Memory Research

Coding:

• Crowder (1993) found that the SR only retains information in the iconic store for a few milliseconds, but for two to three seconds within the echoic store, which supports the idea of sensory information being coded into different sensory stores

Capacity:

• Sperling (1960) flashed a 3x4 grid of letters onto a screen for one-twentieth of a second, and asked participants to recall the letters of one row. As the information would fade very quickly, he sounded different tones to indicate which row had to be recalled. Recall of letters in the indicated row was high, which suggests all the information was originally there, indicating that the capacity of the SR is quite large. 

Duration:

• Walsh and Thompson (1978) found that the iconic sensory store has an average duration of 500 milliseconds, which decreases as individuals get older. This suggests that duration of sensory memories is limited and dependent on age. 

Coding:

• Posner & Keele (1967) found participants were faster in assessing that ‘A’ followed by ‘A’ was the same letter than when ‘A’ was followed by ‘a’. Because the visual code differs when ‘A’ is followed by ‘a’, the findings show that visual coding was occurring, which illustrates how codes other than the acoustic one occurs in STM

Capacity:

• Miller (1956) reviewed research to find the capacity of STM to be between 5-9 items, but that the ‘chunk’ was the basic unit of STM. This means 5-9 chunks can be held at any one time, increasing the stores’ capacity. Simon (1974) found that although STM capacity should be measured in terms of chunks, this varies with the type of material being recalled and the amount of information contained within the chunks.

Duration:

• Marsh et al (1997) found that if participants weren’t expecting to have to recall information, STM duration was only between two and four seconds, which suggests duration of STM is affected by the amount of time taken to process information.

Coding:

• Frost (1972) gave participants 16 drawings in four categories (e.g. animals), differing in visual orientation, like angle of viewing perspective. The order of recall of items suggested participants used visual and semantic coding, implying evidence for a visual as well as semantic code in LTM.

Capacity:

• Wagenaar (1986) created a diary of 2,400 events over 6 years and tested himself on recall of events rather than dates, finding he too had excellent recall, suggesting the capacity of LTM is extremely large. Diary studies, however, are a type of case study and are therefore not representative of the general population and there could be an element of bias as people are testing themselves. 

Duration:

•  Goldman & Seamon (1992) asked participants to identify odours of everyday products experienced in the last two years and odours not experienced since childhood. Although identification (by name) was better for more recent odours, there was significant identification of less-recent odours, suggesting duration of olfactory (smell-based) information in LTM is very long lasting.

• Baddeley (1996) discovered participants found it difficult to generate lists of random numbers while simultaneously switching between pressing between numbers and letters on a keyboard, suggesting the two tasks were competing for CE resources. This supports the idea of the CE being limited in capacity and only being able to cope with one type of information at a time.

• Gathercole & Baddeley (1993) found participants had difficulty simultaneously tracking a moving point of light and describing the angles on a hollow letter F, because both tasks involved using the VSS. Other participants had little difficulty in tracking the light and performing a simultaneous verbal task, as both tasks involve using the VSS and the PL, indicating the VSS to be a separate slave system. 

• Baddeley et al (1975) reported on the word length effect, where participants recalled more short words in serial order than longer words, supporting the idea that capacity of the PL is set by how long it takes to say words, rather than the actual number of words.  

• Prabhakaran et al (2000) used fMRI scans to find greater right-frontal brain activation for combined verbal and spatial information, but greater posterior activation for non-combined information, providing biological evidence of an EB that allows temporary storage of integrated information. 

• Alkhalifa (2009) reported on a patient with severely impaired LTM who demonstrated STM capacity of up to 25 prose items, far exceeding the capacity of both the PL and the VSS. This suggests the existence of an EB, which holds items in working memory until they are recalled. 

Episodic LTM - Herlitz et al (1997) assessed explicit LTM abilities in 1000 Swedish participants, finding that females consistently performed better than males on tasks requiring episodic LTM, although there were no differences in semantic LTM ability. This suggests that there are gender differences in episodic memory ability, which may be explained in part by females’ generally having higher verbal ability. 

Semantic LTM - Vicari et al (2007) reported on the case study of CL, an eight-year-old girl who suffered brain damage due to the removal of a tumor. She demonstrated deficiencies in her episodic LTM functions, especially in creating new episodic memories, but was still able to create and recall semantic memories. This suggests that episodic and semantic memory are separate systems using different brain areas, with the hippocampus associated with episodic memory and the perirhinal cortex with semantic LTM. 

Procedural LTM - Finke et al (2012) reported the case study of PM, a 68-year-old professional cello player who suffered damage to various brain areas after contracting encephalitis, resulting in severe amnesia. His episodic and semantic LTM were very affected, but although he could not remember musical facts his ability to read and play music was unaffected, including the learning of new complex pieces.

McGeoch and McDonald studies retroactive interference by changing the amount of similarity between two sets of materials. Participants had to learn a list of 10 words until they could remember them with 100% accuracy. They then learned a new list. There were six groups of participants who had to learn different types of list:

1) Synonyms 2) Antonyms (words with opposite meanings as the originals) 3) Words unrelated with the original ones 4) Nonsense syllables 5) Three-digit numbers 6) No new list (these participants just rested)

When the participants then recalled the original list of words, their performance depended on the nature of the second list. The most similar material (synonyms) produced the worst recall. This shows that interference is strongest when the memories are similar. 

