difficult to remember and recite without much memorization, but once chunked into meaningful acronyms, the task becomes much easier. People typically memorize telephone numbers the same way, in chunks of two or three digits: “0300/515/22/19” rather than “03005152219.”

Figure 7. An Example of Chunking

Figure 8. A Common Mnemonic Used by Medical Students

The final step in the memory process is retrieval. This involves the access and utilization of information that has been encoded and stored.(42) Forgetting is most commonly attributed to a failure in retrieval, which highlights the significance of this step.(43) Perhaps the most recognizable application of retrieval in the context of education is assessment, which requires students to retrieve information that they have studied and use it to answer questions. Besides this purpose, retrieving information from long-term memory can also be used to enhance memory consolidation and thus durable learning. For example, in the case of elaborative encoding, information from long-term memory is used as a scaffold on which to build new information. This dynamic interplay between long-term and working memory is the foundation of active learning.(44)

Students’ ability to retrieve information can be enhanced by retrieval exercises, owing to what is referred to by psychologists as the testing effect. The testing effect has been studied for decades and has been demonstrated to be effective for durable learning in multiple educational settings.(40,45) Despite its importance, retrieval is underutilized as a study strategy by students(46) and as a teaching strategy by educators. The use of retrieval-based strategies in medical education will be discussed in depth in a future article on retrieval-based strategies.

Conclusion

A wealth of knowledge has been generated in recent decades about how people learn and how memory works. Considering some basic models of these processes and defining key concepts help educators identify areas and opportunities for learning enhancement. The best learning strategies available today are all based on these principles of learning and memory. However, advice and strategies based on conjecture and ineffective traditional approaches are unfortunately still predominant in academic settings. Understanding these basic concepts and making continual reference to them in designing teaching and learning approaches are important in creating an environment of effective pedagogy. This is paramount in ensuring that educators employ an evidence-based approach to medical education, allowing them to apply strategies that have been empirically proven to work best for learners. To optimize learning, educators need to ensure that the strategies utilized in delivering and reinforcing content are consistent with the understanding of how the human brain processes, stores, and retrieves information. The use of mnemonics, retrieval-based strategies, and strategies that assist with encoding facilitates memory processing and retention and should be employed to maximal effect. The proper timing of the learning process is also crucial in order to allow consolidation of newly learned material.

Self-Quiz

(Please select all that apply)

1. Which statements about Bloom’s taxonomy are correct?

a. Remembering is foundational for the educational process.

b. Bloom’s taxonomy can be used for instructional design and assessment.

c. Evaluation is on the top of the pyramid. 

d. Synthesizing new ideas is foundational for the educational process.

2. Which of the following levels of Bloom’s taxonomy are accurately exemplified?

a. Synthesize: Compare and contrast the characteristics of type 1 and type 2 diabetes mellitus.

b. Evaluate: What factors can contribute to a poorer prognosis in a patient with type 2 diabetes mellitus?

c. Remember: Which of the following cells is responsible for the production of insulin?

3. Which of the following statements are true?

a. Students can be easily taught procedural knowledge in a classroom setting.

b. Declarative information can be enhanced by direct instruction, whereas procedural knowledge is best enhanced by retrieval and practice.

c. Some students rely on declarative memory, while others rely predominantly on procedural memory.

4. Which of the following statements are true?

a. Long-term memory has a capacity limit that varies from one learner to another.

b. Diffuse thinking allows for broader conceptual understanding and linking of new information with previous knowledge.

c. he most common reason for forgetting is a failure in retrieval.

d. In the context of medical education, educators need to consider different memory types and tailor their instruction accordingly.

Correct answers: (1) a, b. (2) c. (3) b. (4) b, c, d.