Short-term Memory Experiment: What is the duration of STM?
• Recall method:
o Participants are presented with a stimuli.
o Delay of either (a) 3 seconds or (b) 18 seconds.
o Participants are asked to remember as many of the stimuli as possible.
o Memory performance is measured by the percentage of stimuli remembered.
o Participants remembered 80% of the stimuli after 3 seconds.
o Paricipants remembered 12% of the stimuli after 18 seconds.
o Participants forgot the letters because of decay.
Decay: Process by which information is lost from STM due to the passage of time.
Short-term Memory Experiment: What is the capacity of STM?
• Digit Span Method:
o Participants are given a piece of paper with series of numbers on it, starting at 4 and increasing by one on each trial.
o Look at 4 numbers, cover them and write them down.
o Look at 5 numbers, cover them and write them down.
o Look at 6 numbers, cover them and write them down.
o ETC. Until You cannot remember all of the numbers and record them accurately.
o Average Capacity : 5-9
o Magic Number = 7!
o The capacity of STM averages out at 5-9 and thus 7.
• Method: Ask person to repeat string of digits presented to them.
o Determine the length of digit span that a person can repeat without making mistakes.
o Train participant to chunk numbers based on their prior knowledge.
o Determine how many numbers they can repeat with out error.
Compare this to their score before training.
• Result: Chunking will enable the trained individual to store much more info in STM.
• Conclusion: Chunking, by virtue of its interaction with LTM, increases capacity of STM.
Auditory Coding Experiment:
• Method: (a) Briefly flash target letters on a screen.
(b) Ask participants to write down the letters that had been flashed in order.
o When participants made errors, the errors were often caused by the misidentification of the target letter as another letter that sounds like the target letter.
o Coding for letters was auditory, even though participants saw the letters.
Semantic Coding Experiment:
o Two Groups : A) Fruit Group B) Profession Group
o Four Trials.
After each trial, ask participants to immediately write down the stimuli.
o Fruit Group presented with the names of 4 fruits on each trial.
o Profession Group presented with the names of 4 professions on trials 1, 2, & 3.
On trial 4, Profession Group presented with the names of four fruits.
o Both Fruit Group and Profession Group performed strongly on trial 1.
o Fruit Group performance dropped after the 1st trial, and remained down for remaining trials.
o Profession Group performance dropped after the 1st trial.
On the 4th trial (when presented with the names of fruits) Profession Group's performance increased.
o Fruit Group had a strong performance and then dropped because of Proactive Interference.
o Proactive Interference: when information learned previously interacts with learning new information.
o Profession Group had a similar performance until, on the fourth trial when presented with the names of fruits, they were released from proactive interference.
o Participants were semantically coding information. Because:
(1) Profession Group was released from proactive interference when a set of words from a new group was presented, and
(2) because placing words into categories involves the meaning of the words
Working Memory Experiment: How Does Brain Damage to Prefrontal Cortex Affect Memory?
• Method: Delayed Response Task
o Information is provided.
o Brief delay imposed.
o Memory is tested.
Monkeys tested by letting them see where food is being hidden (under one of two cloths.)
Wait 10 seconds.
Monkey looks for reqard under one of the two cloths.
o Monkeys with healthy brain performed higher than average for remembering where food was hidden.
o Monkeys with prefrontal cortex removed performed at the level of chance guesses.
o The prefrontal cortex is important for holding information for brief periods of time.
Working Memory: Distributed Processing?
o Brain imaging experiments reveal that a large number of brain areas are involved in working memory.
Working Memory Experiment: How does the capacity and efficiency of one's WM correlate with their comprehension, reasoning ability, and intelligence?
o Reading Span method: The maximum number of sentences that a person can read while simultaneously holding the last word of each sentence in memory (and here repeating them in order).
Used to measure both storage and processing functions of working memory.
o Measure reading span for 20 individuals.
o Give participants a comprehension test where they answer questions about a paragraph.
o Collect the SAT scores of participants.
o Those who had a higher reading span tended to score better on the comprehension test and to have higher SAT scores.
o Working memory is associated with comprehension and intelligence.
(larger working memory with more efficient processing, better comprehension ability and higher intelligence.)
Long-Term Memory Experiment: What is the difference between LTM and STM?
• Serial Position Method:
o Read a list of 15 words to participants, read 1 word and wait 2 seconds.
o Without a delay, ask the participants to write down all of the words that they remember in any order.
o Analyze results by plotting the percentage of recall for each word against the words position on the list.
(create a serial position curve)
o Memory is better for words at the beginning of the list and for words at the end of the list.
(Memory is poor for words at the middle of the list.)
o Primacy effect: Superior memory for words at the beginning of the list.
Participants had the chance to rehearse these words and transfer them to LTM.
o Recency Effect: Superior memory for words at the end of the list.
The words at the end of the list are still in the participants STM.