MEMORY ACCURACY: THEORETICAL MODELS AND EXPERIMENTAL VALIDATION
Human memory has been on many occasions compared to the operations of a computer on the basis of their multifunctional systems. Memory is critical and plays a central role in our everyday information processes. Several models of information processes have in-time being proposed. The Atkinson-Shiffrin model (1968) is the most popular is and widely used by many memory researchers. The model indicates the transfer of information from the environment into the sensory memory which is very brief that some information is forgotten before it reaches the second storage. Short-term memory is the second temporary store which is also fragile. The short-term memory is very similar to working memory responsible for higher cognitive functioning which is also temporary. Information is then finally encoded onto the long-term memory where it is assumed to be a permanent storage for longer periods. Baddeley (2000) proposed the episodic buffer as the new forth component of the working memory model. This model was initially proposed by Baddeley and Hitch (1974) with three components, the central executive assisted by the phonological loop and the visuo-sketchpad assumed to be temporary storage faculties. The episodic buffer is assumed to play a very central role of binding features into objects and it is assumed to be a temporary limited store which links all systems together for the purposes of multi-dimensional coding (Baddeley, Allen and Hitch, 2011). This was the initial role of the central executive before the addition of the episodic buffer. Their study was to investigate the assumed role of the episodic buffer. This was done by studying the effects of attentionally demanding simultaneous tasks on their ability to encode and retain both individual features and bound objects

The general understanding of human memory is that it is prone to interference which leads to people making retrieval errors from the long-term memory Brady at el (2008) demonstrated in their study that visual long-term memory has the capabilities to store large amount of objects with clear details from the image. In this study participants were asked to view pictures of 2,500 different real world objects for 3s each over the course of 5.5hours. Subsequently, they were presented with pairs of images from which they had to specify the two they had previously viewed. The objects initially viewed was to be paired with other three conditions, an object from a novel category, an object of the same basic-level category, or the same object in a different state or pose. The results recorded indicated a significantly remarkably performance of 92%, 88%, and 87%, respectively. This is evidence that participants were capable to remember the gist and particular details of the presented objects.
A year after, Brady et al (2009) conducted another study with the aim to rectify the findings of their previous study mentioned above by demonstrating that participants did not encounter change blindness with the real world objects. This can only be avoided if the participant is provided with enough encoding time on each object. Change blindness is a concept where our cognitive process makes errors due to the overuse of top-down processing (Matlin, 2008). This can be demonstrated by failing to notice a significant change that has occurred in an object or scene. A classic change blindness study was demonstrated by Simons and Levin (1998). In this current study, Brady et al recruited 6 participants from their previous study of long-term visual memory. They were presented with six real-world objects arranged in two rows of three. For each of the three trials the objects appeared for (1.2, 6 or 18 seconds). Subsequently the object reappeared and the participants had to specify if the object was the same with that had previously occupied the scene. The results recorded were very similar to that of the previous study the performance was significantly high in all three trials. Thus, results suggested that change blindness for real world objects occurs when there is less or lack of encoding time or attention given to each object. Both the above mentioned studies of Brady et al clearly illustrate the memory accuracy for visual long-term memory as very precise and accurate. However it does not provide a detailed explanation on attention whether it can lead to inattentional blindness

Yet another type of memory, autobiographical memories are episodes recollected from one self’s life which may consists of biographical facts represented from either the observer or field perspective (William, Conway and Cohen 2008). Drawing from the definition it gives rise to the claim that autobiographical memory is the same as episodic memory to some extent. The disagreement exists in the case where episodic memory reflects only the selective ways of studying the memory including the traditional and quantity based approaches and autobiographical memory, memory is the dependent variable (Matlin, 2008). Although personal memories are generally considered to be accurate, for example, names for our junior school, they can still be fallible. It has been found that previous studies of autobiographical memory has landed two contradictory themes firstly, claims that people are prone to confusion or forgets everyday events specifically when similar episodes are experienced frequently. Secondly, claims that autobiographical happenings appear to remain vivid for years (Barclay and Wellman 1986). They considered them to be difficulty to investigate due to unavailability of recorded valid events. The aim of their study was to display memories of everyday emphasising accuracy as assessed by comparing actual memory events with that for foils. Data was collected over four consecutive 1-month periods. A replica of the above study was conducted by Merckelbach, Wessel and Horselenberg (1997), their results were consistence with that of Barclay and Wellman. They found that foil’s acceptance as one self’s memory is almost a popular phenomenon. Thus, autobiographical memories can still be inaccurate in the absence of suggestions and repeated interviews.