• Baddeley & Hitch (1977) got participants who had played in a varying number of rugby union games to remember as many of the tams that they had played against as possible. Interference theory was tested by assessing how recall was affected by the number of games played. It was found that forgetting was due to the number of games played rather than the time passed between games. Supporting interference theory.

Encoding specificity principle: Endel Tulving (1983) reviewed research into retrieval failure and discovered a consistent pattern to the findings. He summarized this pattern in what he called the encoding specificity principle. This states that if a cue is to help us recall information it has to be present at encoding and at retrieval. It follows from this that if the cues available at encoding and retrieval are different there will be some forgetting.

Context-dependent forgetting: Godden and Baddeley (1975) carried out a really interesting study of deep sea divers working underwater. In this situation its crucial – a matter of life and death – for divers to remember instructions given before diving about their work underwater.In this study the divers learned a list of words either underwater or on land and then were asked to recall the words either underwater or on land. In two of these conditions the environmental contexts of learning and recall matched, whereas in the other two they did not. Accurate recall was 40% lower in the non-matching conditions. The external cues available at learning were different from the ones at recall and this lead to retrieval failure. 

State dependent forgetting: Carter and Cassaday (1998) gave anti-histamine drugs to their participants. The anti-histamines had a mild sedative effect making the participants slightly drowsy. This creates an internal psychological state different from the ‘normal’ state of being awake and alert. The participants had to learn lists of words and passages of prose and then recall the information, creating four conditions.In the conditions where there was a mismatch between internal state at learning and recall, performance on the memory test was significantly worse. So when the cues are absent then there is more forgetting.

• Loftus and Palmer (1974) arranged for participants to watch film clips of car accidents and then gave them questions about the accident. In the critical questions (leading questions) participants were asked to describe how fast the cars were travelling: ‘About how fast were the cars going when they hit each other?’This is a leading question because the verb ‘hit’ suggests the speed the car was going. There were five groups of participants, each was given a different verb in the critical question. One group had the verb hit, the others had contacted, bumped, collided, smashed. The mean estimated speed was calculated for each participant group. The verb contacted resulted in a mean estimated speed of 31.8 mph. For the verb smashed, the mean was 40.5 mph. The leading questions biased the eyewitness recall of an event. 

• Loftus and Palmer (1974) conducted a second experiment that supported the substitution explanation – the wording of a leading question actually changes the participants’ memory of the film clip. This was demonstrated because participants who originally heard ‘smashed’ later were more likely to report seeing broken glass (there was none) than those who heard ‘hit’. The critical verb altered their memory of the incident. 

• Fiona Gabbert (2003) studies participants in pairs. Each participant watched a video of the same crime, but filmed from different points of view. This meant that each participant could see elements in the event that the other could not. For example, one one of the participants could see the title of the book being carried by a young woman. Both participants then discussed what they had seen before individually completing a test of recall. The researchers found that 71% of the participants mistakenly recalled aspects of the event that they did not see in the video but had picked up in the discussion. The corresponding figure in a control group, where there was no discussion was 0%. Gabbert et al concluded that witnesses often go along with each other, either to win social approval or because they believe the other witnesses are right and they are wrong. They called this phenomenon memory conformity. 

• Johnson and Scott (1976) led participants to believe they were going to take place in a lab study. While seated in a waiting room participants heard an argument in the next room. In the ‘low-anxiety’ condition a man then walked through the waiting area, carrying a pen and with grease on his hands. Other participants overheard the same heated argument, but this time accompanied by the sound of breaking glass. A man walked out of the room, holding a paper knife that was covered in blood. This was the ‘high-anxiety’ condition. The participants then later picked out the man from a set of 50 photos. 49% of participants who had seen the man carrying the pen were able to identify him. The corresponding figure for the people who had seen the man holding the blood-covered knife was just 33%. The tunnel theory of memory argues that a witness’s attention narrows to focus on a weapon, because it’s a source of anxiety. 

• John Yuille and Judith Cutshall (1986) conducted a study of a real-life shooting in a gun shop in Canada. The shop owner shot a thief dead. There were 21 witnesses – 13 agreed to take part in the study. The interviews were held 4-5 months after the incident and these were compared with the original police interviews made at the time of the shooting. Accuracy was determined by the number of details reported in each account. The witnesses were also asked to rate how stressed they had felt at the time of the incident, using a 7-point scale, and asked if they had any emotional problems since the event. The witnesses were very accurate in their accounts and there was little change in the amount of accuracy after 5 months – though some details were less accurate. Those participants who reported the highest levels of stress were most accurate (about 88% compared to 75% for the less-stressed group. 

• Verkampt & Ginet (2010) interviewed 229 children after a paining session, with either a CI, a SPI (standard police interview) or one of four types of MCI (modified cognitive interview), finding that the CI and MCIs were all superior to the SPI in producing accurate detail and that versions of the MCI that removed the ‘change narrative order’ component were superior, which supports that idea that MCIs are beneficial for specific types of witness.