Memory Coding, Capacity and Duration

Ever wonder why you can remember song lyrics but struggle with phone numbers? That's because your brain codes information differently depending on which memory system is handling it.

Alan Baddeley's groundbreaking study showed that short-term memory (STM) stores information acoustically (by sound), while long-term memory (LTM) uses semantic coding (by meaning). When people tried to remember similar-sounding words immediately, they struggled - but after 20 minutes, they had more trouble with words that meant similar things.

Your STM capacity is surprisingly limited. Joseph Jacobs found we can typically hold about 7 items, which George Miller famously described as "7 plus or minus 2" - explaining why phone numbers and postcodes are designed the way they are! The Peterson and Peterson study revealed that without rehearsal, STM only lasts about 18 seconds.

Long-term memory duration is far more impressive. Harry Bahrick's study of high school yearbooks showed people could still recognise faces with 70% accuracy after 48 years, proving LTM can last a lifetime when the material is meaningful.

Key insight: The more meaningful information is to you personally, the better you'll remember it long-term.

The Multi-Store Model

Think of memory like a factory production line - that's essentially what Atkinson and Shiffrin's Multi-Store Model suggests. Information flows from your sensory register (which holds everything you see and hear for about half a second) into short-term memory, and finally into long-term memory through rehearsal.

The model explains why cramming doesn't work brilliantly - you need maintenance rehearsal (repeating information) to keep it in STM, and prolonged rehearsal to transfer it to LTM. Your sensory register has massive capacity but tiny duration, STM holds 7±2 items for 18 seconds, whilst LTM has unlimited capacity and duration.

Strong research support comes from studies showing STM and LTM are genuinely different - like Baddeley's acoustic vs semantic coding findings. Brain-damaged patients like KF also support this, as his digit memory was poor when heard aloud but better when read silently.

However, the model oversimplifies things. Elaborative rehearsal (linking new info to existing knowledge) is more important than just repeating things. Plus, LTM isn't one single store - it's actually multiple systems working together.

Study tip: Don't just repeat information - connect it to things you already know to get it into long-term memory more effectively.

Types of Long-Term Memory

Endel Tulving revolutionised memory research by showing that long-term memory isn't just one big storage unit - it's actually three distinct systems that handle completely different types of information.

Episodic memory is like your personal diary - it stores specific events from your life with timestamps. Remember your last birthday party? That's episodic memory at work, complete with who was there, where it happened, and how you felt.

Semantic memory works like Wikipedia - it contains general knowledge about the world that we all share. Facts like "London is the capital of England" or "fire is hot" live here. Unlike episodic memories, you usually can't remember when or where you learned these facts.

Procedural memory handles your skills and habits - riding a bike, typing, or driving. These become so automatic that you often can't explain how you do them, and trying to think about the process can actually make you worse!

Clinical evidence from patients like HM and Clive Wearing supports this division. Brain damage severely affected their episodic memory (they couldn't form new personal memories) but left their semantic knowledge and procedural skills largely intact.

Memory hack: When revising, try to engage all three systems - connect facts to personal experiences and practice applying your knowledge.

The Working Memory Model

Forget the idea that short-term memory is just a simple storage box - Baddeley and Hitch's Working Memory Model reveals it's actually more like a sophisticated multi-tasking system with several components working together.

The central executive acts like your brain's CEO, directing attention and coordinating the other components. It controls two main "slave systems": the phonological loop (handling speech and sound) and the visuospatial sketchpad (processing visual and spatial information).

The phonological loop splits into a phonological store (your inner ear) and articulatory process (your inner voice for rehearsal). The visuospatial sketchpad has a visual cache for images and an inner scribe for spatial sequences. The episodic buffer, added later, temporarily binds information from different sources.

Dual-task studies provide strong support - you can do a visual and verbal task simultaneously without much interference, but two visual tasks compete for the same system and performance drops. Patient KF's case also supports this, as his auditory digit memory was poor but visual memory remained intact.

The model's main weakness is that the central executive remains poorly understood - it's described more as what it does rather than how it actually works.

Study strategy: Use the visuospatial sketchpad and phonological loop together - read notes aloud while creating mind maps for maximum retention.

Interference Theory

Ever walked into a room and completely forgotten why you went there? Interference theory explains how competing memories can disrupt each other, causing frustrating moments of forgetfulness that we've all experienced.

