1a. Coding, capacity, duration of memory

What is memory?

Memory= the ability to be able to learn, store and later retrieve new information

What is short-term memory (STM)?

STM= The limited-capacity memory store. In STM, coding is mainly acoustic (sounds), capacity is between 5 and 9 items on average, duration is about 18 seconds

What is long-term memory (LTM)?

LTM= The permanent memory store. In LTM, coding is mainly semantic (meaning), it has unlimited capacity and can store memories for up to a lifetime

What is duration?

Duration=  The length of time information can be held in memory- before it is no longer retrievable due to memory trace decay

What is capacity?

Capacity= The amount of information that can be held in a memory store

What is coding?

Coding=The format in which information is stored in the various memory stores

What is encoding?

Encoding= the way that information is converted so that it can be stored in the memory. Information enters the brain via the senses and it is then stored in various forms, such as visual, acoustic or semantic codes

What is the method, results and conclusions for Peterson and Peterson’s research on the duration of STM?

Method, results and conclustions for Peterson and Peterson’s research on the duration of STM=

• Method=tested the STMS of 24 undergraduate students across 8 trials in which they were given a consonant syllable of 3 letters along with a 3-digit number. The ppts were then asked to count backwards from the number for 3 seconds, to prevent the rehearsal of the letters during the retention period and then to recall the 3 letters. This was repeated with longer retention intervals, going up in multiples of 3 seconds to a total of 18.

• Results= at 3 seconds, the percentage of correct responses was about 90%, dropping only to 2% after 18 seconds

• Conclusion= STM has a very short duration when verbal rehearsal is prevented

What is the method, results and consultations for Bahrick et al research on the duration of LTM?

Methods, results and conclusions for Bahrick et al’s research on the duration of LTM=

• Method= tested the LTMs of 392 ppts aged 17-74 on their recall of the names of their friends in school. Each ppt was given 2 tests

  • photo recognition test where the ppts were shown 50 pictures of their graduating year and asked to remember the names of the people

  • the free recall test was where the ppts were just asked to remember as many names as they could from their graduating class

• Results= in the photo test there was a 90% accuracy rate for those that were up to 15 years after graduating and a 70% accuracy rate for those above 48 years. in the free recall test, the accuracy were between 60% and 30%

• Conclusion= LTM can last for decades and is associated with visual coding

What is involved in Miller’s research on the capacity of STM?

George Miller (1956) made observations of everyday practice. For example, he noted that things come in sevens: seven notes on the musical scale, seven days of the week, seven deadly sins, etc. Miller thought that the span (i.e. capacity) of STM is about 7 items, plus or minus 2. But he also noted that people can recall fi ve words as easily as they can recall fi ve letters. We do this by chunking – grouping sets of digits or letters into units or chunks.

What is involved in Margaret and Peterson’s research on the duration of STM?

Margaret and Lloyd Peterson (1959) tested 24 students in eight trials each (a ‘trial’ is one test). On each trial the student was given a consonant syllable (such as YCG) to remember. They were also given a 3-digit number. The student counted backwards from this number until told to stop. The counting backwards was to prevent any mental rehearsal of the consonant syllable (which would increase the duration of STM memory for the syllable). On each trial they were told to stop after varying periods of time: 3, 6, 9, 12, 15 or 18 seconds (the retention interval). The findings were similar to the student data on the left . Aft er 3 seconds, average recall was about 80%; after 18 seconds it was about 3%. Peterson and Peterson’s findings suggested that STM duration may be about 18 seconds, unless we repeat the information over and over (i.e. verbal rehearsal).

What was involved in Baddeley et al’s research on the encoding of STM AND LTM?

Alan Baddeley (1966a, 1966b) gave diff erent lists of words to four groups of participants to remember:

• Group 1 (acoustically similar): words sounded similar (e.g. cat, cab, can).

• Group 2 (acoustically dissimilar): words sounded diff erent (e.g. pit, few, cow).

• Group 3 (semantically similar): words with similar meanings (e.g. great, large, big).

• Group 4 (semantically dissimilar): words with different meanings (e.g. good, huge, hot).

Results= STM condition resulted in worst recall of acoustically similar words due to the interference of coding. LTM condition resulted in the worst recall of semantically similar words due to the interference of coding.

Different sounds so more distinct, so best recall in STM condition → group 2

Different meanings so more distinct, so best recall in LTM condition → group 4