Short term sensory store Essays

Short term sensory store Essays Short term sensory store Paper Short term sensory store Paper Sensory Memory preserves information in its original sensory form for a brief time, usually only a fraction of a second. Sensory memory allows the sensation of a visual pattern, sound or touch to linger for a brief moment after the sensory stimulation is over. In the case of vision, people really perceive an afterimage rather than the actual stimulus. Short-term Memory is a limited capacity store than can maintain unrehearsed information for about 20 to 30 seconds. In contrast, information stored in long-term memory may last weeks, months or years. Actually, you can maintain information in your short-term memory for longer than 30 seconds. How? Primarily, by engaging in rehearsal the process of verbalizing or thinking about the informationwithout rehearsal, information in short-term memory quickly decays with the passage of time. You can increase the capacity of your short-term memory by combining stimuli into larger, possibly higher-order, units called chunks. A chunk is a group of familiar stimuli stored as a single unit. The two key characteristics that originally defined short-term memory small capacity and short storage duration are still present in the concept of working memory. In certain models (Wickens (1992) being one such model), perceptual processes are conceptually separated into two stages: a short term sensory store (STSS) and perception. What these two stages have in common is the role of filtering out unnecessary information. Short Term Sensory Store (STSS) The STSS is a temporary storage mechanism associated with each sensory channel (i.e. the organs of the body responsible for touch, sight, smell, taste and hearing tactile system, eyes, nose, tongue and ears). For example, when you close your eyes an image remains in front of your (closed) eyes for a short period of time. This is referred to as iconic storage (echoic storage would be the same process of temporary storage associated with hearing). The STSS has a number of important characteristics which enable researchers to determine what constitutes temporary early processing versus deeper level processing. Firstly, the STSS is pre-attentive. This means that no conscious attention is required for something to be stored in an STSS, rather the signal/stimulus is stored in a particular STSS automatically. Secondly, the STSS is veridical. This means that the signal/stimulus is preserved in the STSS with all the physical attributes of the actual signal/stimulus. The STSS retains an exact replica of the physical attributes of the signal/stimulus. Finally, the STSS is short duration. The contents of the STSS using decay quite rapidly. The the case of iconic storage, the physical attributes of the stimulus usually decay after approximately one second, while in echoic storage the physical attributes of the signal/stimulus usually decay after approximately three seconds, and kineasthetic storage lasts approximately eight seconds. The STSS is important in cognitive ergonomics because it draws attention to the presence and the limitations of the temporary storage capacity of our sensory organs. Firstly, we must note that our sensory organs retain some memory of the signal/stimulus that enables us to perceive it without actually paying attention to it . Secondly, we must note that that each of the STSS have time-related constraints, and these constraints differ according to the sensory channel. For example, we are able to perceive visual cues from our environment even when we are not directing our conscious attention to those cues, provided that the visual cue enters the iconic storage mechanism and provided that the time interval is relatively short (approximately one second). For the most part though the STSS enables us to retain something of the signal/stimulus to allow further processing (or discarding). Perceptual Encoding Once a signal/stimulus has passed into the STSS it may be processed at progressively higher centres within the central nervous system. One theory contends that once information makes contact with a unique neural node that has previously been learned, is stored or is innate, then this information is perceived. Perception is an early information processing stage that is essentially involved with the recognition of a signal/stimuli and putting it into a category. Theorists and researchers have noted that there are different categories of perception. Absolute Judgement refers to the perceptual classification of a signal/stimulus into a particular categorical level (as is typical in absolute judgement task). This is characterised by people being asked to determine the loudness of a tone, the size of a crowd, or the smoothness of a surface. In such perception tasks, people are required to determine a single attribute. Detection is the simplest form of perception, which in essence is asking the question: is the signal/stimulus/target present or not? Pattern recognition, on the other hand is a more complex task that requires a person to perceive at least two dimensions in order to match a particular stimulus to a category. In the case of pattern recognition there is a great deal of interplay between perception and memory (long term memory in particular). Each of the combinations of the dimensions (usually referred to as features) must be compared to existing categorisations within long term memory. For example, the letters A a A a aA all fall into the category of a single alphabetic letter, despite their (slightly) different appearance. We are able to recognise the pattern and assign these letters to the same category. Finally, analogue perception is the continual perceptual categorisation of a dynamic signal/stimulus. Such perception is required when driving a car, when looking at an action movie or just walking across the street. It is important to note that perception requires some element of conscious attention in order to function. In this way, we are able to separate the roles of STSS and perceptual encoding, even although both processes are involved with the acquisition and filtering of information for higher order cognitive processing. The role of perceptual encoding in cognitive ergonomics is important for a number of reasons. Understanding when people are able to perceive a signal or not is important for many absolute judgement tasks. Whether a Doctor can see a small fracture on an X-ray, whether a security guard can detect a near invisible intruder on security monitor, or whether a quality assurance officer can see the small fault in a beer bottle top or all examples of real-world absolute judgement tasks that can benefit from our understanding of the mechanisms of absolute judgement perception. Pattern recognition can be applied to even more contexts than absolute judgement perception. Our understanding of pattern recognition has been applied to the problems of recognition of pictures, symbols (including letters or the alphabet and numbers) and icons. The large numbers of icons and pictorial symbols in computer software, on microwave ovens, on cellular phone displays and even motor vehicle dashboards demonstrates how prolific pattern recognition is within modern technological society. As these symbols are used more in society, so we are able to develop memory traces that enable us to recognise similar symbols in different situations. However, when we encounter unfamiliar symbols we can become confused and in some cases reluctant to continue.