by Sandi Mann
There is a wealth of evidence for the existence of Atkinson and Shiffrin’s multi-modal storage system. For example, the Primacy-Recency Effect (Rundus and Atkinson 1970) states that, when presented with lists to remember, we recall first and last items best because the first items have time to be rehearsed into LTM and the last items can be recalled from STM. Studies of amnesiacs whose condition has been caused by Korsakoff’s syndrome (brought on by chronic alcoholism) also provide evidence that suggests the existence of separate and distinct storage systems because they display good STM functioning but impaired LTM.
BADDELEY AND HITCH’S (1974) WORKING MEMORY MODEL
An alternative storage model is suggested by Baddeley and Hitch (1974) and this puts far more emphasis on STM or working memory. In this model, rather than the STM being a single inflexible store, Baddeley and Hitch suggest that the STM is made up of several subsystems, each having a specialized function and each being involved in complex cognitions/thought processes, including analysis and judgements about information input. Evidence for this approach is that people are able to carry out more than one task at once where both tasks involve STM functions.
Although Baddeley and Hitch suggested the existence of several subsystems in STM, they emphasized two in particular, which are governed by a central controlling mechanism that they termed the Central Executive. The Central Executive essentially acts as an attention sensory store. It channels information to two (later three) component processes: the phonological/articulatory loop and the visuo-spatial sketchpad; in 2000 the model was expanded with the introduction of the multimodal episodic buffer.
The visuo-spatial sketchpad deals with visual and spatial information – what information looks like and how it is laid out. It is engaged when performing spatial tasks (such as judging distances) or visual ones (such as counting the windows on a house or imagining images).
The phonological/articulatory loop is the part of working memory that deals with both auditory and written information. It is made up of the phonological store that organizes spoken material by silently rehearsing sounds or words in a continuous loop in what is known as the articulatory process (for example the repetition of a telephone number over and over again). The phonological loop holds spoken information for about 1.5 to 2 seconds. Written words must be converted to spoken words to enter the phonological loop.
The multimodal episodic buffer is dedicated to linking information across domains to form integrated units of visual, spatial and verbal information and chronological ordering (e.g. the memory of a story or a movie scene). The episodic buffer is also assumed to have links to long-term memory.
CRAIK AND LOCKHART’S (1972) LEVELS OF PROCESSING MODEL
This model of memory storage gives LTM a greater role, in particular with regard to the semantic processing that takes place there. Rather than just suggesting that information is transferred to the LTM from the STM through the process of repetition (as in Atkinson and Shiffrin’s multi-modal model), this model suggests that the depth or level at which we process information determines its place in the LTM and also how well we recall that information. In other words, the more we think about it, the more we will remember it (even if we don’t rehearse it). Craik and Lockhart didn’t object to there being different subsytems in LTM, just that the level of processing (shallow, deep or deepest) is key to memory storage.
As an example, consider these three questions:
1 Does the word CAT appear in capital letters or lower case?
2 Does the word CAT rhyme with HAT?
3 Is a CAT a bovine creature or feline?
According to Craik and Lockhart, the first question involves shallow processing as it considers only the appearance of the word. The second question involves deeper processing, looking at how the word sounds. The third question is at the deepest level as this involves semantic (meaning) processing.
Craik and Lockhart suggested that semantic processing can operate at different depths of analysis, some being more complex than others, which they referred to as Elaborate Semantic Processing. They also proposed that the method of learning is important in later recall as well. For example, organizing items into categories helps later recall, making items distinctive in some way helps, and items that have more information associated with them can also be recalled better.
Retrieval
In order for us to remember things, we need to be able to retrieve stored information from our memory. If we can’t remember something, it could be because we are struggling to retrieve it (although it may also be due to the fact that we haven’t encoded it properly or it is not stored effectively).
We retrieve material in different ways dependent on whether the information is stored in short- or long-term storage. It is thought that STM is stored and retrieved sequentially; we need to go through the sequence of memorized information before we get to the bit we need. LTM, however, is stored and retrieved by association. The way we organize information can thus help us with retrieval. For example, we might use the technique of clustering to organize related information into groups.
Types of memory
Two main types of memory are sometimes distinguished:
DECLARATIVE MEMORY
Declarative memory, which requires conscious recall, is when we ‘declare’ information that we have recalled (e.g. in an exam). It is sometimes called explicit memory, since it consists of information that is explicitly stored and retrieved.
Declarative memory can be further subdivided into semantic memory, which concerns facts taken independent of context; and episodic memory, which concerns information specific to a particular context, such as a time and place. Semantic memory allows the encoding of abstract knowledge about the world, such as ‘London is the capital of the UK’. Episodic memory, on the other hand, is used for more personal memories, such as the sensations, emotions and personal associations of a particular place or time. Autobiographical memory – memory for particular events within one’s own life – is generally viewed as either equivalent to, or a subset of, episodic memory.
