Memory IIIWorking MemoryAtkinson & Shiffrin (1968) Model of MemoryVisual Sensory StoreVisual Sensory MemoryIconic MemoryAtkinson & Shiffrin (1968) Model of Memorya memory test...Serial Position EffectsSerial Position EffectsEvaluating Modal Memory ModelBaddeley’s working memory model Phonological Loop(a.k.a. articulatory loop)Reading rate determines serial recallWorking memory and Language DifferencesTwo routes to phonological loopImmediate word recall as a function of modality of presentation (visual vs. auditory), presence vs. absence of articulatory suNeural Network Models of MemoryWeight-based memoryWorking Memory and Prefrontal CortexDelayed Match to Sample TasksNeural Network ModelRole of PFC in Memory EncodingMemory IIIWorking MemoryAtkinson & Shiffrin (1968) Model of MemoryVisual Sensory Store• It appears that our visual system is able to hold a great deal of information but that if we do not attendto this information it will be rapidly lost.• Sperling (1960)– Presented array consisting of three rows of four letters– Subjects were cued to report part of displayXMRJCNKPVFLBDemo at:http://www.dualtask.org/Visual Sensory Memory• Vary the delay of cue in partial report• After one second, performance reached asymptoteDelay of cue (in seconds)Mean number of words reportedIconic Memory• Sperling’s experiments indicate the existence of a brief visual sensory memory – known as iconic memory or iconic store• Information decays rapidly unless attention transfers items to short-term memory• Analogous auditory store: echoic storeAtkinson & Shiffrin (1968) Model of MemoryShort-term memory (STM) is a limited capacity store for information -- place to rehearse new information from sensory buffersItems need to be rehearsed in short-term memory before entering long-term memory (LTM)Probability of encoding in LTM directly related to time in STMa memory test...TABLECANDLEMAPLESUBWAYPENCILCOFFEETOWELSOFTBALLCURTAINPLAYERKITTENDOORKNOBFOLDERCONCRETERAILROADDOCTORSUNSHINELETTERTURKEYHAMMERSerial Position Effectsdistractor tasknodistractor task• In free recall, more items are recalled from start of list (primacy effect) and end of the list (recency effect)• Distractor task (e.g. counting) after last item removes recency effectSerial Position Effects• Explanation from Atkinson and Shiffrin (1968) model: – Early items can be rehearsed more often Æ more likely to be transferred to long-term memory– Last items of list are still in short-term memory (with no distractor task)Æ they can be read out easily from short-term memoryEvaluating Modal Memory Model• Pro: provides good quantitative accounts of many findings• Contra: – assumption that all information must go through STM is probably wrong– Model proposes one kind of STM but evidence suggests we have multiple kinds of STM storesBaddeley’s working memory modelBaddeley proposed replacing unitary short-term store with working memory model with multiple components:• Phonological loop• Visuo-spatial sketchpad• Central executive (ignore the episodic buffer)Baddeley and Hitch (1974)Baddeley (1986)Phonological Loop(a.k.a. articulatory loop)• Stores a limited number of sounds – number of words is limited by pronunciation time, not number of items• Experiment:• Word length effect – mean number of words recalled in order (list 1 Æ 4.2 words; list 2 Æ 2.8 words)LIST 1:BurmaGreeceTibetIcelandMaltaLaosLIST 2:Switzerland Nicaragua Afghanistan Venezuela PhilippinesMadagascarReading rate determines serial recall• Reading rate seems to determine recall performance• Phonological loop stores 1.5 -2 seconds worth of wordsWorking memory and Language Differences• Different languages have different #syllables per digit• Therefore, recall for numbers should be different across languages• E.g. memory for English number sequences is better than Spanish or Arabic sequences(Naveh-Benjamin & Ayres, 1986)Two routes to phonological loop VisualpresentationAuditorypresentationSpeech codePhonological loopArticulatory control process• Articulatory control process converts visually presented words into a speech code• Articulatory suppression (e.g. saying “the” all the time)– disrupts phonological loop– diminishes word length effect with visual presentation (visiospatial sketchpad takes over)Immediate word recall as a function of modality of presentation (visual vs. auditory), presence vs. absence of articulatory suppression, and word length. Baddeley et al. (1975).Neural Network Models of Memory• Long-term memory:– weight-based memory; the memory representation takes its form in the strength or weight of neural connections• Short-term memory:– activity-based memory, in which information is retained as a sustained or persistent pattern of activity in specific neural populationsWeight-based memory• Long-term associative memories can be formed by Hebbian learning: changes in synaptic weights between neurons Donald O. HebbWorking Memory and Prefrontal CortexDelayed Match to Sample Tasks• Correct response requires keeping location of food in mind.• Monkeys and humans w/lesions of PFC fail these tasks.• Infants younger than 12 months also fail versions of these tasks.Delayed Saccade Task(Goldman-Rakic)Neural Network Model• http://info.med.yale.edu/neurobio/xjwang/movie/albert/spatial_wm.htmlRole of PFC in Memory Encoding• If fMRI activity at encoding is back-sorted according to whether words are subsequently remembered or forgotten, then lower left VLPFC (and hippocampus) activation predicts later