Capacity, Duration & Encoding

• Miller (1956) proposed that the capacity of short-term memory is around seven 'items', plus or minus two.
• Miller suggested that short-term memory stores 'chunks' of information, rather than individual numbers or letters.
• The immediate digit span is supported by Jacobs (1887) who found that participants had an average span of 7.3 letters and 9.3 words.
• Peterson & Peterson (1959) conducted a laboratory experiment to investigate the duration of short-term memory.
• Peterson & Peterson had 24 psychology students recalling three-letter trigrams at different intervals (3, 6, 9, 12, 15, or 18 seconds) while counting backwards.
• Peterson & Peterson found that recall accuracy decreased as the interval increased, with only 10% of trigrams correctly recalled at 18 seconds.
• Peterson & Peterson concluded that short-term memory has a limited duration of approximately 18 seconds.
• Bahrick (1975) investigated the duration of long-term memory using 392 American university graduates.
• Bahrick showed participants photographs from their high-school yearbook. They were then given a group of names and asked to select the name that matched the photographs.
• Bahrick found that 90% of the participants were able to correctly match the names and faces, 14 years after graduating.
• Bahrick also found that 60% of the participants were able to correctly match the names and faces 47 years after graduation.
• Short-term memory has a limited capacity of 7 +/- 2 items and new information can displace old information, leading to forgetting.
• The duration of short-term memory is minimal, less than 30 seconds without rehearsal.
• Chunking is a way to improve capacity of STM by grouping items so that each group is treated as one item by the short term memory, improving recall as the overall number of ‘items’ is reduced.
• Coding can depend on the sensory organ - for vision it's called iconic and for hearing it's called echoic.
• Information can be coded/ encoded in different ways; visually, acoustically or semantically.
• Visual processing is a term that is used to refer to the brain's ability to use and interpret visual information from the world around us.
• When we encode information visually, we take note of the way it is presented, either as it appears on the page, or by colour, shape or size.
• Acoustic processing is how information that we hear is processed by the brain and attended to in memory.
• Semantic processing takes note of the meaning of the information, in order to remember it more effectively.
• Capacity in memory is how much information we can retain.
• Duration in memory is how long information can be retained for.