Human Memory - Solutions

 CBSE Class 11 Pyschology

NCERT Solutions
Human Memory

1. What is the meaning of the terms 'encoding', 'storage' and 'retrieval'?

Ans. Memory is conceptualized as a process consisting of three independent, though interrelated stages. These are encoding, storage, and retrieval. Any information received by us necessarily goes through these stages.


This is the first stage which refers to a process by which information is recorded and registered for the first time so that it becomes usable by our memory system. Whenever an external stimulus impinges on our sensory organs, it generates neural impulses. These are received in different areas of our brain for further processing. In encoding, incoming information is received and some meaning is derived. It is then represented in a way so that it can be processed further.


It is the second stage of memory. Information which was encoded must also be stored so that it can be put to use later. Storage, therefore, refers to the process through which information is retained and held over a period of time.


It is the third stage of memory. Information can be used only when one is able to recover it from her/his memory. Retrieval refers to bringing the stored information to her/his awareness so that it can be used for performing various cognitive tasks such as problem solving or decision-making. It may be interesting to note that memory failure can occur at any of these stages. You may fail to recall an information because you did not encode it properly, or the storage was weak so you could not access or retrieve it when required.

2. How is information processed through sensory, short-term and long-term memory systems?

Ans. Atkinson and Shiffrin in 1968 developed the first model of memory known as Stage Model that was developed from the analogy that human memory processed information in the same way as a computer does.

According to the Stage Model, there are three memory systems : the Sensory Memory, the Short-term Memory and the Long-term Memory. Each of these systems has different features and performs different functions with respect to the sensory inputs.

Sensory Memory

The incoming information first enters the sensory memory. Sensory memory has a large capacity. However, it is of very short duration, i.e. less than a second. It is a memory system that registers information from each of the senses with reasonable accuracy. Often this system is referred to as sensory memories or sensory registers because information from all the senses are registered here as exact replica of the stimulus. If you have experienced visual after-images (the trail of light that stays after the bulb is switched off) or when you hear reverberations of a sound when the sound has ceased, then you are familiar with iconic (visual) or echoic (auditory) sensory registers.

Short-term Memory

You will perhaps agree that we do not attend to all the information that impinge on our senses. Information that is attended to enters the second memory store called the short-term memory (abbreviated as STM), which holds small amount of information for a brief period of time (usually for 30 seconds or less). Atkinson and Shiffrin propose that information in STM is primarily encoded acoustically, i.e. in terms of sound and unless rehearsed continuously, it may get lost from the STM in less than 30 seconds. Note that the STM is fragile but not as fragile as sensory registers where information decays automatically in less than a second.

Long-term Memory

Materials that survive the capacity and duration limitations of the STM finally enter the long-term memory (abbreviated as LTM) which has a vast capacity. It is a permanent storehouse of all information that may be as recent as what you ate for breakfast yesterday to as distant as how you celebrated your sixth birthday. It has been shown that once any information enters the long-term memory store it is never forgotten because it gets encoded semantically, i.e. in terms of the meaning that any information carries. What you experience as forgetting is in fact retrieval failure; for various reasons you cannot retrieve the stored information. 

Each of these memory system is seen as differing in the way they process information, how much information they can hold and for how long they can hold that information.

The model can, be expressed in the following diagram:

3. How are maintenance rehearsals different from elaborative rehearsals?

Ans. Maintenance rehearsal is an important control process of Short-term memory (STM). It retain the information for as much time as required. These kinds of rehearsals simply maintain information through repetition and when such repetitions discontinue the information is lost.

From the STM information enters the long- term memory through elaborative rehearsals. As against maintenance rehearsals, which are carried through silent or vocal repetition, this rehearsal attempts to connect the ‘to be retained information’ to the already existing information in long-term memory. For example, the task of remembering the meaning of the word ‘humanity’ will be easier if the meanings of concepts such as ‘compassion’, ‘truth’ and ‘benevolence’ are already in place. The number of associations you can create around the new information will determine its permanence. In elaborative rehearsals one attempts to analyse the information in terms of various associations it arouses. It involves organisation of the incoming information in as many ways as possible. You can expand the information in some kind of logical framework, link it to similar memories or else can create a mental image..

4. Differentiate between declarative and procedural memories.

Ans. Long-term memory (LTM) contains a wide variety of information consisting of various types. One major classification within the LTM is that of Declarative and Procedural (sometimes called nondeclarative) memories. The following are the differences between declarative and procedural memory.

Declarative Memory

All information pertaining to facts, names, dates, such as a rickshaw has three wheels or that India became independent on August 15 1947 or a frog is an amphibian or you and your friend share the same name, are part of declarative memory. Facts retained in the declarative memory are amenable to verbal descriptions.

Procedural memory

Procedural memory, on the other hand, refers to memories relating to procedures for accomplishing various tasks and skills such as how to ride a bicycle, how to make tea or play basketball. Contents of procedural memory cannot be described easily. For example, when asked you can describe how the game of cricket is played but if someone asks you how do you ride a bicycle, you may find it difficult to narrate. 

