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Active-Mind Psychology

by Chris Clayton
(Preston, Lancashire)

What happens to a thought when it is forgotten about?

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Cognitive psychology, neuroscience, and memory studies
by: Anonymous

The process of forgetting a thought is a complex phenomenon that involves multiple mechanisms within the brain. Understanding what happens to a thought when it is forgotten involves delving into various aspects of cognitive psychology, neuroscience, and memory studies.

Memory Systems and Forgetting

The human brain processes and stores information through different types of memory systems: sensory memory, short-term memory (STM), and long-term memory (LTM). Each of these memory systems plays a role in how thoughts are retained or forgotten.

1. Sensory Memory: Sensory memory holds information from the senses for a very brief period (milliseconds to a few seconds). If attention is not paid to this information, it quickly fades away.

2. Short-Term Memory (STM): Short-term memory, also known as working memory, can hold information for about 15-30 seconds. If the information is not rehearsed or encoded into long-term memory, it is likely to be forgotten.

3. Long-Term Memory (LTM): Long-term memory stores information for extended periods, from hours to a lifetime. However, even in long-term memory, thoughts can be forgotten due to various mechanisms.

Mechanisms of Forgetting

1. Decay Theory: According to decay theory, memories fade over time if they are not accessed or rehearsed. This theory suggests that the physical trace of a thought in the brain's neural network weakens over time, leading to forgetting.

2. Interference Theory: Interference occurs when other information competes with the thought to be remembered. There are two types of interference:

Proactive Interference: Old memories interfere with the retrieval of new information.

Retroactive Interference: New information interferes with the retrieval of old memories.

3. Retrieval Failure: Sometimes, a thought is not lost but is difficult to retrieve. This can happen due to a lack of retrieval cues or because the context in which the thought was encoded is different from the context during recall.

4. Motivated Forgetting: This involves actively trying to forget a thought, often due to its distressing nature. This can happen through repression (unconscious) or suppression (conscious).

Neuroscience of Forgetting

Forgetting involves changes in the brain's neural circuitry. The hippocampus, prefrontal cortex, and amygdala play significant roles in the encoding, storage, and retrieval of memories.

1. Hippocampus: Essential for forming new memories and linking them to existing ones. Damage to the hippocampus can lead to an inability to form new memories (anterograde amnesia) or retrieve old ones (retrograde amnesia).

2. Prefrontal Cortex: Involved in working memory and the organization and retrieval of memories. It helps in filtering out irrelevant information and focusing on what needs to be remembered.

3. Amygdala: Plays a role in emotional memories. Strong emotional experiences can make thoughts more memorable, but excessive stress can also impair memory formation and retrieval.

Research Findings

Research has shown that forgotten thoughts are not entirely erased but may become inaccessible. Studies using neuroimaging techniques have demonstrated that the neural representations of forgotten information can sometimes be reactivated through specific cues or contexts (Johnson, S. K., & Raye, C. L., 2000).

Another study by Anderson and Green (2001) demonstrated the "Think/No-Think" paradigm, where participants were trained to suppress certain memories. The results showed that actively trying to forget a thought can reduce its accessibility over time.

Practical Implications

Understanding the mechanisms of forgetting can have practical implications for improving memory retention. Techniques such as spaced repetition, using mnemonic devices, and creating strong associations can enhance memory retention and reduce forgetting.


Forgetting is a natural and complex process influenced by various factors, including time, interference, retrieval failure, and intentional forgetting. While forgotten thoughts may become less accessible, they are not necessarily erased from the brain. Continued research in cognitive psychology and neuroscience helps unravel the intricacies of memory and forgetting, offering insights into how we can improve our memory retention and recall.


Anderson, M. C., & Green, C. (2001). Suppressing unwanted memories by executive control. Nature, 410(6826), 366-369.

Johnson, S. K., & Raye, C. L. (2000). False memories and confabulation. Trends in Cognitive Sciences, 4(10), 389-396.

Squire, L. R., & Kandel, E. R. (2009). Memory: From Mind to Molecules. W.H. Freeman and Company.

By understanding the processes behind forgetting, individuals can develop strategies to enhance memory retention and better manage their cognitive resources.

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