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Memory is a fundamental cognitive process that allows us to encode, store, and retrieve information. Without memory, we could not learn from experience, form relationships, or carry out the most basic tasks. In psychology, memory is studied as a process rather than a single entity — it involves multiple stages, stores, and types.
Memory involves three key processes:
flowchart LR
A["Sensory information<br/>sights, sounds, ideas"] --> B["Encoding<br/>visual / acoustic / semantic"]
B --> C["Storage<br/>held over time"]
C --> D["Retrieval<br/>back into awareness"]
B -.->|Encoding fails| E[Forgetting]
C -.->|Decay or<br/>interference| E
D -.->|No cue available| E
| Process | Description |
|---|---|
| Encoding | Converting information into a form that can be stored in memory. Information can be encoded visually (as images), acoustically (as sounds), or semantically (by meaning). |
| Storage | Holding information in memory over time. Different memory stores hold information for different durations and in different capacities. |
| Retrieval | Accessing and bringing stored information back into conscious awareness when it is needed. |
If any one of these processes fails, forgetting occurs. For example, information may never be properly encoded in the first place, it may decay from storage over time, or we may be unable to retrieve it even though it is still stored.
Research has shown that different memory stores use different types of encoding:
| Type of Encoding | Description | Example |
|---|---|---|
| Acoustic | Encoding information by how it sounds | Repeating a phone number aloud |
| Visual | Encoding information by how it looks | Remembering a face or a diagram |
| Semantic | Encoding information by its meaning | Understanding a concept rather than just memorising words |
Baddeley (1966) investigated the type of encoding used by short-term and long-term memory. He gave participants lists of words that were either acoustically similar (e.g. cat, cap, can) or semantically similar (e.g. big, large, huge). He found that:
Exam Tip: A common exam question asks you to explain the difference between encoding in STM and LTM. Remember: STM = acoustic, LTM = semantic (based on Baddeley's research).
Duration refers to how long information can be held in a memory store.
| Memory Store | Duration |
|---|---|
| Sensory register | Very brief — less than half a second for iconic (visual) memory, up to 3–4 seconds for echoic (auditory) memory |
| Short-term memory | Approximately 18–30 seconds without rehearsal |
| Long-term memory | Potentially unlimited — information can last a lifetime |
Peterson and Peterson (1959) investigated the duration of STM. Participants were given a trigram (a three-letter nonsense syllable, e.g. BVM) and asked to count backwards in threes from a given number to prevent rehearsal. After 3 seconds, 80% of trigrams were recalled correctly. After 18 seconds, only about 3% were recalled. This study demonstrated that STM has a very short duration (around 18–30 seconds) when rehearsal is prevented.
Capacity refers to how much information a memory store can hold.
| Memory Store | Capacity |
|---|---|
| Sensory register | Very large — all sensory experience is briefly held |
| Short-term memory | Limited — approximately 7 ± 2 items (Miller, 1956) |
| Long-term memory | Potentially unlimited |
George Miller (1956) published a famous paper called "The Magical Number Seven, Plus or Minus Two" which argued that the capacity of STM is approximately 7 items (give or take 2). He also identified a technique called chunking — grouping individual items into larger meaningful units to increase the effective capacity of STM. For example, the sequence 1-9-6-8-1-9-7-4 (8 digits) could be chunked into 1968-1974 (2 chunks), making it easier to hold in STM.
Memory is central to almost every area of psychology:
Understanding memory is therefore foundational to the entire GCSE Psychology course.
Aim: To investigate the duration of short-term memory when rehearsal is prevented. Peterson and Peterson wanted to measure how long information can survive in STM without being actively maintained, and to test whether loss from STM is due to decay over time.
Procedure: The study used 24 university students in a lab experiment with a repeated-measures design. On each trial, a participant was presented with a trigram — a three-consonant nonsense syllable such as BVM or TRG (nonsense was used to avoid meaningful associations). Immediately after, the participant was given a three-digit number (e.g. 491) and asked to count backwards in threes aloud as quickly as possible. This interference task was designed to prevent rehearsal of the trigram. After a retention interval of 3, 6, 9, 12, 15 or 18 seconds, the participant was signalled to recall the trigram. Each participant completed multiple trials at each delay.
Findings: Correct recall fell rapidly with increasing delay:
| Retention interval | Approximate correct recall |
|---|---|
| 3 seconds | ~80% |
| 6 seconds | ~55% |
| 9 seconds | ~40% |
| 12 seconds | ~20% |
| 15 seconds | ~10% |
| 18 seconds | ~3% |
Virtually no trigrams were recalled correctly after 18 seconds of rehearsal prevention.
Conclusion: Information in STM has a very short duration — approximately 18–30 seconds — when maintenance rehearsal is prevented. The rapid loss is consistent with trace decay, supporting the multi-store model's claim that STM is a separate, time-limited store. This is a foundational study for the MSM, Miller's capacity estimate, and the distinction between STM and LTM.