PROCEDURAL MEMORY
In contrast, procedural memory (or implicit memory) is not based on the conscious recall of information, but on implicit learning. Procedural memory is primarily employed in learning motor skills. It is revealed when one does better in a given task due only to repetition – no new explicit memories have been formed, but one is unconsciously accessing aspects of those previous experiences.
A characteristic of procedural memory is that the things that are remembered are automatically translated into actions, and thus sometimes difficult to describe. Some examples of procedural memory are the ability to ride a bike or drive a car.
Memory failures
Psychologists are interested in why we forget. There are usually three reasons for memory failures. We either did not encode the information effectively, or we struggle to retrieve it, perhaps because the information we are trying to recall is rarely accessed (causing the memory trace to decay). Interference can also affect memory – this is where competing memories interfere with existing ones. There are two types of interference:
• Proactive interference occurs when what we already know interferes with what we are currently learning – where old memories disrupt new memories.
• Retroactive interference occurs when later learning interferes with earlier learning – where new memories disrupt old memories.
The psychologist Hermann Ebbinghaus was one of the first to scientifically study memory failures (otherwise known as forgetting). In 1885 he conducted experiments using three-letter nonsense syllables such as FHG, KYT and so forth. He used these nonsense words because using known words would have made use of existing knowledge and associations in memory and would have allowed a less pure examination of the memory process.
Ebbinghaus tested his own memory for periods of time ranging from 20 minutes to 31 days and plotted his findings in what is now known as the Ebbinghaus Forgetting Curve. The resu
lts showed a relationship between forgetting and time, but this relationship was not as straightforward as might have been expected; initially, information is lost very quickly, with factors such as how the information was learned and how frequently it was rehearsed influencing the speed at which these memories are lost. However, at a certain point, the amount of forgetting levels off, presumably because the data that was last to be lost was laid down in the long-term memory, which is surprisingly stable.
The tip-of-the-tongue phenomenon
The tip-of-the-tongue (TOT) phenomenon is the failure to retrieve a word from memory, combined with the feeling that retrieval is imminent. People can often recall one or more features of the forgotten word, such as the first letter or a word similar sounding or in meaning. People often feel anguish when trying to find the word that is on the ‘tip of their tongue’ and great relief when they locate it.
There are two major competing explanations for the occurrence of TOT phenomenon: the direct-access view and the inferential view. Direct-access view posits that, although the forgotten word does not have enough memory trace to be recalled, it has enough to signal its presence. The inferential view claims that TOTs aren’t completely based on inaccessible, yet activated targets; rather, they arise when the rememberer tries to piece together different clues about the word.
An occasional tip-of-the-tongue state is normal for people of all ages. TOT becomes more frequent as people age.
Spotlight: Deaf people and TOT
Deaf people using sign language experience TOT (or, more accurately, tip-of-the-fingers) phenomenon just as much as speakers. Furthermore, just as speakers can often recall the first letter of the word, signers can sometimes think of part of the sign.
Effects on memory: smell, emotions and stress
MEMORY AND SMELL
It is well known that smells and odours can have a powerful effect on memory. It is thought that the olfactory bulb is located very close to the amygdala, the area of the brain that is connected to the experience of emotion as well as emotional memory. In addition, the olfactory nerve is very close to the hippocampus, which is also associated with memory. So closely are the two related that when people suffer from memory loss (due to ageing or damage) they often suffer from loss of sense of smell, too. But smells would not trigger memories if it weren’t also for conditioned responses. When you first smell a new scent, you link it to an event, a person, a thing or even a moment. Your brain forges a link between the smell and a memory. When you encounter the smell again, the link is already there, ready to elicit a memory or a mood. Because we encounter most new odours in our youth, smells often call up childhood memories.
Spotlight: The power of smells
A well-known idea called the ‘Proustian phenomenon’ proposes that distinctive smells have more power than any other sense to help us recall distant memories. The theory is named after the French writer Marcel Proust, who in his novel A la recherche du temps perdu (In Search of Lost Time) describes a character vividly recalling long-forgotten memories from his childhood after smelling a tea-soaked madeleine.
MEMORY AND EMOTION
Emotion can have a powerful impact on memory. Numerous studies have shown that the most vivid autobiographical memories tend to be of emotional events, which are likely to be recalled more often and with more clarity and detail than neutral events. Memories seem to be treated differently depending on whether they are associated with pleasant positive emotions or unpleasant negative ones. Specifically, pleasant emotions appear to fade more slowly from our memory than unpleasant emotions, partly because they tend to be associated with more contextual cues. Interestingly, among those with mild depression, there is little difference in how long negative and positive memories take to fade.
