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Implicit and Explicit Memory

By Ayesh Perera, published October 26, 2020


Take-home Messages
  • Implicit memory and explicit memory represent the distinct neural processes and the different states of awareness of our long-term memory.
  • The discovery of implicit memory and explicit memory stemmed from the treatment of a patient suffering from amnesia. Typically, amnesic patients have great difficulty in retaining episodic and semantic information following the onset of amnesia.
  • While implicit memory involves perceptional and emotional unconscious memories, explicit memory involves information and experiences we can consciously recall.
  • Despite much research and many studies, the exact nature of the relationship between implicit memory and explicit memory is still ambiguous.

Our long-term memory can be fundamentally divided into two distinct types, namely implicit memory and explicit memory (Squire, 2004).

It should be noted that the formation of explicit memories requires several rounds of stimulation, significant effort and considerable time. Alternatively, the learning and retention of implicit memories may be triggered by a single stimulus.

Moreover, while implicit memory relies on specified areas of the brain, explicit memory depends upon multicomponent brain links involving the brain’s cortical and temporal regions.

Differences between implicit and explicit memory

Origin and Development

The discovery of implicit memory and the explicit memory stemmed from the treatment of the neuroscience patient, Henry Gustav Molaison (Squire, 2009).

An attempt to cure his epilepsy via a bilateral medial temporal lobotomy destroyed parts of Molaison’s brain. Consequently, he suffered from amnesia. Although following the surgery, Molaison was able to form short-term memories, his long-term memory was impaired.

Molaison was able to quickly learn skills such as hand to eye coordination. However, he could not recall events from his former days prior to the surgery.

Memory for events and knowledge acquired before the onset of amnesia tend to remain intact, but amnesiacs can’t store new episodic or semantic memories. In other words, it appears that their ability to retain declarative information is impaired.

However, their procedural memory appears to be largely unaffected. They can recall skills they have already learned (e.g. riding a bike) and acquire new skills (e.g. learning to drive).

The nature of Molaison’s amnesia provided scientists insight into the workings of different memory systems as well as the brain structures governing their functioning.

In addition to Molaison’s case, the study of patients suffering from various forms of neurodegeneration and trauma too, has developed our understanding of implicit and explicit memory (Squire, 2015).

For instance, examining how the damaged hippocampus of patients with Alzheimer’s disease impacts their ability to create and retain explicit memories has generated important discussion.


What is Implicit Memory?

Implicit memory, also known as unconscious memory or automatic memory, refers to perceptional and emotional unconscious memories which influence our behavior (Dew & Cabeza, 2011).

The impact which implicit memory has on our current behavior occurs without our conscious retrieval of memories.

Hence, implicit memory enables our prior experiences to improve our performance of various tasks without our conscious and explicit awareness of such experiences.

Types of Implicit Memory

  • Procedural Learning: Procedural memory is part of of implicit memory that is responsible for knowing how to perform a of particular types of action, such as reading, tying shoes and riding a bike. Procedural memories are automatically retrieved for the execution of procedures involved in both cognitive and motor skills. This enables task performance without the need for conscious control or attention. The association of procedural learning with muscle memory can make certain actions second nature (Bullemer, Nissen, & Willingham, 1989).
  • Priming: Priming is a non conscious form of human implicit memory concerned with perceptual identification of words and objects. Priming can be associative, negative, positive, affective, conceptual, perceptual, repetitive, or semantic. The subtle effects which this complex psychological phenomenon encompasses can be employed to manipulate individual behavior.
  • Category Learning: Category learning involves the attainment of a concept in order to clarify and categorize various entities via grouping (Ell, Shawn; Zilioli, & Monica, 2012). Category learning allows for comparisons and indicates subjective divisions for better comprehension.
  • Perceptual Learning: Perceptual learning constitutes the foundation for cognitive processes, and cooperates with the neural basis to produce the prime effect. Perceptual learning also improves perception by enabling the distinguishing of similar things from each other.
  • Emotional Learning: Emotional learning which involves autobiographical memories entangled with emotions, refers to the impact of emotions upon an individual.

Examples of Implicit Memory

Some examples of implicit memory include knowing how to play the piano, ride a bike; tie your shoes and other motor skills. These skills involve procedural knowledge which involves “knowing how” to do things.

Other examples of implicit memory may include:

  • Knowing how to make breakfast.
  • Knowing how to play a musical instrument.
  • Navigating a familiar area such as your house or neighborhood.

Skills using implicit memory do not involve conscious thought (i.e. they are unconscious and automatic). For example, we brush our teeth with little or no awareness of the skills involved.

Related Brain Structures

The functioning of implicit memory is thought to involve the cerebellum and the basal ganglia (Dew & Cabeza, 2011). The cerebellum which is essential for procedural memories is located at the base of the brain.

Although it does not initiate actions, the cerebellum receives and coordinates signals from the spinal cord, the brain and sensory systems to carry out motor movements. & Cabeza, 2011). The cerebellum which is essential for procedural memories is located at the base of the brain.