Evaluation (GRAVE):
Myth: "Short-term memory holds everything you've thought about in the last few minutes, and long-term memory holds everything from further back."
Reality: STM and LTM are not defined by how long ago you experienced something, but by how information is encoded, stored, and retrieved. STM has limited capacity (7 ± 2), lasts only 18–30 seconds without rehearsal (Peterson and Peterson, 1959), and is mostly acoustic. LTM has potentially unlimited capacity, can last a lifetime, and is mostly semantic. A memory from ten minutes ago that you are actively holding in mind is still in STM; a detail from childhood you can recall at will is in LTM. A second common myth is that "rehearsing" always means saying something aloud — psychologists distinguish maintenance rehearsal (simple repetition) from elaborative rehearsal (linking information to meaning), and only the latter reliably supports LTM storage.
Exam-style question (9 marks): Describe and evaluate research into the duration, capacity and encoding of memory. (AO1 = 4, AO3 = 5.)
Grade 3-4 response:
Memory has three processes: encoding, storage and retrieval. STM has a duration of 18–30 seconds and a capacity of 7 ± 2 (Miller, 1956). LTM is much bigger. Peterson and Peterson showed that people forget trigrams after 18 seconds. A weakness is the study used nonsense syllables.
Marker comment: Covers three key numbers but limited study detail, thin evaluation. Likely 3-4/9.
Grade 5-6 response:
Memory involves three processes: encoding (converting information for storage), storage, and retrieval. Baddeley (1966) showed STM uses acoustic encoding and LTM uses semantic encoding, because participants made more acoustic errors in STM tasks and more semantic errors in LTM tasks. Miller (1956) said STM has a capacity of 7 ± 2 items and introduced chunking. Peterson and Peterson (1959) found STM has a duration of about 18–30 seconds without rehearsal: after 18 seconds only ~3% of trigrams were recalled. A strength is controlled lab settings. A weakness is that word lists and trigrams are artificial.
Marker comment: Three named studies with data; brief but balanced evaluation. Likely 5-6/9.
Grade 7-9 response:
Memory involves three interacting processes: encoding (transforming information into a storable form — visual, acoustic or semantic), storage (retaining information over time), and retrieval (bringing stored information back into awareness). Research has characterised the three main stores. Baddeley (1966) demonstrated that STM is primarily acoustic and LTM primarily semantic by giving participants acoustically or semantically similar word lists and finding that STM errors clustered around sound while LTM errors clustered around meaning. Miller (1956) argued that STM capacity is 7 ± 2 items and introduced chunking as a way to increase effective capacity. Peterson and Peterson (1959) used trigrams with a backwards-counting distractor task and found correct recall fell from about 80% at 3 seconds to about 3% at 18 seconds, establishing an STM duration of roughly 18–30 seconds without rehearsal.
A strength of this programme of research is its methodological rigour and the convergence of evidence from multiple paradigms. A counterpoint, however, is that most studies use artificial materials (trigrams, word lists), reducing ecological validity and arguably understating real-world STM capabilities. A further limitation is that Peterson and Peterson's distractor task may cause not only decay but also displacement/interference, so the finding does not cleanly prove decay. Application is substantial: capacity and duration findings inform education (chunk size in teaching), consumer design (phone numbers chunked in threes and fours), and explain why writing down a password immediately after hearing it is wise.
Marker comment: Detailed AO1 across three areas, three named researchers with data; AO3 uses strength, counterpoint, methodological limitation, and application. Likely 8-9/9.
AQA mark-scheme cue: Using the precise terminology — acoustic/visual/semantic encoding, 7 ± 2, 18–30 seconds, maintenance vs elaborative rehearsal — and pairing each claim with a named study is the reliable route to the top band. Examiners also reward students who explicitly signpost AO3 with linking phrases such as "this supports...", "a counterpoint to this is..." and "one application of this research is...".
Duration, capacity, and encoding are not just abstract numbers — they together explain everyday experiences of memory. A mobile phone number has roughly 11 digits, which exceeds Miller's 7 ± 2 capacity, which is why we naturally chunk it into smaller groups. We use maintenance rehearsal (acoustic encoding) to keep it alive in STM long enough to dial. If distracted for more than 18–30 seconds without rehearsal, it slips away. To transfer it to LTM we need to recode it semantically — perhaps by noticing a pattern or linking it to something meaningful. This everyday example unites Baddeley (1966), Miller (1956), and Peterson and Peterson (1959) in a single illustration and helps examiners see that a candidate understands the system, not isolated facts.
This content is aligned with the AQA GCSE Psychology (8182) specification, Paper 1: Cognition and behaviour — Memory. For the most accurate and up-to-date information, please refer to the official AQA specification document.