Declarative/Nondeclarative Memory

Declarative vs. Nondeclarative Memory: The Distinctive Features

It has been argued that the most distinction between different types of long-term memory is between declarative memory and nondeclarative memory.

Declarative memory involves conscious recollection of events and facts — it often refers to memories that can be declared or described but also includes memories that cannot be described verbally. It involves knowing that something is the case.

The two main forms of declarative memory Opens in new window are episodic memory and semantic memory.

• Episodic memory   Opens in new window is concerned with personal experiences or events that occurred in a given place at a specific time.
• Semantic memory   Opens in new window consists of general knowledge about the world, concepts or abstract representations, language and so on.

Nondeclarative memory, in contrast does not involve conscious recollection. Typically, we obtain evidence of nondeclarative memory by observing changes in behavior.

For example, consider someone learning how to ride a bicycle. Their cycling performance improves over time even though they cannot consciously recollect what they have learned about cycling.

Nondeclarative memory consists in various forms. One common form is procedural memory Opens in new window which involves knowing how to perform certain learned actions (e.g., playing a piano, riding a bicycle).

Priming Opens in new window is another form of nondeclarative memory, in which the processing of a stimulus is influenced by the prior presentation of a stimulus related to it.

For example, suppose a visual stimulus (e.g., of a cat) is presented very briefly. It is easier to identify the stimulus as a cat if a similar picture of a cat has been presented previously. The earlier picture acts as a prime, facilitating processing when the second cat in picture is presented.

Another distinctive feature is that declarative memory is fast, flexible and infallible, in that memory traces deteriorate over time and are subject to retrieval failures and high levels of reconstruction. Thus, declarative memory Opens in new window is probably most vulnerable to distortion.

In contrast nondeclarative memory is slow, reliable and inflexible. Recollection in nondeclarative memory Opens in new window is not associated with a specific episode, and learning proceeds gradually as a result of repeated practice.

These observed differences suggest that declarative memory is essentially subject to controlled processing and conscious recollection, whereas nondeclarative memory is subject to automatic processing and nonconscious recollection.

However, this rigid distinction has been challenged by Anderson (1982), who argues that initially we encode and learn declaratively but with practice the actions become compiled into a nondeclarative or procedural form of knowledge Opens in new window.

Thus, nondeclarative memory refers to internal representations of stimulus-response connections, particularly with reference to frequent motor actions performed automatically, such as brushing one’s teeth, writing or riding a bicycle.

In addition to the psychological differences between declarative and nondeclarative memory, there may also be biological differences in terms of how the two types of memory are implemented in the brain.

Positron-emission tomography (PET) Opens in new window brain-scanning experiments demonstrate that during retrieval processes utilizing the declarative memory system, the main areas of brain activity are located in the hippocampus Opens in new window and the right hemisphere. When operationalizing the nondeclarative memory system during recall, brain activities in these areas are considerably reduced(Squire et al 1992).

Evidence from amnesic patients is very relevant to the distinction between declarative and nondeclarative memory. It appears such patients have great difficulties in forming declarative but can readily form nondeclarative memories.

For example, HM Opens in new window had extremely poor declarative memory for personal events occurring after the onset of amnesia and for faces of those who became famous in recent decades. However, he had reasonable learning ability on tasks such as mirror tracing, the pursuit rotor and perceptual identification (all involving nondeclarative memory). Studies have shown that the great majority of amnesic patients have patterns of memory performance similar to those of HM.