Assignment: Human Memory

Assignment: Human Memory

Assignment: Human Memory

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It is good to have an end to journey towards; but it is the journey that matters, in the end.

Ursula K. Le Gui

http://www.wnyc.org/shows/radiolab/episodes/2007/06/08

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Stage theory of memory
Assumes humans have 3-stage
Memory

Process by which information is:
Recording
Encoding
Stored in the brain
Storage
Later retrieved
Retrieval
Eventually (possibly) forgotten
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Our memory is the process by which information is retained for later use. The basic process by which information is processed follows this format: information is acquired and encoded, which leads to storage in the brain, which leads to the possibility of later retrieval (though as you know at test time, is not a guarantee), and the possibility of eventually forgetting the information.

Today, cognitive psychologists like to compare the human mind to a computer and memory to an information-processing system. I think you can appreciate the analogy. Your PC acquires (or receives) input from a keyboard or a mouse; it converts the symbols into a special numeric code; it saves the information on a hard drive, CD, or disk; it then retrieves the data from the disk to be displayed on a screen or sends it to a printer. If the computer crashes, if there’s not enough space on the disk, if the file was deleted, or if you enter the wrong retrieval command, the information becomes inaccessible, or ‘forgotten’.

Three-System Approach to Memory

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Three-System Approach to Memory

Three types of memory
Sensory memory
Only an instant
Short-term memory (STM)
15-25 seconds
Long-term memory (LTM)
Can hold vast quantities of information and relatively permanent
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Using the computer as a model, memory researchers seek to trace the flow of information as it is mental processed. In this Three-System Approach to Memory, a stimulus that registers on our senses can be remembered only if it 1. Draws attention, which brings it into consciousness; 2. Is encoded, or transferred to storage sites in the brain, and 3. Is retrieved for use at a later time.

Within this information-processing memory approach, three types of memory have been distinguished: sensory, short-term and long-term. Sensory memory stores all stimuli that register on the senses, holding literal copies for a brief moment ranging from a fraction of a second to four seconds usually less. Sensations that do not draw attention tend to vanish, but those we ‘notice’ are transferred to short-term memory , another temporary storage system that can hold seven or so items of information for about 20 seconds, less than 1 minute. Although STM fades quickly, information can be held for a longer period of time through repetition and rehearsa or chunkingl. When people talk about attention span, they are referring to short-term memory.

Finally, long-term memory is a somewhat permanent storage system that can hold vast quantities of information for many years. Science writer Isaac Asimov once estimated that LTM takes in a quadrillion separate bits of information in the course of a lifetime. Mathematician John Griffith estimated that, from birth to death, the average person stores five hundred times more information than the Encyclopedia Britannica. When people talk about memory, long-term memory is typically what they have in mind.

We’ll talk about each of these in a little more detail later on.

Information-Processing Model of Memory

Short-term

memory

Stimulus

Sensory

memory

Long-term

memory

Attention

Encoding

Retrieval

Forgetting

Forgetting

Forgetting

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Many events register in sensory memory. Those that are noticed are briefly stored in short-term memory; those that are encoded are transferred to a more permanent facility. As shown forgetting may be caused by failures of attention, encoding, or retrieval.

Note, however, that this is only a model and does NOT mean that the brain has three separate storage bins. This is only one view of how memory works. There is a radically different view. Most computers process instructions in fixed sequence, one linear step at a time. In contrast, the human brain performs multiple operations simultaneously, ‘in parallel’. Thus, some cognitive psychologists have rejected the information-processing model in favor of parallel-processing models in which knowledge is represented in a web-like network of connections among thousands of interacting ‘processing units’ all active at once.

The two main questions we’ll be asking ourselves throughout this chapter are: How are memories stored? And to what extend are our memories of the past faithful to reality?

Sensory Memory

Two types
Iconic memory
Visual
Lasts less than a sec
Sperling’s tests (1960s)
Echoic memory
Auditory
Fades within 2-3 sec
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Take a flashlight into a dark room, turn it on, shine it on a wall, and wave it quickly in a circular motion. What do you see? If you twirl it fast enough, the light will appear to leave a glowing trail, and you’ll see a continuous circle. The reason: Even though the light illuminates only one point in the circle at a time, your visual system stores a ‘snapshot’ of watch point as you watch the next point. The visual image is called an icon, and the snapshot it stores is called iconic memory.