Chapter 6- Long term memory- structure Flashcards
LTM function
Retaining information about the past is an important function of LTM, but it’s also involved in dynamic processes.
LTM is used to understand conversations. Working memory holds a sentence in the mind, while LTM is used to assess the meanings of the words and interpret what they mean. It provides background information, so that if another person mentions a friend’s name, you know who they’re talking about.
Serial position curve
A serial position curve is created by presenting a list of words to a participant, one after another. After the last word, participants are asked to write down all of the words that they can remember. The curve plots the percentage of participants that recalled each word versus where the word was on the list
Primacy effect
Participants are more likely to remember words presented at the beginning of the sequence. The first word gets 100% of the participant’s attention, so they likely have more time to rehearse it. This can also be explained by less proactive interference- no words came before the first word
Recency effect
Better memory for stimuli presented at the end of a sequence. This is likely because recently presented words are still in STM and are therefore easy to remember. Can be explained by less retroactive interference- nothing came after the last word.
Rundus primacy effect study
Rundus studied the primacy effect by presenting participants with lists of words and telling them to repeat any word out loud in the intervals between the words. Words presented earlier to the list were rehearsed more and were more likely to be remembered later, indicating that rehearsal creates the primacy effect
Glanzer and Cunitz recency effect study
Glanzer and Cunitz presented a list of words and after the list was presented, asked participants to count backward from 30 to prevent rehearsal. This eliminated the recency effect, suggesting that it was due to storage of the last words in the STM. With a longer delay, there was poorer recall of words. This interfered with STM maintenance
Coding
The form in which stimuli are represented in the mind. There are multiple types
Mental approach to coding
Asking how a stimulus is represented in the mind- this is what we will be focusing on in this chapter
Visual coding in STM and LTM
Coding in the form of a visual image. Remembering a visual pattern in a demonstration would be visual coding in the STM, while visualizing a person or place from the past would be coding in LTM.
Auditory coding in STM and LTM
Coding in the form of sound. In STM an example is the phonological similarity effect- people misremember two letters that sound alike. LTM- when you play a song in your head
Semantic coding
Coding in the mind in terms of meaning
Wickens semantic coding study methods
Studied semantic coding in STM. In each trial, participants were presented with words related to either fruits or professions. Participants listened to 3 words, counted backward for 15 seconds, and attempted to recall the 3 words. They did this for 4 trials with different words each time.
The goal was to create proactive interference- the decrease in memory that occurs when previously learned information interferes with learning new information.
Wickens semantic coding study results
Words from the same category were presented in all trials (either all fruits or all professions). Proactive interference is demonstrated because performance decreases with each trial. When words from a different category are presented at the last trial, performance increases. This is called release from proactive interference. Placing words into categories involves the meanings of words and participants were recalling words within 15 seconds of hearing them, so this experiment represents semantic coding in STM
Sachs semantic coding study
Studied semantic coding in LTM. Participants listened to a tape recording of a passage. Their recognition memory was measured to determine if they remembered the exact wording of the sentences or just the general meaning of the passage. It was found that specific wording was forgotten but general meaning can be remembered for a long time.
Recognition memory
The identification of a stimulus that was encountered earlier, studied by Sachs. Procedure- present a stimulus during a study period and later present the same stimulus along with others that were not presented. A multiple choice exam would be an example. This is different from recall, where participants are expected to produce the correct answer.
What type of coding is most common in STM tasks?
Auditory coding is most common due to the nature of STM tasks. For example, repeating a number over and over in your mind is an example of auditory coding.
What type of coding is most common in LTM tasks?
By reading a story a week ago, you are unlikely to remember the exact wording or what the words looked like. You probably remember the general meaning, which is semantic coding. Semantic coding is most common with LTM tasks.
Patient HM
Patient HM had his hippocampus removed to treat seizures in 1953. As a result, he was no longer able to form new long term memories. His STM was intact, but he could not transfer information to LTM. This suggests that STM and LTM are controlled by separate brain regions.
Patient KF
Patient KF suffered damage to a parietal lobe in a motorcycle accident. His LTM was intact, but he had poor STM. His digit span was reduced to 2, although 5-9 is normal. The recency effect in his serial position curve was reduced.
Double dissociation for STM and LTM
With patients KF and HM, a double dissociation could be established since they had damage to different areas of the brain and opposite memory impairments. This supports the idea that STM and LTM are caused by different mechanisms that can act independently.
Ranganath and D’Esposito hippocampus study methods
The hippocampus is crucial for LTM, but researchers wanted to determine if it could hold information for short periods of time. A sample face was presented to participants, followed by a delay, then a test face was presented and participants decided whether it matched the sample face. Some participants were assigned to the novel face condition, others were assigned to the familiar faces condition.
Ranganath and D’Esposito hippocampus study results
It was found that activity in the hippocampus increases as participants are holding novel faces in memory during the delay, but activity only changes slightly for familiar faces. These results suggest that the hippocampus is involved in maintaining novel information during short delays. The hippocampus and other medial temporal lobe structures that were once thought to be involved in only LTM also play some role in STM- these functions may not be as separated as we previously thought.
Episodic memory
Memory for experiences
Semantic memory
Memory for facts
Mental time travel
The experience of traveling back in time to reconnect with events that happened in the past. When you recall an event, you typically remember many visual details and how you felt at the time, like you are reliving the experience. According to Tulving, this is the defining characteristic of episodic memory and describes it as “self knowing” or “remembering”
Why doesn’t semantic memory involve mental time travel?
Semantic memory involves accessing knowledge about the world that isn’t necessarily tied to personal experience. When we experience semantic memory, we are are accessing things we are familiar with and know about. Tulving describes semantic memory as “knowing”, and it does not involve traveling back to the past.
Patient KC
Patient KC suffered brain damage to the hippocampus and surrounding structures in a motorcycle accident. He lost his episodic memory so he can’t relive past events, however, his semantic memory is intact. For example, he knows that his brother died 2 years ago, but does not remember personal experiences like what happened at the funeral.