5. Discuss the hierarchical organisation in long-term memory?


  • Allan Collins and Ross Quillian suggested that knowledge in long-term memory is organized in terms of concepts, categories and images and are organised hierarchically and assumes a network structure. Elements of this structure are called nodes.
  • Nodes are concepts while connections between nodes are labelled relationships, which indicate category membership or concept attributes.
  • According to this view, we can store all knowledge at a certain level that 'applies to all the members of a category without having to repeat that information at the lower levels in the hierarchy'.
  • This ensures a high degree of cognitive economy, which means maximum and efficient use of the capacity of long-term memory with minimum effort.
  • Images: An image is a concrete form of representation which directly conveys the perceptual attributes of an object.
  • All concrete objects generate images and the knowledge related to them is encoded both verbally as well as visually. This is known as dual coding hypothesis, originally proposed by Paivio. Such information can be recalled with greater ease.
  • According to this hypothesis, concrete nouns and information related to concrete objects are images.
  • Information related to abstract concepts assume a verbal and a descriptive code. For example, if you are asked to describe a bird, the first thing that happens is that an image of a bird is generated and based on this image, you describe a bird. But, on the other hand, the meanings of concepts like 'truth' or 'honesty' will not have such accompanying images.

6. Why does forgetting take place?

Ans. Each one of us has experienced forgetting and its consequences almost routinely.  Many theories have been forwarded to explain forgetting The first systematic attempt to understand the nature of forgetting was made by Hermann Ebbinghaus, who memorised lists of nonsense syllables (CVC trigrams such as NOK or SEP etc.) and then measured the number of trials he took to relearn the same list at varying time intervals. He observed that the course of forgetting follows a certain pattern Although Ebbinghaus’s experiments constituted initial explorations and were not very sophisticated yet they have influenced memory research in many important ways. It is now upheld, almost unanimously, that there is always a sharp drop in memory and thereafter the decline is very gradual. 

The main theories, which have been advanced to explain forgetting are:

Forgetting due to Trace Decay

Trace decay (also called disuse theory) is the earliest theory of forgetting. The assumption here is that memory leads to modification in the central nervous system, which is akin to physical changes in the brain called memory traces. When these memory traces are not used for a long time, they simply fade away and become unavailable. This theory has been proved inadequate on several grounds. If forgetting takes place because memory traces decay due to disuse, then people who go to sleep after memorising should forget more compared to those who remain awake, simply because there is no way in which memory traces can be put to use during sleep. Results, however, show just the opposite. Those who remain awake after memorising (waking condition) show greater forgetting than those who sleep (sleeping condition).

Because trace decay theory did not explain forgetting adequately, it was soon replaced by another theory of forgetting which suggested that new information that enters the long-term memory interferes with the recall of earlier memories and therefore, interference is the main cause of forgetting.

Forgetting due to Interference

A theory of forgetting that has perhaps been the most influential one is the interference theory which suggests that forgetting is due to interference between various information that the memory store contains. This theory assumes that learning and memorising involve forming of associations between items and once acquired, these associations remain intact in the memory. People keep acquiring numerous such associations and each of these rests independently without any mutual conflict. However, interference comes about at a time of retrieval when these various sets of associations compete with each other for retrieval. This interference process will become clearer with a simple exercise. Request your friend to learn two separate lists of nonsense syllables (list A and list B) one after the other and after a while ask her/him to recall the nonsense syllables of list A. If while trying to recall the items of list A, s/he recalls some of the items of list B, it is because of the association formed while learning list B are interfering with the earlier association which were formed while learning list A.

There are atleast two kinds of interferences that may result in forgetting. Interference can be proactive (forward moving) which means what you have learnt earlier interferes with the recall of your subsequent learning or retroactive (backward moving) which refers to difficulty in recalling what you have learnt earlier because of learning a new material. In other words, in proactive interference, past learning interferes with the recall of later learning while in retroactive interference the later learning interferes with the recall of past learning. For example, if you know English and you find it difficult to learn French, it is because of proactive interference and if, on the other hand, you cannot recall English equivalents of French words that you are currently memorising, then it is an example of retroactive interference.

Forgetting due to Retrieval Failure

Forgetting can occur not only because the memory traces have decayed over time (as suggested by the disuse theory) or because independent sets of stored associations compete at the time of recall (as suggested by the interference theory) but also because at the time of recall, either the retrieval cues are absent or they are inappropriate. Retrieval cues are aids which help us in recovering information stored in the memory. This view was advanced by Tulving and his associates who carried out several experiments to show that contents of memory may become inaccessible either due to absence or inappropriateness of retrieval cues that are available/employed at the time of recall.

7. How is retrieval related forgetting different from forgetting due to interference?

Ans. According to Tulving retrieval cues are adds which help us in recovering information stored in the memory.

