Lesson 02 - duration

define capacity

the amount of information that can be held in a memory store

define duration

the length of time information can be held in a memory store

define coding

the format in which information is stored, may involve converting incoming information

define the sensory register

the memory stores for each of our five senses

• capacity is huge (millions of receptors)

• information lasts for a very short amount of time (less than half a second)

describe sperling’s experiment investigating sensory registers

participants saw a grid of digits and letters for 50 milliseconds. they were asked to write down 12 items or told they would hear a tone after and to write down the row indicated. when asked to report their whole thing their recall was poorer (on average 5 items were recalled, about 42%) than when asked to report one row only (3 items recalled, 75%)

this is because they were less likely they were to recall it all due to the overload of information. this suggests the information has decayed before it could all be written down, indicating a short duration

describe peterson and peterson 1959 experiment on duration of STM

24 participants were each given a consonant syllable/trigram such as YCG to remember. they were also given a 3-digit number (apart from the first trial). participants counted backwards from this number until told to stop. this prevents an mental rehearsal of the syllable (which would increase the duration of STM). on each trial participants were told to stop counting after varying periods of time and were asked to recall the consonant syllable

as the time period increased the percentage of correct responses decreased. the graph shows how more participants (around 78%) were able to recall the consonant syllable after a shorter period of time (here 3 seconds). at the halfway mark, at 9 seconds, only around 30% of responses were correct, demonstrating how this proportion dropped rapidly in the 6 second period. at 18 seconds, around 3-12% of responses were correct. this graph demonstrates the short duration of short term memory, as fresher information is more easily recalled

STM has a duration of up to 18 seconds, unless information is rehearsed

describe bahrick 1975 experiment on duration of LTM

• 392 american participants ages between 7 and 74

• used high school yearbooks

• conducted a photo recognition test - 50 photos, participants asked to pick out people they know in high school

• free recall test - participants asked to recall all the names of their graduating class

• participants tested within 15 years of graduation - 90% accurate

• participants tested after 48 years - 70% accurate

• for the free recall test, after 15 years they were 60% accurate, after 48 years they were 30% accurate

long term memory can last up to a lifetime

extraneous variables:

• how recently they have/whether they have contacted them since high school

• how well they knew them at school

• quality of photos

• how common their names are