Short-term memory (अल्पावधि स्मृति) is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recited. The duration of short-term memory (absent rehearsal or active maintenance) is estimated to be on the order of seconds. The commonly cited capacity of 7 items, found in Miller’s Law, has been superseded by 4±1 items. In contrast, long-term memory holds information indefinitely. Short-term memory is not the same as working memory, which refers to structures and processes that temporarily store and manipulate information.
Definition of Short-term memory
Short-term memory refers to the memory systems in the brain involved in remembering pieces of information for a short period, often up to 30 seconds. Short-term memory creates a kind of “visuospatial” sketch of information the brain has recently absorbed and will process into memories later on. By some estimates, short-term memory can hold around seven items of information at one time.
Short-term memory Stores
The idea of separate memories for short-term and long-term storage originated in the 19th century. The model states that memory is first stored in sensory memory, which has a large capacity but can only maintain information for milliseconds.
A representation of that rapidly decaying memory is moved to short-term memory. Short-term memory does not have a large capacity like sensory memory but holds information for seconds or minutes. The final storage is long-term memory, which has a very large capacity and is capable of holding information possibly for a lifetime.
One form of evidence cited in favor of the existence of a short-term store comes from anterograde amnesia, the inability to learn new facts and episodes. Patients with this form of amnesia have an intact ability to retain small amounts of information over short time scales (up to 30 seconds) but have little ability to form longer-term memories (illustrated by patient HM). This is interpreted as showing that the short-term store is spared from damage and diseases.
Other evidence comes from experimental studies showing that some manipulations impair memory for the 3 to 5 most recently learned words of a list. Recall for words from earlier in the list are unaffected. Other manipulations (e.g. the semantic similarity of the words) affect only memory for earlier list words but do not affect memory for the most recent few words.
These results show that different factors affect short-term recall (disruption of rehearsal) and long-term recall (semantic similarity). Together, these findings show that long-term memory and short-term memory can vary independently of each other.
Short-term memory Models
Not all researchers agree that short- and long-term memory are separate systems. The alternative Unitary Model proposes that short-term memory consists of temporary activations of long-term representations. It has been difficult to identify a sharp boundary between short-term and long-term memory.
For instance, Tarnow reported that the recall probability vs. latency curve is a straight line from 6 to 600 seconds, with the probability of failure to recall only saturating after 600 seconds. If two different stores were operating in this time domain, it is reasonable to expect a discontinuity in this curve. Other research has shown that the detailed pattern of recall errors looks remarkably similar to recall of a list immediately after learning (it is presumed, from short-term memory) and recall after 24 hours (necessarily from long-term memory).
One proposed explanation for recency in a continual distractor condition, and its disappearance in an end-only distractor task is the influence of contextual and distinctive processes. According to this model, recency is a result of the similarity of the final items’ processing context to the processing context of the other items and the distinctive position of the final items versus intermediate items. In the end distractor task, the processing context of the final items is no longer similar to that of the other list items.
At the same time, retrieval cues for these items are no longer as effective as without the distractor. Therefore, recency recedes or vanishes. However, when distractor tasks are placed before and after each item, recency returns, because all the list items have similar processing context.
Synaptic theory of Short-term memory
Various researchers have proposed that stimuli are coded in short-term memory using transmitter depletion. According to this hypothesis, a stimulus activates a spatial pattern of activity across neurons in a brain region.
As these neurons fire, the available neurotransmitters are depleted. This depletion pattern represents stimulus information and functions as a memory trace. The memory trace decays over time as a consequence of neurotransmitter reuptake mechanisms that restore neurotransmitters to prior levels.
Relationship of Short-term Memory with Working Memory
The relationship between short-term memory and working memory is described by various theories, but the two concepts are generally considered distinct. Neither holds information for long, but short-term memory is simple storage while working memory allows it to be manipulated. Short-term memory is part of working memory but is not the same thing.
