Memory
Coding, Capacity and Duration
Coding: The format in which information is stored in the various memory stores
Capacity: The amount of information that can be held in a memory store
Duration
Duration: The length of time information can be held in memory
Short-Term Memory Long-Term Memory
Coding Acoustically Semantically
Capacity 7 +or-2 Unlimited
Duration 18-30 secs Lifetime
Coding
Research On Coding of STM & LTM- Baddely (1966)
Procedure:
- Baddely gave different lists of words to four groups of participants (72) to remember:
● Group 1- Acoustically similar words (e.g. cat, hat, mat)
● Group 2- Acoustically dissimilar words (e.g. pit, few, cow)
● Group 3- Semantically similar words (e.g. great, large, big)
● Group 4- Semantically dissimilar words (e.g. good, huge, hot)
- Participants were shown the words and were asked to recall them in the correct order
Results:
- When the participants had to do the recall task immediately (STM) they tended to do
worse with acoustically similar words
- When participants had to complete the recall task after 20 minutes, they tended to do
worse with semantically similar words
Conclusions:
- The STM is coded acoustically
- The LTM is coded semantically
-
Strengths Limitations
+ Lab study (high control) - Artificial tasks (lacks generalisability
to real world i.e external validity)
+ Supports assumptions of the MSM
- Lacks temporal validity (1966)
+ Use of experimental controls
- Small sample size (72= 18 per group)
, Capacity
Research On Capacity of STM- Jacobs (1887)
Procedure:
- Conducted the digit span test
- Required participants to recall a span of numbers read out to them,
increasing the amount of numbers given by one each time
- Continue until the numbers can no longer be recalled- this indicates an
individual's digit span
- Jacobs completed the same test using letters
Results:
- The mean span for digits was 9.3 items
- The mean span for letters was 7.3 items
Strengths Limitations
+ Suitable sample size (443) - Lacks temporal validity (1887)
+ Range of ages of participants (8-19) - Use of mean may include outliers the
skew data
- Early research often lacks adequate
control (may be confounding
variables)
- Artificial tasks (lack external validity)
Research on Capacity of STM- Miller (1956)
Proposal:
- Proposed concepts of chunking, suggesting grouping sets of digits or letters
into chunks allows us to recall more items
- We can recall 7 +or-2 chunks
Strengths Limitations
+ Real life application- e.g. number - Cowan (2001) disagrees, suggesting
plates and phone numbers that we can only recall about 4
chunks in the STM
- Temporal validity (1956)
, Duration
Research on Duration of STM- Peterson and Peterson (1959)
Procedure:
- 24 undergraduate students each took part in 8 trials (repeated measures)
- On each trial, participants were given a trigram (e.g. YJW)
- Participants then had to count aloud back from a given 3 digit number for a
different amount of time for each trial (either 3, 6, 9, 12, 15 or 18 seconds)- this
prevented mental rehearsal
Results:
- The trigrams were recalled with decreasing accuracy as the interval duration
increased
Strengths Limitations
+ Repeated measures reduces - Order Effects may have occurred
participant variables
- Small sample size (24)
- Age bias- all undergraduate students
- Lacks temporal validity
Research on Duration of LTM- Bharik et al (1975)
Procedure:
- Studied 392 participants in Ohio between ages 17 and 74
- School yearbooks were obtained
- Recall was tested in two ways; (1) Photo recognition test (consisting of 50
photos, some from the participants yearbook); (2) Free recall (where
participants recalled names of their graduating class)
Results:
Photo Recognition Free Recall
Within 15 Years of
90% 60%
Graduating
After 48 years Since
70% 30%
Graduating
Strengths Limitations
+ Quite a large sample size (392) - The participants ‘types’ in school may
affect the people they know (may not
+ Range of ages (17-74) have known everyone)
- Participants may have looked back
through the yearbook more recently
(confounding variables)
Coding, Capacity and Duration
Coding: The format in which information is stored in the various memory stores
Capacity: The amount of information that can be held in a memory store
Duration
Duration: The length of time information can be held in memory
Short-Term Memory Long-Term Memory
Coding Acoustically Semantically
Capacity 7 +or-2 Unlimited
Duration 18-30 secs Lifetime
Coding
Research On Coding of STM & LTM- Baddely (1966)
Procedure:
- Baddely gave different lists of words to four groups of participants (72) to remember:
● Group 1- Acoustically similar words (e.g. cat, hat, mat)
● Group 2- Acoustically dissimilar words (e.g. pit, few, cow)
● Group 3- Semantically similar words (e.g. great, large, big)
● Group 4- Semantically dissimilar words (e.g. good, huge, hot)
- Participants were shown the words and were asked to recall them in the correct order
Results:
- When the participants had to do the recall task immediately (STM) they tended to do
worse with acoustically similar words
- When participants had to complete the recall task after 20 minutes, they tended to do
worse with semantically similar words
Conclusions:
- The STM is coded acoustically
- The LTM is coded semantically
-
Strengths Limitations
+ Lab study (high control) - Artificial tasks (lacks generalisability
to real world i.e external validity)
+ Supports assumptions of the MSM
- Lacks temporal validity (1966)
+ Use of experimental controls
- Small sample size (72= 18 per group)
, Capacity
Research On Capacity of STM- Jacobs (1887)
Procedure:
- Conducted the digit span test
- Required participants to recall a span of numbers read out to them,
increasing the amount of numbers given by one each time
- Continue until the numbers can no longer be recalled- this indicates an
individual's digit span
- Jacobs completed the same test using letters
Results:
- The mean span for digits was 9.3 items
- The mean span for letters was 7.3 items
Strengths Limitations
+ Suitable sample size (443) - Lacks temporal validity (1887)
+ Range of ages of participants (8-19) - Use of mean may include outliers the
skew data
- Early research often lacks adequate
control (may be confounding
variables)
- Artificial tasks (lack external validity)
Research on Capacity of STM- Miller (1956)
Proposal:
- Proposed concepts of chunking, suggesting grouping sets of digits or letters
into chunks allows us to recall more items
- We can recall 7 +or-2 chunks
Strengths Limitations
+ Real life application- e.g. number - Cowan (2001) disagrees, suggesting
plates and phone numbers that we can only recall about 4
chunks in the STM
- Temporal validity (1956)
, Duration
Research on Duration of STM- Peterson and Peterson (1959)
Procedure:
- 24 undergraduate students each took part in 8 trials (repeated measures)
- On each trial, participants were given a trigram (e.g. YJW)
- Participants then had to count aloud back from a given 3 digit number for a
different amount of time for each trial (either 3, 6, 9, 12, 15 or 18 seconds)- this
prevented mental rehearsal
Results:
- The trigrams were recalled with decreasing accuracy as the interval duration
increased
Strengths Limitations
+ Repeated measures reduces - Order Effects may have occurred
participant variables
- Small sample size (24)
- Age bias- all undergraduate students
- Lacks temporal validity
Research on Duration of LTM- Bharik et al (1975)
Procedure:
- Studied 392 participants in Ohio between ages 17 and 74
- School yearbooks were obtained
- Recall was tested in two ways; (1) Photo recognition test (consisting of 50
photos, some from the participants yearbook); (2) Free recall (where
participants recalled names of their graduating class)
Results:
Photo Recognition Free Recall
Within 15 Years of
90% 60%
Graduating
After 48 years Since
70% 30%
Graduating
Strengths Limitations
+ Quite a large sample size (392) - The participants ‘types’ in school may
affect the people they know (may not
+ Range of ages (17-74) have known everyone)
- Participants may have looked back
through the yearbook more recently
(confounding variables)