Imagination inflation phenomenon is more similar with autobiographical memory where subjects are requested to rate their confidence on the Life Events Inventory (LEI) questionnaire if certain events occurred during their childhood (Pezdek and Eddy 2001). After two weeks subjects participated in an imagination session in which they imagined some of the events from the LEI. They later took another LEI questionnaire after the investigator claimed losing their original questionnaire. The probability of believing that the events had actually occurred was very high due to the familiarity that is enhanced by imagination. Thus it misattributes the past experience due to the repeated thinking, a non-occurred childhood events seems to be real.

Researchers have also paid attention to flashbulb memories in the studies of memory accuracy as these are correlated phenomenological. They are memories by which the subject claims for detailed and distinct vivid memories related to any extraordinary event that can last for longer periods (Talarico and Rubin, 2003). These memories are considered as unique due to their live quality and representation of a biological mechanism. The debate of the accuracy of such memories is still going and various studies have been done in this regard. One classic study of flashbulb memory was conducted by Neisser and Harsch (1992) a day after the explosion of Challenger shuttle. Students were presented with a questionnaire asking them to answer questions such as where they were? how they found out?, who was with them and what time it was?, concerning when they first heard the explosion. The same students were tested again 3years later, a confidence rater test was also conducted about the accuracy of their memory. The results indicated that 7% had a perfect recall, 68% showed a varied amounts of accurate and inaccurate details in their recall, 25% of totally inaccurate memory recall and overly they found that over 90% of the students provided memories that contained at least one major inaccuracy. It was fascinating to note that students with inaccurate memories, their confidence was just the same as the students with accurate memories. Confidence and not consistency was then assumed to be the characteristics of flashbulb memories (Talarico and Rubin 2003). The memories of most of the subjects had turned vivid and a very small percentage of the subjects stated the memory entirely in the same way. Similar methodology was applied by other researchers who also found imperfect correspondence of information and memory after hearing the explosion of Challenger. Another area of debate is the inherent nature of flashbulb memories that, it is more accurate than the autobiographical memories. However, this is still unclear from existing reproaches (Talarico et.al 2004, pp. 1119).

Memory accuracy also plays a central role in the criminal justice system concerning the issue of eyewitness testimony. It is vital that their testimonies are accurate since the criminal justice system depends on them to a great degree for prosecuting perpetrators. Evidence in criminal trials is often based upon eyewitness testimony. Wells and Olson (2002) reviewed some of the various factors on how they relate to the accuracy of eyewitness testimony or identification. There are two main variables that affect eyewitness recognition accuracy, these are system and estimator variables originally created by Wells (1978). System variables are considered to be the factors under the control of criminal system and we can safely assume that these factors are related to the retrieval memory stage. The eyewitness attempts to retrieve information from the storage (memory) and errors may occur due to the line-up test biases. Thus significantly reduce accuracy especially when the perpetrator was not present in the line-up. It is worth noting that in one study by Malpass and Devine (1984), they found out that the eyewitness genuinely believes the perpetrator is apprehended when invited for the first line-up test even when the perpetrator is not on the list. Estimator variables are those factors that cannot be controlled by the justice system and the reliability of the eyewitness can only be estimated, for example, stable witness factors (gender). The estimator variables focus primarily on the first two stages of memory (encoding and storage) since it is more directed to the eyewitness.

Misleading information also has been shown to influence eyewitness testimony and consequentially reducing their accuracy (Loftus 1975). Loftus used a film of a car accident for imaginary ban study. Participants were divided into two groups, one of the group was asked 10 questions which were in line with the film. The other group was asked exactly the same questions except from 1 question which was misleading by providing the wrong information. A week after the groups were asked again if they did see the ban?. The result shows that there were more people who gave wrong answer ‘yes’ from the group provided with the misleading question. This is evidence that misleading information can change or distort the witness testimony and hence reduced reliability. Geiselman (1985) developed a new technique ‘The cognitive interview’ to improve eyewitness testimony during interrogation and it was found to considerably increase the amount of correctly recalled testimony.

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