The field of cognitive psychology has long been interested in understanding the workings of human memory. One key distinction that has been drawn is between short-term memory (STM) and long-term memory (LTM). Although STM and LTM both play crucial roles in human cognition, they differ in terms of capacity, duration, encoding, and retrieval.
Short-term memory, also known as working memory, is the system that temporarily holds and manipulates information that is currently in use. It allows individuals to maintain and manipulate a limited amount of information for a short period, usually around 15-30 seconds. STM has a limited capacity, typically estimated to hold around 7 ± 2 items, known as the “magic number” proposed by George Miller in 1956. This capacity can vary depending on factors such as the nature of the stimuli and an individual’s level of expertise.
The duration of STM is relatively short compared to LTM. In the absence of rehearsal, information in STM is prone to rapid decay and can be easily lost or overwritten by new incoming information. However, with active rehearsal or attention to the information, it can be held in STM for a longer period. For example, when trying to remember a phone number, individuals engage in rehearsal by repeating the digits in their mind until they can write them down.
Encoding in STM primarily relies on acoustic and phonological processes. Information is typically stored in STM in a phonological loop, which involves the temporary maintenance of auditory or phonological representations. This can be seen in experiments that demonstrate the phonological similarity effect, where participants have difficulty remembering sets of words that sound similar (e.g., cat, bat, mat) compared to sets of words that sound different (e.g., cat, cup, pie).
Retrieval from STM is fast and effortless. As information is readily available and easily accessible, it can be retrieved and used for ongoing mental tasks without much effort. For example, in a conversation, individuals can effortlessly recall and use recently heard information from STM to engage in meaningful dialogue.
On the other hand, long-term memory is the system responsible for storing vast amounts of information over extended periods, ranging from minutes to years. Unlike STM, LTM has an essentially unlimited capacity. It is believed to have a virtually infinite capacity to store and organize information.
The duration of LTM varies depending on the specific type of memory. Declarative memories, which include facts and events, can last from days to a lifetime. However, some memories may become more difficult to retrieve as time passes, potentially due to interference or decay. Procedural memories, which include skills and habits, can last even longer and may become automatic with practice.
Encoding in LTM involves the transformation of information from STM into a format that can be stored and retrieved later. Encoding in LTM is believed to rely on semantic processes, which involve assigning meaning to the information. For example, when learning new vocabulary words, individuals often relate them to familiar concepts or make connections to their own experiences, which facilitates encoding and retrieval.
Retrieval from LTM is slower and requires effort compared to STM. Retrieval cues or prompts are often needed to access memories stored in LTM. These cues can be internal (e.g., contextual cues) or external (e.g., specific questions or prompts). The process of retrieval involves reconstructing the stored information based on the available cues, which can sometimes lead to errors or distortions in memory.
In summary, short-term memory and long-term memory are distinct systems that differ in terms of capacity, duration, encoding, and retrieval. STM has a limited capacity and short duration, relies on acoustic and phonological encoding, and allows for fast and effortless retrieval. In contrast, LTM has an unlimited capacity, longer duration, relies on semantic encoding, and requires effortful retrieval. Understanding the differences between STM and LTM is crucial for understanding human memory processes and their implications for cognitive functioning.