The Information-Processing Model of Memory (College Board AP® Psychology): Study Guide

The information processing model of memory

• Memory describes all the processes involved with processing, storing, and retrieving information from our experiences

• The information-processing model (also called the multi-store model) was proposed by Atkinson and Shiffrin (1968)

  • It describes memory as three interacting stores that information must pass through in order to be remembered:

    • Sensory memory: the entry point for all incoming sensory information

    • Short-term memory (STM): a temporary, limited-capacity store for information currently being used

    • Long-term memory (LTM): a permanent, potentially unlimited store for information that has been rehearsed and encoded

• Information flows through the stores in sequence

  • Information that is not attended to or rehearsed is lost at each stage

• The model distinguishes between two types of processing:

  • Automatic processing: unconscious encoding of information that occurs without deliberate effort

    • E.g. you automatically encode the time of day, your physical location, and the frequency of events without trying to

  • Effortful processing: conscious, deliberate encoding that requires attention and effort

    • E.g. studying for an exam, rehearsing a phone number, or memorizing a list of vocabulary words

The serial position effect

• The serial position effect is the finding that recall is better for items at the beginning and end of a list than for those in the middle:

  • Primacy effect: items at the beginning are well remembered because they have been rehearsed and transferred to LTM

  • Recency effect: items at the end are well remembered because they are still held in STM at the time of recall

  • Items in the middle are poorly remembered because they have left STM but have not been sufficiently rehearsed to reach LTM

• This pattern supports the MSM, because if memory were a single system, there would be no reason for recall to differ across serial positions

Sensory memory

• Sensory memory is the gateway between perception and memory

• It is a brief holding store for all incoming sensory information before it is processed further

  • All sensory information enters here first, regardless of which sense detected it

  • The capacity of sensory memory is very large, as it holds a snapshot of everything the senses are detecting at any given moment

  • However, most information is held for only a fraction of a second before it fades, therefore sensory memory has a very short duration

• Sensory memory contains separate stores for each sense; two are particularly important:

  • Iconic memory: the sensory store for visual information, which lasts for approximately one quarter to one half of a second

    • E.g. when you move a sparkler quickly in the dark, you perceive a continuous trail of light. This is iconic memory briefly retaining the visual image

  • Echoic memory: the sensory store for auditory (sound) information, which lasts for approximately three to four seconds

    • E.g. when someone speaks to you and you ask "what did you say?", you can often replay the last few words before they have fully faded

• Selective attention determines which information passes from sensory memory into STM

• The brain cannot process all incoming sensory information, so only attended information moves forward

  • E.g. in a noisy environment, you selectively attend to the conversation in front of you, while unattended sensory information fades without being encoded

Short-term memory (STM)

• Short-term memory (STM) holds information that is currently being used or consciously thought about

• STM has three key characteristics:

  • Coding: information in STM is primarily encoded acoustically, as sound

    • E.g. when you try to remember a phone number, you typically repeat it to yourself as sounds, even if you read it visually (Baddeley, 1966)

  • Capacity: STM has a very limited capacity. Miller (1956) suggests it can hold approximately 7 items (+/-2), known as Miller's magic number

    • Capacity can be extended through chunking, which involves grouping individual pieces of information into larger, meaningful units

      • E.g. the string 1-9-4-5-1-9-6-9 is eight individual digits, but chunking it as 1945 and 1969 reduces it to two meaningful units that are easier to hold in STM

  • Duration: STM has a limited duration of approximately 18–30 seconds unless information is actively rehearsed

• Rehearsal is the key process for retaining information in STM and transferring it to LTM:

  • Maintenance rehearsal is the simple repetition of information to keep it in STM

    • E.g. repeating a phone number to yourself until you can write it down

  • Elaborative rehearsal involves deeper processing that connects new information to existing knowledge. This is more effective for transferring information to LTM

    • E.g. linking a new vocabulary word to a word you already know in another language

Long-term memory (LTM)

• Long-term memory (LTM) is the permanent store for all lasting memories and knowledge

• LTM has three key characteristics:

  • Coding: information in LTM is primarily encoded semantically, based on meaning

    • E.g. you remember the meaning of the word "photosynthesis" rather than the specific sound or appearance of the word itself

  • Capacity: LTM has a potentially unlimited capacity, as no evidence has been found for a ceiling on how much can be stored

    • E.g. over a lifetime a person accumulates memories of thousands of events, faces, facts, skills, and experiences without the system becoming "full"

  • Duration: LTM can last a lifetime, though memories can fade or become distorted over time

    • E.g. you can still recall your first day of school decades later, though the details may have shifted over time

Types of LTM

• LTM is not a single store

  • Research shows that memories are differentiated by how they are processed, stored, and retrieved

• Two types of LTM include:

  • Explicit memory (declarative)

    • These are conscious memories that can be easily described or explained to others, e.g.

      • Episodic memory

      • Semantic memory

  • Implicit memory (non-declarative)

    • These are unconscious memories that are more difficult to describe or explain, e.g.

      • Procedural memory

• Prospective memory is memory for future actions — remembering to do something at a later time

  • E.g., remembering to take medication after dinner

• The case study of patient HM provides strong evidence for the distinction between STM and LTM:

  • HM had his hippocampus removed to treat severe epilepsy

  • Following surgery he could recall memories from before the operation, showing his LTM was intact

  • HM could not form any new long-term memories, showing that information in STM could not transfer to LTM

  • This suggests STM and LTM are neurologically distinct systems stored in different brain regions

Long-term potentiation (LTP)

• Long-term potentiation (LTP) is the biological process by which synaptic connections between neurons become stronger with frequent activation

  • Each time two neurons fire together repeatedly, the synaptic connection between them is strengthened

• This makes it easier for that signal to fire in the future

  • This is often summarized as "neurons that fire together, wire together"

    • E.g. the more times you practice recalling a piece of information, the stronger the neural connections associated with that memory become

• LTP depends heavily on the neurotransmitter dopamine, which is involved in pleasurable and rewarding actions

  • This helps explain why emotionally significant or rewarding experiences tend to be better remembered

• LTP provides a neurological explanation for why elaborative rehearsal and repeated retrieval practice are more effective memory strategies than simple repetition