  • Tulving said that contents of memory may become inaccessible either due to absence or in appropriateness of retrieval cues that are available at the time of recall.
  • According to interference theory of forgetting we forget due to interference between various information the memory store contains.
  • According to this theory learning and memorizing involve forming of associations between items and these associations remain in the memory.

8. What evidence do we have to say that 'memory is a constructive process'?

Ans. "Bartlett" saw memory as a constructive and not a reproductive process.
(i) He used the method of "serial reproduction" in which the participants of his experiments recalled the memory materials reportedly at varying time intervals.

  • While engaging in this method of learning material, his participants committed a wide variety of errors which Bartlett considered useful in understanding the process of memory construction.

(ii) Using meaningful materials such as texts, folk tales, fables etc.

  • He attempted to understand the manner in which content of any specific memory gets affects by a person's knowledge, goals, motivation, preferences and various other psychological process.

(iii) Schemas play an important role in the process of memorization. Schemas refer to an organization of past experiences and knowledge which influence the ·way in which incoming information is interpreted, stored and later retrieved.

  • Memory, therefore becomes encoded and is stored in terms of a person's understanding and within his/her previous knowledge and expectations.

9. Define Mnemonics? Suggest a plan to improve your own memory.

Ans. All of us desire to possess an excellent memory system that is robust and dependable.  There are a number of strategies for improving memory called mnemonics (pronounced ni-mo-nicks) to help you improve your memory. Some of these mnemonics involve use of images whereas others emphasise self-induced organisation of learned information. 

Mnemonics using Images

Mnemonics using images require that you create vivid and interacting images of and around the material you wish to remember. The two prominent mnemonic devices, which make interesting use of images, are the keyword method and the method of loci.

  • The Keyword Method : Suppose you want to learn words of any foreign language. In keyword method, an English word (the assumption here is that you know English language) that sounds similar to the word of a foreign language is identified. This English word will function as the keyword. For example, if you want to remember the Spanish word for duck which is ‘Pato’, you may choose ‘pot’ as the keyword and then evoke images of keyword and the target word (the Spanish word you want to remember) and imagine them as interacting. You might, in this case, imagine a duck in a pot full of water. This method of learning words of a foreign language is much superior compared to any kind of rote memorisation.
  • The Method of Loci : In order to use the method of loci, items you want to remember are placed as objects arranged in a physical space in the form of visual images. This method is particularly helpful in remembering items in a serial order. It requires that you first visualise objects/places that you know well in a specific sequence, imagine the objects you want to remember and associate them one by one to the physical locations. For example, suppose you want to remember bread, eggs, tomatoes, and soap on your way to the market, you may visualise a loaf of bread and eggs placed in your kitchen, tomatoes kept on a table and soap in the bathroom. When you enter the market all you need to do is to take a mental walk along the route from your kitchen to the bathroom recalling all the items of your shopping list in a sequence. 

Mnemonics using Organisation

Organisation refers to imposing certain order on the material you want to remember. Mnemonics of this kind are helpful because the framework you create while organisation makes the retrieval task fairly easy.

  • Chunking : While describing the features of short-term memory, we noted how chunking can increase the capacity of short-term memory. In chunking, several smaller units are combined to form large chunks. For creating chunks, it is important to discover some organisation principles, which can link smaller units. Therefore, apart from being a control mechanism to increase the capacity of short-term memory, chunking can be used to improve memory as well. 
  • First Letter Technique : In order to employ the first letter technique, you need to pick up the first letter of each word you want to remember and arrange them to form another word or a sentence. For example, colours of a rainbow are remembered in this way (VIBGYOR- that stands for Violet, Indigo, Blue, Green, Yellow, Orange and Red).

Mnemonic strategies for memory enhancement are too simplistic and perhaps underestimate complexities of memory tasks and difficulties people experience while memorising. In place of mnemonics, a more comprehensive approach to memory improvement has been suggested by many psychologists. In such an approach, emphasis is laid on applying knowledge about memory processes to the task of memory improvement. Some of them are:

Engage in Deep Level Processing : I

f you want to memorise any information well, engage in deep level processing. Craik and Lockhart have demonstrated that processing information in terms of meaning that they convey leads to better memory as compared to attending to their surface features. Deep processing would involve asking as many questions related to the information as possible, considering its meaning and examining its relationships to the facts you already know. In this way, the new information will become a part of your existing knowledge framework and the chances that it will be remembered are increased.

Minimise Interference :

Interference, as we have read, is a major cause of forgetting and therefore you should try to avoid it as much as possible. You know that maximum interference is caused when very similar materials are learned in a sequence. Avoid this. Arrange your study in such a way that you do not learn similar subjects one after the other. Instead, pick up some other subject unrelated to the previous one. If that is not possible, distribute your learning/practice. This means giving yourself intermittent rest periods while studying to minimise interference. 

Give Yourself enough Retrieval Cues :

While you learn something, think of retrieval cues inherent in your study material. Identify them and link parts of the study material to these cues. Cues will be easier to remember compared to the entire content and the links you have created between cues and the content will facilitate the retrieval process.