Mood also affects memory, specifically at the time of encoding or retrieving. Mood congruence theory suggests that we remember events that match our current mood, which is why when we feel happy we remember other happy times, but when we are feeling sad we can recall only other sad events in our lives (and thus get more depressed). Related to this is mood dependence theory, which suggests that remembering is easier when your mood at retrieval matches your mood at encoding.
MEMORY AND STRESS
Stress has a significant effect on memory formation and learning. In response to stressful situations, the brain releases hormones and neurotransmitters that affect memory encoding processes in the hippocampus. In 2009 the German cognitive psychologists Lars Schwabe and Oliver T. Wolf showed that learning under stress decreases memory recall; the researchers suggest that stress experienced during learning distracts people by diverting their attention during the memory encoding process.
However, the impact of stress on memory can be reduced; when the material to be recalled is linked to the learning context, memory is enhanced, even when this learning occurs under stress. This was shown by a separate study by Schwabe and Wolf who found that when memory testing is performed in a context similar to the original learning task (i.e. in the same room), memory impairment and the detrimental effects of stress on learning can be reduced. The researchers gave stressed and non-stressed participants items to learn in a room with the smell of vanilla; their later recall was enhanced in a similar room (i.e. with the vanilla scent) but diminished in a non-similar room (i.e. no vanilla scent). This was true for both stressed and non-stressed participants.
This research may have practical implications; students may perform better when tested in their usual classroom rather than an exam room and eyewitnesses may recall details better at the scene of an event than in a courtroom.
False memory
‘It’s easy enough to explain why we remember things: multiple regions of the brain – particularly the hippocampus – are devoted to the job. It’s easy to understand why we forget stuff too: there’s only so much any busy brain can handle. What’s trickier is what happens in between: when we clearly remember things that simply never happened.’
T. Thean, ‘Remember that: no you don’t’, Time, 19 November 2013 (http://science.time.com/2013/11/19/remember-that-no-you-dont-study-shows-false-memories-afflict-us-all/)
False memory is the psychological phenomenon in which a person recalls a memory of an event that did not actually occur. Memory is not like a video-recorder; it is very prone to fallacy. False memory is often considered in legal cases regarding childhood sexual abuse. False memory syndrome recognizes false memory as a prevalent part of one’s life in which it affects the person’s mentality and day-to-day life. False memory syndrome differs from false memory in that the syndrome has a strong influence on the person’s life, identity, beliefs and values (and on their relationships with other people), while false memory can occur without this significant effect. The syndrome occurs because the person believes the influential memory to be true.
Case study: Language and false memory
In 1974 Elizabeth Loftus conducted a study to investigate the effects of language on the development of false memory. The experiment involved two separate studies. In the first test, 45 participants were randomly assigned to watch different videos of a car accident, in which separate videos showed collisions at 20 miles per hour, 30 miles per hour and 40 miles per hour. Afterwards, participants filled out a survey. The survey asked the question, ‘About how fast were the cars going when they smashed into each other?’ The question always asked the same thing, except that the verb used to describe the collision varied. Rather than ‘smashed’, other verbs used included bumped, collided, hit and contacted. Participants estimated collisions of all speeds to average between 35 miles per hour to just below 40 miles per hour. If actual speed were the main factor in estimate, it could be assumed that participants would have lower estimates when they saw the lower-speed collisions. Instead, the word being used to describe the collision seemed to better predict the estimate in speed rather than the speed itself.
The second experiment also showed participants videos of car accidents, but the critical mani
pulation was the wording of the follow-up questionnaire. One hundred and fifty participants were randomly assigned to three groups. Those in the first groups were asked the same question as in the first study using the verbal form ‘smashed’. The second group was asked the same question as in the first study, replacing ‘smashed’ with ‘hit’. The final group was not asked about the speed of the crashed cars. The researchers then asked the participants if they had seen any broken glass, knowing that there was no broken glass in the video. The responses to this question had shown that the difference between whether broken glass was recalled or not heavily depended on the verb used. A larger number of participants in the ‘smashed’ group declared that there was broken glass.
These studies show that the words used to phrase a question can heavily influence the response given. The second study indicates that the phrasing of a question can create memories of events that did not happen (false memories).
Loftus’s studies paved the way for research into other ways in which ‘false memories’ can be induced. Even the smallest adjustment in wording a question, for example, such as using ‘the’ can alter the responses. So, asking someone if they had seen ‘the’ stop sign, rather than ‘a’ stop sign, provides the respondent with a presupposition that there was a stop sign in the scene they are trying to recall. This presupposition increases the number of people responding that they had indeed seen the stop sign. Similarly, using presupposition can create memories of things that were not there: ‘What shade of blue was his jacket?’ assumes that the jacket was blue, for example, and thus encourages the individual to ‘remember’ the jacket being blue. Asking someone ‘How tall was the gunman?’ will lead to greater estimates of height than asking how short he was. This shows how easily memories can be manipulated.