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Human Memory It is good to have an end to journey towards; but it is the journey that matters, in the end. Ursula K. Le Gui Memory • Process by which information is: – Acquired • Encoding – Stored in the brain • Storage – Later retrieved • Retrieval – Eventually (possibly) forgotten Information-Processing Model of Memory • Computer as a model for our memory • Three types of memory – Sensory memory – Short-term memory (STM) – Long-term memory (LTM) • Can hold vast quantities of information for many years Information-Processing Model of Memory Retrieval Stimulus Sensory memory Attention Forgetting Short-term memory Encoding Forgetting Long-term memory Forgetting Sensory Memory • Stores all the stimuli that register on the senses • Lasts up to three seconds Sensory Input Sensory Memory • Two types – Iconic memory • Visual • Usually lasts about 0.3 seconds • Sperling’s tests (1960s) – Echoic memory (we’ll come back to this) Sperling’s Experiment • Presented matrix of letters for 1/20 seconds – Report as many letters as possible • Subjects recalled only half of the letters • Was this because subjects didn’t have enough time to view entire matrix? – No • How did Sperling know this? Sperling’s Iconic Memory Experiment Sperling’s Iconic Memory Experiment Sperling’s Iconic Memory Experiment Sperling’s Iconic Memory Experiment Sperling’s Experiment • Sounded low, medium or high tone immediately after matrix disappeared – Tone signaled 1 row to report – Recall was almost perfect • Memory for images fades after 1/3 seconds or so, making report of entire display hard to do High Medium Low Sensory Memory • Echoic memory – Sensory memory for auditory input that lasts only 2 to 3 seconds • Why do we need sensory memory? Short-term Memory • Function – Conscious processing of information – Attention is the key • Limits what info comes under the spotlight of short-term memory at any given time • AKA working memory Sensory Input Sensory Memory Attention Working or Short-term Memory Memorize the following list of numbers: 18121941177614922001 Write down the numbers in order. Now, try again… 1812 1941 1776 1492 2001 Short-term Memory • Limited capacity – Can hold 7 ± 2 items for about 20 seconds – Maintenance rehearsal • The use of repetition to keep info in short-term memory • CHUNK – Meaningful unit of information – Without rehearsal, we remember 4 ± 2 chunks – With rehearsal, we remember 7 ± 2 chunks – Ericsson & Chase (1982) 893194434925021578416685061209488885687727 31418610546297480129497496592280 Long-term Memory • Once information passes from sensory to short-term memory, it can be encoded into long-term memory Retrieval Sensory Input Attention Sensory Memory Working or Short-term Memory Encoding Long-term memory Long-term memory - Encoding • Elaborative rehearsal – A technique for transferring information into longterm memory by thinking about it in a deeper way • Levels of processing – Semantic is more effective than visual or acoustic processing – Craik & Tulving (1975) • Self-referent effect – By viewing new info as relevant to the self, we consider that info more fully and are better able to recall it Long-term memory • Procedural (Implicit) – Memories of behaviors, skills, etc. • Demonstrated through behavior • Declarative (Explicit) – Memories of facts • Episodic – personal experiences tied to places & time • Semantic – general knowledge – Semantic network Semantic Networks Bus Truck Ambulance Orange House Fire Engine Fire Yellow Green Red Apples Cherry Roses Sunrise Daisies Flowers Sunsets Clouds Retrieval • Retrieval – Process that controls flow of information from long-term to working memory store • Explicit memory – The types of memory elicited through the conscious retrieval of recollections in response to direct questions • Implicit memory – A nonconscious recollection of a prior experience that is revealed indirectly, by its effects on performance Retrieval – Explicit Memory • Free-recall test – A type of explicit memory task in which a person must reproduce information without the benefit of external cues • Recognition task – A form of explicit memory retrieval in which items are presented to a person who must determine if they were previously encountered • Retrieval failure – Tip-of-the-tongue (Brown & McNeill) Retrieval – Explicit Memory • Context-Dependent Memory – We are more successful at retrieving memories if we are in the same environment in which we stored them • State-Dependent Memory – We are more successful at retrieving memories if we are in the same mood as when we stored them Retrieval – Implicit Memory • Showing knowledge of something without recognizing that we know it • Research with amnesics • Déjà vu – The illusion that a new situation is familiar • Eyewitness testimony – Eyewitness transference • Unintentional plagiarism Forgetting If we remembered everything, we should on most occasions be as ill off as if we remembered nothing. William James • Lack of encoding – Often, we don’t even encode the features necessary to ‘remember’ an object/event • Decay – Memory traces erode with the passage of time – No longer a valid theory of forgetting – Jenkins & Dallenbach (1924) Interference theory • Forgetting is a result of some memories interfering with others – Proactive interference • Old memories interfere with ability to remember new memories – Retroactive interference • New memories interfere with ability to remember old memories – Interference is stronger when material is similar Forgetting • Repression – There are times when we are unable to remember painful past events – While there is no laboratory evidence for this, case studies suggest that memories can be repressed for a number of years and recovered in therapy Memory Construction • Schema theory – Preconceptions about persons, objects, or events that bias the way new information is interpreted and recalled • Misinformation effect – The tendency to incorporate false postevent information into one’s memory of the event itself • Illusory memories – People sometimes create memories that are completely false Improving Memory • Practice time – Distribute your studying over time • Depth of processing – Spend ‘quality’ time studying • Verbal mnemonics – Use rhyming or acronyms to reduce the amount of info to be stored Improving Memory • Method of loci – Items to be recalled are mentally placed in familiar locations • Interference – Study right before sleeping & review all the material right before the exam – Allocate an uninterrupted chunk of time to one course • Context reinstatement – Try to study in the same environment & mood in which you will be taking the exam