The cerebellum which forms the hindbrain is primarily responsible for skill development as well as a few cognitive tasks such as attention and language (13.2 The Central Nervous System – Anatomy and Physiology, 2013). & Cabeza, 2011). The cerebellum which is essential for procedural memories is located at the base of the brain.

The basal ganglia, on the other hand, which engage in action selection, are essential for the smooth controlling of sequential movements (Ullman, 2004). Responsible for processes such as habit formation and the regulation of emotions, the basal ganglia consist of a pair of structures deep inside the brain. & Cabeza, 2011). The cerebellum which is essential for procedural memories is located at the base of the brain.

The basal ganglia’s constitution explains why implicit memory involves subconsciously driven sensorimotor behavior which we typically remain unaware of.


What is Explicit Memory?

Explicit memory, also known as declarative memory, refers to memories involving personal experiences as well as factual information which we can consciously retrieve and intentionally articulate (Dew & Cabeza, 2011).

Recalling information from explicit memory involves some degree of conscious effort – information is consciously brought to mind and “declared”.

For example, declarative knowledge involves “knowing that” London is the capital of England, zebras are animals, and the date of your mom's birthday etc (Cohen & Squire, 1980) .

Types of Explicit Memory

  • Semantic Memory: Semantic memory is a part of the long-term memory responsible for storing information about the world. This includes knowledge about the meaning of words, as well as general knowledge. For example, London is the capital of England. It involves conscious thought and and is declarative.
  • Episodic Memory: Autobiographical memory involves various episodes from the past gathered from our personal history based on a certain time, space, object, or person. Autobiographical memories often combine episodic and semantic memories.
  • Autobiographical Memory: Episodic memory is type of long-term memory responsible for storing information about events (i.e. episodes) that we have experienced in our lives. Episodic memories involve conscious thought and can be declared explicitly. An example would be a memory of our 1st day at school.
  • Spatial Memory: Spatial memory is crucial for the formation of cognitive maps. It involves the recording of facts concerning an individual’s spatial arrangement. Spatial memory accounts for our ability to readily find our way through familiar towns.

Examples of Explicit Memory

The knowledge that we hold in semantic and episodic memories focuses on “knowing that” something is the case (i.e. declarative).

For example, we might have a semantic memory for knowing that Paris is the capital of France, and we might have an episodic memory for knowing that we caught the bus to college today.

Other examples of explicit memory may include:

  • Recollecting the items on a to-do list.
  • Remembering the dates of various events for a history exam.
  • Remembering the time for a doctor’s appointment.

Related Brain Structures

Explicit memory is governed by communications between the prefrontal cortex, the amygdala and the hippocampus (Dew & Cabeza, 2011).

The prefrontal cortex is thought to be necessary to store and retrieve long-term memories involving information and facts (13.2 The Central Nervous System – Anatomy and Physiology, 2013).

Located deep within the brain’s temporal lobe, the hippocampus is essential for spatial awareness and navigation as well as the consolidation of information from a short-term to a long-term memory (Squire, 2015).

The hippocampus does not involve implicit memory. The amygdala which engages in emotional learning is located near the hippocampus.

While the retention and the recalling of events rely on the function of the hippocampus, the declarative inside the brain’s medial temporal lobe is consolidated into the temporal cortex (Squire, 2009).



The Relationship between the Two Memory Systems

While recent evidence suggests a significant impact of implicit memory’s priming on explicit memory’s fact recalling, the two memory systems are thought to work independently with fundamentally distinct rules of operation (Squire, 2004).

The study of amnesic patients implies a separation of implicit and explicit memory. For instance, on one occasion, some amnesic patients with severely impaired long-term verbal memories demonstrated no difficulty in mastering a certain puzzle even though they could not recall having seen the same puzzle before (Brooks & Baddeley, 1976).

While damage to the hippocampus may explain the loss of explicit memory, the loss of their ability for conscious remembering seems to have still left intact various residual learning abilities. Despite this apparent separation, implicit memory and explicit memory seem to work in parallel to shape our behavior (Squire, 2015).

The relationship between the two memory systems may also be influenced by chronic drug use, aging and stress. In spite of manifold studies and much research however, the exact nature of this relationship is still ambiguous (Dew & Cabeza, 2011).

Consequently, whether the two memory systems are cooperating with, or competing against each other is yet to be discovered.

About the Author

Ayesh Perera recently graduated from Harvard University, where he studied politics, ethics and religion. He is presently conducting research in neuroscience and peak performance as an intern for the Cambridge Center for Behavioral Studies, while also working on a book of his own on constitutional law and legal interpretation.

How to reference this article:

Prera, A (2020, Oct 26). Implicit and explicit memory. Simply Psychology. https://www.simplypsychology.org/implicit-versus-explicit-memory.html

APA Style References

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How to reference this article:

Prera, A (2020, Oct 26). Implicit and explicit memory. Simply Psychology. https://www.simplypsychology.org/implicit-versus-explicit-memory.html

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