Long-term memory (LTM)

Long-term memory stores information for long periods of time (beyond a few minutes) and has an essentially unlimited capacity. One way to understand how LTM is organized is through semantic (associative) networks. In this model, concepts (categories of language, ideas, or experiences) are linked to related concepts.

When one concept in the network is activated, nearby concepts also receive a smaller increase in activation. This is called spreading activation. Because related ideas are already partially activated (or primed), they’re easier to retrieve. Activation can spread in more than one direction, so you can often reach the same memory through different “routes.” In general, the more connections a concept has, the more likely you are to retrieve it.

Types of long-term memory

1. Explicit (declarative) memory:
   • Conscious effort: Requires active recall or recognition.
   • Example: Studying for an exam.
2. Implicit memory:
   • Unconscious influence: Involves processes you can’t easily describe in words but that still shape your behavior.
   • Procedural memory: Skills like riding a bike or driving a car.
   • Priming: Exposure to a stimulus influences a later response, such as a red octagon priming the concept of “stop.”
3. Episodic memory:
   • Events or experiences: Recollections of significant or meaningful occurrences, such as the details of a natural disaster.
4. Semantic memory:
   • Factual knowledge: Knowing the names of capital cities or historical facts.
5. Autobiographical memory:
   • Personal life history: Includes details about relationships, personal milestones, and emotions.
6. Retrospective memory:
   • Recalling past information: Integrates episodic, semantic, declarative, and autobiographical memories.
7. Prospective memory:
   • Future-oriented tasks: Remembering to perform actions later, such as picking up the dry cleaning.

Retrieval

• Retrieval is the process of bringing stored information back into conscious awareness. It takes several forms:

Recall

• Accessing information without external cues (e.g., essay questions).
  • Serial recall: Remembering in the sequence events happened.
  • Free recall: Spontaneously recalling items with no prompts.
  • Cued recall: Triggered by prompts or hints.
  • Recognition: Identifying previously learned information after seeing it again, as with multiple-choice tests.
  • Relearning: Refreshing or restoring previously acquired knowledge that has faded over time.

Retrieval cues

• Retrieval cues are signals that help you access a memory. They can be external (e.g., a scent) or internal (e.g., an emotion). Intentional cues, such as notes or margin keywords, can also support memory by helping you connect new information to specific prompts. When retrieval cues are missing, too weak, or don’t match the way the memory was stored, retrieval failure may occur, leading to forgetting.

Forgetting and aging

• Short-term decline: Around age sixty, neuron loss can reduce short-term memory capacity.
• Recall vs. recognition: Older adults may find free recall more difficult, though recognition often remains relatively intact.
• Meaningful information: People more easily retain personally significant data, while less important details are more easily lost.