Working memory has been termed working attention. Working memory and attention together play a major role in the thought process. Short-term memory in general refers to the short-term storage of information, and it does not encompass memory manipulation or organization. Thus, while short-term memory components appear in working memory models, the concept of short-term memory is distinct from other concepts.
Short-term memory Duration
The limited duration of short-term memory suggests that its contents spontaneously decay over time. The decay assumption is part of many theories of short-term memory. The most notable one is Baddeley’s model of working memory. The decay assumption is usually paired with the idea of rapid covert rehearsal: to retain information for longer, information must be periodically repeated or rehearsed, either by articulating it out loud or by mental simulation. Another type of rehearsal that can improve short-term memory is attention-based rehearsal. Information is mentally searched in a particular sequence. Once recalled, the information re-enters short-term memory and is then retained for a further period.
One alternative asserts that several elements (such as digits, words, pictures, or logos) are held in short-term memory simultaneously, their representations compete with each other for recall, degrading each other. Thereby, new content gradually replaces older content, unless the older content is actively protected.
Short-term memory Capacity
Whatever the cause(s) of short-term forgetting, consensus asserts that it limits the amount of retained new information short term. This limit is referred to as the finite capacity of short-term memory. Short-term memory capacity often called memory span, about a common measurement procedure. In a memory span test, the experimenter presents a list of items (e.g. digits or words) of increasing length. An individual’s span is determined as the longest list length that he or she can recall correctly in the given order on half or more trials.
In an early and influential article, “The Magical Number Seven, Plus or Minus Two”, Miller suggested that human short-term memory has a forward memory span of approximately seven plus or minus two items and that that was well known at the time (apparently originating with Wundt).
Rehearsal is the process of repeating information to be retained, ostensibly keeping it in short-term memory. Each repetition reenters the information into short-term memory, thus keeping that information for another 10 to 20 seconds (the average storage time for short-term memory).
Chunking is a technique that allows memory to remember more things. For example, in recalling a phone number, chunking the digits into three groups (area code, prefix, and extension). This method of remembering phone numbers is far more effective than attempting to remember a string of 10 digits.
Practice and the usage of existing information in long-term memory can lead to additional improvements in chunking. In one testing session, an American cross-country runner was able to recall a string of 79 digits after hearing them only once by chunking them into groups the size of a running time.
Short-term memory Factors
Diseases that cause neurodegeneration, such as Alzheimer’s disease, can damage short-term as well as long-term memory. Damage to certain sections of the brain due to this disease causes a shrinkage in the cerebral cortex, which impairs the ability to think and recall.
Conditions of Short-term Memory
Memory loss is a natural aging process. Research has reported short-term memory decreases with age. The decline appears to be constant and continuous beginning in the twenties.
One study used data from a previous study that compiled normative French data for three short-term memory tasks (verbal, visual, and spatial). They found impairments in participants between the ages of 55 and 85 years of age.
Memory distortion in Alzheimer’s disease is a disorder common in older adults. One study compared patients with mild to moderate Alzheimer’s disease versus age-matched healthy adults. Alzheimer’s patients had more severely reduced short-term memory.
These studies point to a deficit in visual feature binding as an important component of the deficit. Episodic memory and semantic abilities deteriorate early in Alzheimer’s disease. Since the cognitive system includes interconnected and reciprocally influenced neuronal networks, one study hypothesized that stimulation of lexical-semantic abilities may benefit semantically structured episodic memory. They found that Lexical-Semantic stimulation treatment could improve episodic memory.
Aphasias commonly occur after a left-hemisphere stroke or with neurodegenerative conditions such as primary progressive aphasias. Patients with left temporoparietal focal lesions may suffer a deficit of verbal short-term memory, which may also be a feature of logopenic primary progressive aphasia.
Many language-impaired patients complain about short-term memory deficits. Family members confirm that patients have trouble recalling previously known names and events.
One neglected factor that contributes to those deficits is the comprehension of time. Schizophrenics are not able to process how much time has passed. They are unable to process this because they have impaired temporal information processing.