Proactive interference happens when old memories mess with new ones - like when your dad keeps calling your new boyfriend by your ex's name! Retroactive interference works the opposite way, where new information disrupts older memories - perhaps struggling to remember last year's timetable after learning this year's.

McGeach and McDonald's classic study proved that similarity makes interference worse. Participants who learned synonyms after their original word list showed the poorest recall, while those learning numbers performed much better. The more similar the information, the more likely it is to get tangled up in your memory.

Real-world evidence comes from studying rugby players' memories of matches. Players who'd played more games since had worse recall of earlier matches, showing interference operates in everyday situations, not just labs.

However, Tulving and Psotka found that interference might be temporary - given the right retrieval cues, people could access "forgotten" information again, suggesting the memories weren't actually lost, just harder to reach.

Revision tip: Space out learning similar topics (like different historical periods) to reduce interference between them.

Retrieval Failure and Cues

The most frustrating thing about forgetting? Often the information is still there - you just can't find the right key to unlock it. Retrieval failure suggests that forgetting happens when we lack the right cues to access stored memories.

Tulving and Thomson's Encoding Specificity Principle explains that cues work best when they're present both during learning and recall. This creates two main types: context-dependent forgetting (external cues like location) and state-dependent forgetting (internal cues like mood or physical state).

Godden and Baddeley's underwater study dramatically demonstrated context effects - divers recalled 40% fewer words when their learning and testing environments didn't match (land vs underwater). Carter and Cassaday showed similar effects with internal states using antihistamines to make participants drowsy.

The theory has brilliant real-world applications - it explains why you might remember what you needed when you return to the original room, and supports techniques like going back to where you lost something.

However, Baddeley argues that context effects need to be quite extreme to matter in everyday life - learning in one classroom and being tested in another rarely causes problems. Also, context effects disappear with recognition tests (multiple choice) compared to recall tests (essays).

Exam strategy: Try to recreate your learning environment during revision - same location, time of day, or even background music can help trigger memories.

Cognitive Interview Techniques

Standard police interviews often fail to extract crucial details from witnesses' memories. Fisher and Geiselman's cognitive interview revolutionised criminal investigations by using psychological principles to dramatically improve eyewitness recall.

The technique uses four main strategies: First, report everything - witnesses share every detail, however trivial, as small details can trigger important memories. Second, reinstate the context - witnesses mentally return to the crime scene, imagining the environment and their emotions.

Third, reverse the order - recalling events backwards prevents witnesses from filling gaps with expectations rather than actual memories. Fourth, change perspective - describing events from another person's viewpoint disrupts the influence of schemas on recall.

The enhanced cognitive interview added elements like reducing anxiety, minimising distractions, and using open-ended questions to create better rapport between interviewer and witness.

Köhnken's research combining 55 studies found cognitive interviews produced 41% more accurate information than standard interviews. However, they also increased inaccurate details, particularly in enhanced versions, meaning police must treat the information carefully.

The main practical limitation is time and training requirements - cognitive interviews need more resources than many police forces can provide, leading some to focus on just the most effective elements.

Memory technique: Use cognitive interview principles for yourself - when trying to remember something, recreate the context and report everything that comes to mind.

Anxiety and Eyewitness Testimony

Witnessing a crime is terrifying, but does that fear help or hinder memory? Research on anxiety's effects on eyewitness testimony reveals a complicated relationship that depends on several factors.

Weapon focus effect suggests anxiety narrows attention like tunnel vision. Johnson and Scott's study showed participants were less accurate at identifying a man when he carried a bloodied knife (49% accuracy) compared to a greasy pen (33% accuracy), supporting the idea that anxiety impairs memory.

However, Yuille and Cutshall's real-world study of a gun shop shooting found the opposite - witnesses with higher stress levels were actually more accurate (88% vs 75%) even after five months. This suggests anxiety might enhance memory in genuine situations.

Pickel's research challenges the weapon focus explanation - participants were equally distracted by unexpected objects like raw chicken as by guns, suggesting surprise rather than fear causes the effect.

The Yerkes-Dodson law explains these contradictory findings with an inverted U-shaped relationship - moderate anxiety improves performance, but too little or too much impairs it. Deffenbacher's review of 21 studies supported this, showing anxiety can help or hinder depending on the level.

This has serious implications for criminal justice, as extreme anxiety during crimes might actually reduce testimony accuracy when it's needed most.

Exam insight: Remember that anxiety's effects aren't straightforward - moderate stress can actually improve your performance, but too much will hurt it.