4 STM & WM

• Memory


  1. Encoding: process of learning something

  2. Storage: process of storing info in memory system

  3. Retrieval: process of extracting stored info
• It is common for memory failure to occur at any stage
• For example, at the Retrieval stage, one may be unable to remember how to spell a word even though it is known (stored info)
• Recognition tests


  • Learning a list of words and testing to differentiate between old and new words
• Cued recall


  • Learning words in pairs and testing with a cue of one word in the pair
• Serial and Free Recall

  • Learning a list of words and testing by recalling in specific (serial) or any (free) order
• Multistore model of memory

  • Stage 1: Sensory stores
  • Stage 2: Short-Term Store (STS), Short-Term Memory (STM)
  • Stage 3: Long-Term Store (LTS)
• Sensory stores


  1. Info is stored exactly as presented for a short moment, capturing everything as seen

  2. Modality specific - haptic/touch, visual, auditory

  3. Very large capacity but items decay fast

  4. Attended info will be transferred to STM, majority of info not attended is forgotten
• Capacity of sensory stores may have been underestimated, more is seen than can be actually reported
• Visual sensory memory decays within ~500ms
• Audio sensory memory stored longer, decays after ~2s
• Short-Term Memory (STM) is memory over a short period of time, several seconds
• Participants are able to recall correctly 7 ± 2 (5-9 digits) in STM capacity tests
• STM capacity of recalling depends on the number of meaningful CHUNKS rather than the absolute amount of info
• Primary and recency effects are observed in memory recall
• Double dissociation in brain-damaged patients: some patients good on A but poor on B, and vice versa
• 7 items may be an overestimation
• Cowan’s point of view: Short-Term Memory (STM) capacity is closer to 4 (3.87)
• Primary and recency effects

  • Effects observed in memory where items at the beginning and end of a list are more easily remembered
• Double dissociation (neuropsych data)


  • Some patients perform well on task A but poorly on task B; some patients perform well on task B but poorly on task A
• Amnesic patients


  Have poor Long-Term Memory (LTM) and good Short-Term Memory (STM), experience retrograde amnesia (cannot recall past memories)
• Patients with damage to the left parieto-occipital region of the brain


  Have good Long-Term learning and recall, almost no Short-Term Memory, experience anterograde amnesia (cannot form new memories but can recall past memories before amnesia)
• Peterson & Peterson (1959): 'Duration of Short-Term store'
• Peterson & Peterson (1959)


  Subjects learn 3-letter stimulus while counting backwards by 3, after 18 seconds, ability to recall 3-letter stimulus drops to ~10%, indicating rapid forgetting of single trigram
• Rapid forgetting hypothesis 1: Decay is not the cause of forgetting from Short-Term Memory
• Rapid forgetting hypothesis 2: Interference is the cause of forgetting from Short-Term Memory
• Limitations of the multi-store model: New items interfere with previously learned or subsequently learned items
• Results show that without rehearsal of information, information in Short-Term Memory decays rapidly
• Possible interference due to the total number of trials (48 trials of 3-letters) leading to proactive interference
• Follow-up by Keppel & Underwood: Examined performance for every trial, showing a modest drop from trial 1 due to interference
• Misguided perspective: Unitary (single) store perspective considers Short-Term Memory as a subset of Long-Term Memory activated at any given time
• Similarities between Short-Term Memory and Long-Term Memory involve top-down semantic information
• Replacement of Short-Term Memory with Working Memory: System combining processing and Short-Term Memory functions (Baddeley & Hitch)
• Components of Working Memory model: Central executive, Phonological loop, Visual semantics
• Central executive


  • Most important component of the Working Memory system, responsible for deploying attentional resources, planning, coordination, inhibitory processes, problem-solving, reading, and writing
• Phonological loop


  • Holds phonological or speech information, affected by phonological similarity effect and word length effect
• Word length effect: Longer words take more time to rehearse in the phonological loop, leading to more decay
• Useful for language learning and supported by neuropsychological evidence
• When the phonological loop is disabled via articulatory suppression
• Long words


  • university
  • opportunity
  • aluminium