They can’t tell what the actual time is, what day of the week it is, what month it is, or what year it is. For some, they feel as though time is either sped up or slowed down. This causes them to have instability in life. Not being able to tell time or know what year they are in, forces them to not be able to have a stable life. Schizophrenicscannoto detects rhythm irregularities and estimates durations of time. This affects verbal and psychical abilities. They have a harder time making judgments between multiple events because it is all bound together as one for them.
Post-traumatic stress disorder
Posttraumatic stress disorder (PTSD) is associated with altered processing of emotional material with a strong attentional bias toward trauma-related information. It interferes with cognitive processing. Aside from trauma processing specificities, a range of cognitive impairments have been associated with PTSD state, including attention and verbal memory deficits.
One study examined whether people with PTSD had equivalent levels of short-term, non-verbal memory on the Benton Visual Retention Test (BVRT) and whether they had equivalent levels of intelligence on the Raven Standard Progressive Matrices (RSPM).
They found that people with PTSD had worse short-term, non-verbal memory on the BVRT, despite having comparable levels of intelligence on the RSPM, concluding impairments in memory influence intelligence assessments in the subjects.
How to enhance Short-term Memory?
Before worrying that annoyances like these are signs of a memory problem, try out some simple techniques that may naturally enhance your short-term memory. And here’s some more good news—the list of advice and tips provided below is a great place to start!
Try brain training exercises
Do puzzles or play games that target your memory. Some studies show that brain training games can have a significant impact on cognitive functioning, including memory. There are lots of apps out there with an array of brain training exercises. Choose games or activities that teach you something new, are challenging, have skills you can build on, and are rewarding.
- Try DIY options like studying flashcards or memorizing a string of cards in a deck of cards. Alternatively, have someone set a bunch of everyday items on a table. Look at the table for about 10 seconds, then turn around and see how many of the items you can recall.
- Though there isn’t a consensus in the scientific community on if or how much these types of games improve memory, it certainly doesn’t hurt to try them! Brain training exercises have different effects on different people, so test them out and see if you notice an improvement.
Keep your brain active
Regular mental stimulation may benefit your brain health and memory. Just like your muscles weaken from physical inactivity, brain inactivity may lead to mental decline. It stands to reason that a more active brain is likely to be a more healthy brain and that having a healthy brain will benefit your short-term memory.
- The simple act of having a conversation with another person can benefit your brain health and memory. In addition to talking, consider playing chess, doing puzzles together, or engaging in other activities that challenge your brain to work harder.
- Stimulate your mind when you’re alone as well. Instead of passively watching TV, try reading a book or writing a letter to an old friend.
Eat a brain-healthy diet
Healthy food choices are good for your brain and may improve your memory. Eat plenty of fresh fruits and vegetables, add in lean proteins and whole grains, and cut back on saturated fats, sodium, and sugars.
- The MIND diet (which is a hybrid of the DASH diet and Mediterranean diet) appears to slow down cognitive decline. It prioritizes leafy vegetables, berries, nuts, olive oil, occasional fish consumption, and reduced red meat consumption.
- Drink plenty of water as well. Dehydration negatively impacts the brain along with the rest of the body.
Exercise increases blood flow to your brain, which benefits it overall. Regular exercise, even as simple as walking, boosts the flow of blood—and with it, oxygen and nutrients—your brain needs to be healthy and strong. Moderate-intensity aerobic exercise, which gets your heart pumping faster and increases your breathing rate, even seems to increase the size of the part of your brain that’s responsible for memory.
In general, adults should aim for at least 150 minutes of moderate-intensity aerobic exercise per week for overall health benefits.
Get adequate sleep
Good sleep habits increase your focus and may help encode memories. On the other side of the coin, being alert and focused—thanks to getting adequate, high-quality sleep—improves your short-term memory capabilities. In addition, research indicates that high-quality sleep helps to encode existing memories so that they “stick” much better.
Focus on what you want to remember
Focusing intently for 15-30 seconds may help the memory stick. Therefore, focusing closely on a new piece of info for 15-30 seconds can keep it in your short-term memory and may help transfer it to your long-term memory.
