Draw memory model on board – what has happened here? Info not gone from sensory memory to STM. Selective attention. In this case info has not passed to STM
Now where do you think encoding failure would be on model? (In between STM and LTM)
Ask for a couple of people to give data and plot all lines – draw mean through that. Bottom axis – time 3/12/18 against number recalled
Why is this the result? What happens to the memory? What do we know about STM?
Where is the trace of each memory stored? Trick question, we don’t know – remember Penfield (inconclusive evidence) and Lashey’s experiment with rats – memories don’t stay in one particular spot. Also – if memory failure is down to storage decay does memory fade at a constant rate like water running out a bath?
What else might explain this curve? Why might memory loss occur? Look at first 20 mins. Could be displacement – next slide
Which is the experiment we’ve just done
Example of fly posting – retroactive - new information can obscure old and make it difficult to retrieve, particularly if new information is similar to the old. And vice versa
‘’In the practical use of our intellect, forgetting is as important as remembering’’ William James, philosopher & psychologist
forgetting – a definition The inability to recall or recognise material which was previously stored in memory. A distinction can be made between: Lack of availability – material that was placed in memory and which has now disappeared. Lack of accessibility – material that is still in memory but cannot be recalled
why do we forget? Encoding failure Storage decay Retrieval failure Motivated forgetting
but first…a quick attention test http://www.youtube.com/watch?v=Ahg6qcgoay4&feature=related
forgetting or failure to encode? "We must never underestimate one of the most obvious reasons for forgetting, namely, that the information was never stored in the first place" Loftus
1. Failure to encode Remember that everything in short term memory is lost unless it is moved to long term memory. That isn’t so much forgetting as the failure to encode and store incoming data. Such transference to LTM requires attention and usually intention.
The Brown-Peterson experiment 1) on each trial you will see three words that you will try to remember 2) following the three words you will see a three digit number (eg. 526) 3) As soon as that number appears you are to begin silently counting backwards from that number in 3’s (eg. 526, 523, 520, 517) 4) Keep counting until you see a set of question marks. This is your cue to write down the three words you saw at the beginning of the trial 5) This same procedure will continue for several trials 6) Questions?
Scoring DOG SHIRT TREE CAR LEG MOUSE PENCIL SPOON ARM CUP TABLE SHOE BOOK CORD TOE FINGER WORD RUG SOCK WINDOW GRASS BACK COFFEE PAGE VOICE HAT PEN Find the total # you got right on the following sets of trials: 6 sec: trials 1,5,7 12 sec: trials 2,4,9 18 sec: trials 3, 6, 8
2. Storage Decay (Lack of availability) Trace Decay theory proposes that unless information in memory is regularly refreshed or used it will spontaneously begin to fade or weaken over time. This is based on the assumption that memories have a physical basis, the trace. Over time, metabolic processes break down this trace (decay) making the information unavailable. Conversely, with rehearsal, the trace becomes stronger and is less likely to be forgotten
Ebbinghaus (1885) First person to conduct systematic scientific research on forgetting Had subject memorize lists of 13 nonsense syllables Measured retention at different intervals
Ebbinghaus (1885) Ebbinghaus’s findings suggests forgetting occurs early, suggesting that the information was never properly placed in long term memory.
Evaluation of trace decay Peterson and Peterson (1959) (+) Research demonstrated that all but 10% of memories were lost after 18 seconds when rehearsal was prevented through an interference task. This is evidence that trace decay occurs within 18 seconds Low ecological validity (-) The use of nonsense trigrams and lists of numbers doesn’t represent learning in everyday life and thus findings cannot be easily generalised
But...is it trace decay or displacement? Forgetting in STM is usually attributed to the limited capacity (displacement) and duration (trace decay) of STM Displacement theory explains forgetting in terms of capacity (7 +/- 2: Miller, 1956). Once STM is full, any new information to be remembered must push out old information. The old information is forgotten Participants in Peterson & Peterson’s study were given a distractor task which might have led to interference or displacement of the original trigrams. Ideally you would study decay by having participants learn material and recall it later without doing anything in between learning and recall. However, it is difficult to prevent rehearsal without an interference task.
3. Retrieval Failure (Lack of accessibility ) Rapunzel – available but not accessible
Tip of the tongue phenomenon Memory cues or prompts can sometimes aid retrieval
Interference - a cause of retrieval failure Interference or ‘inhibition’ by other material is a common problem. Learning some items may interfere with the retrieval of another. Two types of interference: Retroactive inhibition Proactive inhibition
4. Motivated forgetting This is a type of forgetting which seems to be motivated by unpleasant events. For example, forgetting a dentist appointment Freud argued that all forgetting was motivated by an UNCONSCIOUS willingness not to remember information which is in some way uncomfortable Freudian idea of repression Traumatic events pushed below consciousness
Evaluation motivated forgetting Little empirical support for this idea If anything, traumatic events are too easily remembered: i.e., Post-traumatic Stress Disorder (PTSD)
conclusion Forgetting has several possible causes Encoding failure: the memory never gets stored Decay: the memory deteriorates and fades Retrieval failure: we just can’t find the memory Motivated forgetting: we don’t want to find the memory
Can We Trust Memory? A memory is a sheet of paper in a filing cabinet. We take it out of the file. Look at it. Edit it! And put it back. What do we take out the next time? The edited version!