Memory Basics: Coding, Capacity and Duration

Your brain doesn't just randomly stuff information anywhere - it has specific ways of coding (storing), measuring capacity (how much), and duration (how long) memories last.

Short-term memory (STM) codes information acoustically (by sound), which Baddeley discovered when people struggled more with similar-sounding words. Meanwhile, long-term memory (LTM) codes semantically (by meaning). Think about it - you remember the gist of conversations, not the exact sounds.

For capacity, Jacobs found we can hold about 4-7 items in STM, whilst Miller's famous research suggested 7±2 items as our limit. However, you can cheat this system through chunking - grouping information together (like remembering phone numbers in segments). LTM has unlimited capacity, so you'll never run out of space for new memories!

Remember: STM = acoustic coding, limited capacity (7±2). LTM = semantic coding, unlimited capacity.

How Long Memories Last

Duration is basically your memory's expiry date, and the news isn't great for short-term storage.

Peterson & Peterson's research showed that STM duration is only 18-30 seconds without rehearsal. Students trying to remember consonant syllables could barely recall 3% after just 18 seconds - your brain literally dumps information that quickly!

Long-term memory tells a completely different story. Bahrick's brilliant study tested people's memory for classmates' faces up to 48 years after graduation. Even decades later, participants were 70% accurate at photo recognition. This proves LTM duration is essentially unlimited - those embarrassing school memories aren't going anywhere!

The key difference? Without active rehearsal or meaningful connection, information vanishes from STM faster than a Snapchat message.

Fun fact: You can recognise faces from school decades later, but forget someone's name 30 seconds after meeting them!

The Multi-Store Model of Memory

Picture your memory as a filing system with three distinct sections, each with its own job and limitations.

The sensory store briefly holds information from your environment (less than half a second). Most of this gets binned immediately unless you pay attention to it. What survives moves to STM - your mental workspace with acoustic coding, 7±2 capacity, and that 18-30 second duration limit.

Through maintenance rehearsal (basically repeating stuff to yourself), information can transfer to LTM. This final store has semantic coding, unlimited capacity, and can last a lifetime. When you need to recall something, it travels back from LTM to STM.

This model treats STM and LTM as separate, unitary stores - like different filing cabinets rather than one complex system. It's supported by research on coding, capacity and duration, but critics argue it oversimplifies how memory actually works.

Think of it like: Sensory store = your spam folder, STM = your inbox, LTM = your organised filing system.

The Working Memory Model

Forget the simple filing cabinet idea - working memory treats STM as an active, multi-component system that actually processes information rather than just storing it.

The central executive acts like your brain's manager, monitoring incoming data and allocating tasks to three subsystems. The phonological loop handles auditory information through two parts: the phonological store (holds words you hear) and the articulatory process (allows rehearsal).

The visuospatial sketchpad processes visual and spatial information, whilst the episodic buffer temporarily integrates information from other systems and connects with LTM. Each component has different coding methods and capacities, making this model far more sophisticated than the multi-store approach.

Research supports this through dual-task performance studies and brain scanning evidence. However, psychologists still lack clarity about how the central executive actually works.

Real-world example: You can listen to music whilst doing homework because different components handle auditory and visual information separately.

Types of Long-Term Memory

Not all long-term memories are created equal - psychologists have identified three distinct types that work very differently.

Episodic memory stores personal experiences from your life, complete with time stamps. Remembering your last birthday party requires conscious effort to recall specific details. Semantic memory holds your general knowledge about the world - facts, concepts, and meanings that aren't tied to personal experiences.

Procedural memory contains your skills and actions, operating without conscious awareness. You don't actively think about how to ride a bike or tie shoelaces - these memories work automatically.

Evidence comes from case studies like Clive Wearing, who lost episodic memory but retained semantic and procedural memories. Brain scans confirm different neural areas activate for each type, and this research helps psychologists develop targeted treatments for memory problems.

Easy way to remember: Episodic = personal episodes, Semantic = school facts, Procedural = physical procedures.

Forgetting: Retrieval Failure

Ever had a word "on the tip of your tongue"? That's retrieval failure - the information exists in your memory, but you can't access it without the right cues.

Encoding specificity principle suggests memories are best retrieved when the same cues present during learning are available during recall. This creates two types of cue-dependent forgetting: context-dependent (external environment) and state-dependent (internal state of mind).

Godden and Baddeley's underwater experiment perfectly demonstrates context effects. Divers who learned word lists underwater recalled 40% less when tested on land compared to underwater. Similarly, Carter and Cassidy found participants on antihistamines recalled better when their internal state matched between learning and testing.

This explains why returning to your childhood bedroom can trigger forgotten memories, or why retracing your steps helps find lost items.

Study tip: Try revising in similar conditions to your exam environment - same room, similar temperature, even the same background noise level.

Forgetting: Interference Theory

Sometimes forgetting happens because memories literally get in each other's way, like radio stations interfering with each other's signals.

Proactive interference occurs when older memories disrupt newer ones - like struggling to remember your new phone number because the old one keeps popping up. Retroactive interference works the opposite way, with new memories disrupting older ones.

McGeoch and McDonald's research showed interference worsens when memories are similar. Participants learning word lists to 100% accuracy performed worst when the second list contained synonyms, but much better with completely different material.

Lab studies consistently demonstrate interference effects, though critics argue the artificial materials used don't reflect real-life memory situations. However, the theory explains many everyday forgetting experiences, like mixing up similar passwords or confusing details between TV shows.

Real example: Learning Spanish after studying French often creates interference - you might accidentally use French words when trying to speak Spanish.

Eyewitness Testimony: Misleading Information

Your memory of events isn't as reliable as you think - it can be contaminated and distorted by information you encounter after the fact.

Post-event discussion between witnesses can cause memory contamination, where people unconsciously adopt details from others' accounts. Gabbert's study showed 71% of participants mistakenly recalled crime details they never actually saw, picking them up through discussion with other witnesses.

Leading questions can bias eyewitness testimony in two ways. The response-bias explanation suggests question wording doesn't change memory but influences how people respond. The substitution explanation argues that misleading questions actually interfere with and distort original memories.

Loftus and Palmer's famous car crash study demonstrated this perfectly. Participants estimated different speeds depending on whether they heard "contacted" (31.8mph) or "smashed" (40.8mph) in the critical question, showing how language shapes memory recall.

Court reality: Eyewitness testimony, whilst compelling, can be surprisingly unreliable due to these psychological factors.