To remember the server’s name at a restaurant, then, give them your full focus when they introduce themselves, then work to keep repeating and thinking about their name for around 15-30 seconds.
Engage multiple senses
Using your senses increases focus and builds memory-helping associations. When you meet someone new, listen carefully and look directly at them as they state their name. Repeat their name immediately afterward. Shake their hand and feel their grip. Even take notice of their perfume or cologne!
Repeating a name, or anything else you want to remember, out loud is always a good way to help strengthen a particular short-term memory. Listen to yourself saying the word or phrase, and keep doing so with regularity.
Utilize mnemonic devices
These visual and verbal techniques help with multiple bits of information. Do you still remember learning “Roy G. Biv” in school to keep track of the order of colors in the rainbow? Mnemonic devices can stick in your memory! Try constructing colorful, even silly visualizations or verbalizations to help encode a group of things in your short-term memory.
- For instance, picture a pile of trash falling onto your head when the clock strikes six to remind you to take out the trash each evening.
- Or, if you’re trying to remember the name of your new co-worker Peggy, imagine her dressed as a pirate with a “peg leg.”
- Singing the “ABC Song” to the tune of “Twinkle, Twinkle, Little Star” is a familiar childhood mnemonic that uses an auditory cue. Mnemonic devices can use a wide range of numbers, colors, and other cues.
Try “chunking” items into groups
Break up more complex things into manageable, organized pieces. Chunking is related to mnemonics and is the principle behind using hyphens to break up 10-digit phone numbers in the U.S.—remembering individual groups of 3, 3, and 4 numbers is easier than recalling a single string of 10. It works even better when you can create associations within each “chunk” — for instance, maybe the “3015” section of a phone number contains the jersey numbers of two of your favorite athletes.
Six smaller shopping lists are easier to recall than one larger one.
Lay out structured associations
Memorize the primary pieces of info and how the secondary pieces relate to them. In other words, prioritize remembering the most vital information, but also focus on memorizing the structure that connects this vital info to the less important material you also want to remember.
For instance, say you’re at a family reunion and are struggling to keep track of the names of four distant cousins, each of whom also has a spouse and kids. For each family group, commit the name of your cousin to memory first (the “central bubble”), then build associations (“lines”) with that name to the names of the other family members (the “surrounding bubbles”).
Address existing health issues
Both illnesses and treatments for illness can impact your memory abilities. In the same way that a healthy body fosters a healthy mind and therefore healthy memory abilities, unhealthiness, and illness can hamper your memory skills. Any circulatory problem that affects blood flow to the brain—high blood pressure, for instance—canhurtn short-term memory. But other conditions like diabetes, thyroid problems, cancers, and so on can likewise have an impact.
- Depression can also negatively impact memory abilities, particularly because it can impede your ability to focus.
- Talk to your doctor if you’re concerned that your medication may be a factor in your memory issues.
- While it’s true that short-term memory loss is one of the first signs of Alzheimer’s disease, the significant majority of people with short-term memory problems do not have that condition.
Reduce your memory demands
Tricks like taking notes help cut back on your memory workload. Simple techniques like jotting down notes, keeping a voice recorder handy, or tying strings on your fingers can help you make it through your daily routines. Using them won’t directly improve your short-term memory, but they can reduce the demands on your memory and therefore reduce your chances of forgetting something.
Sometimes the best way to remember something is to let a sticky note or your smartphone calendar do the “remembering” for you!
In conclusion, short-term memory plays a crucial role in our daily lives, allowing us to retain and manipulate information temporarily. It serves as a mental workspace that enables us to process immediate tasks, such as remembering a phone number or following a conversation.
While short-term memory has limited capacity and is susceptible to forgetting, various strategies can enhance its performance, such as chunking information or rehearsal techniques. Understanding the workings of short-term memory can help us improve our cognitive abilities and optimize our learning and problem-solving skills. Overall, short-term memory is a fundamental cognitive process that influences our ability to function effectively in our day-to-day activities.
Frequently asked questions