Theory - Human memory has fascinated philosophers and thinkers for hundreds of years.
Following an earlier research by Craik and Tulving ( 1975), an experiment was designed to explore the "levels of processing" framework for human memory. It was hypothesised that the durability of the memory trace would be a positive function of the "depth" of processing, where depth referred to "greater degrees of semantic involvement"(Craik and Tulving, 1975). Twenty eight subjects were induced to process words to different depths: shallow encodings were achieved by asking questions about a word's typescript, while deep encodings were induced by asking whether a word would fit into a given category. Deeper encodings were found to be associated with higher levels of performance on the subsequent memory test than shallow ones. This result was tested using Student's unrelated t-test and found to be significant. The experiment's result appears to support Craik and Tulving's theory that retention depends critically on the qualitative nature of the encoding operations. The broader implications of these results as well as suggestions for further research are finally considered.
Introduction
Theory
Human memory has fascinated philosophers and thinkers for hundreds of years. A variety of metaphors, often of a special nature, have been used to try and capture the way memory works. Memory has been frequently thought of as a mental space in the brain: Aristotle talked of the memory as a wax tablet, Plato as an aviary and John Locke as a cabinet. More recent metaphors, inspired by technological developments, have likened memory to a telephone exchange system, to an electronic communication system and more recently to a neural network, thanks also to the new technologies of brain scanning (Fulcher, 2003)
Memory theorists appear to have been drawn into two opposing approaches. On the one hand, there were scholars such as Baddeley (1974;2000), Broadbent (1958), and Atkinson and Shiffrin (1968) who, following Ebbinghaus (1885), were keen to investigate "pure memory", i.e. the processes of encoding, storing and retrieving information, within a Stimulus-Response framework, free from any subjective interference, such as the individual's thoughts, experiences and ideas. On the other hand, there were those who, following Bartlett's pioneering work (Bartlett, 1932), were rather more concerned with the way memory was used in everyday life, how it informed our thinking and cognitive experiences and was adjusted in response to human perceptual system. Work by Craik, Lockhart, Tulving and more recently Loftus and Neisser fall within this second category (Bower, 2000).
Alongside with the proliferation of theories about different kinds of memories - short-term versus long term, visual versus auditory sensory stores, pre-categorical and post-categorical stores, episodic versus semantic, verbal versus imagery, cognitive versus motor - there has been a systematic attempt to co-ordinate these different types of memories to different parts of the brain (Bower, 2000, p.26).
Finally, more recently, Anderson's activationist model seems able to provide a unifying theoretical umbrella for the different kinds of memories mentioned above (Anderson, 1985).
Back in the late 60s it was Atkinson and Shiffrin's model , often referred ...
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Alongside with the proliferation of theories about different kinds of memories - short-term versus long term, visual versus auditory sensory stores, pre-categorical and post-categorical stores, episodic versus semantic, verbal versus imagery, cognitive versus motor - there has been a systematic attempt to co-ordinate these different types of memories to different parts of the brain (Bower, 2000, p.26).
Finally, more recently, Anderson's activationist model seems able to provide a unifying theoretical umbrella for the different kinds of memories mentioned above (Anderson, 1985).
Back in the late 60s it was Atkinson and Shiffrin's model , often referred to as the modal model, that enjoyed support and became the dominant paradigm, largely because of its relative simplicity and generality. Their formal model could make sense of several important empirical findings and was able to provide a firmer theoretical basis to the informal "two-process" approach that had inspired empirical research on memory for most of last century (Bower,2000).
Atkinson and Shiffrin explained memory as the operation of a three- store system : a sensory store, a short-term store (STS) and long-term store (LTS). They argued that when stimuli from the outside world first reach our sensory system, they are received in a short term sensory store (visual, auditory, etc.) where they are stored for a few seconds leaving an "echo" of a trace, before decaying. When stimuli traces in the sensory store are attended to and re-coded, they enter into STS. Once in STS, the information needs to be rehearsed in order to be retained or else it can be easily displaced. Rehearsal, according to Atkinson and Shiffrin, was crucial as it served the dual purpose on one hand of maintaining items in short-term store by repetition and on the other of transferring information about the items to the more permanent long-term store: "Any information in short-term store is transferred to long term store to some degree throughout its stay in the short-term store"(Atkinson and Shiffrin, 1968, p.115).
Earlier empirical research had indicated that short term memory store was of limited capacity: seven, plus or minus two appeared to be the magic number of items that could be stored in it (Miller, 1956). Endless amount of information for unlimited time could be stored in long term store instead. According to Atkinson and Shiffrin (1968), information entered the LTS through STS, thanks to continuous rehearsal; conversely, an item retrieved from LTM had to pass through STS. Rehearsal and recall were therefore identified by this model as the fundamental memory control process used by individuals. STS was assumed to act as a limited capacity working memory (Atkinson and Shiffrin, 1968).
The theory could neatly accommodate may empirical findings, among which Conrad's (Conrad, 1964) that STM uses acoustic coding while LTM is more likely to use visual coding, and that information stored in STM is displaced by new, more recent information. Rapid decaying of information stored in STM appeared also to be supported by Brown's (1958) and Peterson's (1959) findings, while Reitman's results (1974) supported some for of displacement of old information in SMS by new information.. Primacy and Recency effects in recall, first discovered by Mary Calkins (1894), but confirmed also by Murdock (1962) and Glanzer and Cumitz (1966) could be explained in terms of the number of rehearsals the item received, again as postulated by Atkinson and Shiffrin (1968). Neuropsychological evidence of amnesic patients with grossly impared LTM but normal STM and the opposite case of patients with impared STM but normal LTM seemed to strongly support a separation of LTM and STM (Baddeley, 2000)
The first serious challenge to Atkinson and Shiffrin's model first came at the beginning of the Seventies from the work of theorists such as Cermak, Craik and Lockhart, Kolers , Neisser , Paivio, Craik and Watkins and Craik and Tulving. The results of their research findings could be described, to use their own words, as a "new mini-paradigm in memory research" (Craik and Tulving, 1975).
While Atkinson and Shiffrin, constrained by their "information processing" model of human memory, had been concerned largely with structural aspects of memory , this wave of new theorists put forward a different set of assumptions which stemmed from a radically different conceptualisation of learning and retrival operations. Their criticism struck at the very heart of Atkinson and Shriffin's model: at their assumptions about the role of continuous rehearsal for maintainig items in STS and for transferring them in LTS(Baddeley, 2000).
The notion of the memory trace as "a rather automatic by-product of operations carried out by the cognitive system" functionally related to the level of cognitive processing - which Craik and Tulving put forward in 1975- represented a truly paradigmatic change (Craik and Tulving, 1975).
In their view, the memory trace was the record of operations carried out initially for the purpose of perceiving and interpreting the stimuli.Hence deeper, more meaningful analyses of perceived events would be associated with more durable memory traces than would relatively superficial analyses of the sound or appearance of incoming stimuli (Craik and Lockhart, 1972). In support of this new interpretation of the memory trace, Craik and Tulvig (1975) showed that words for which meaningful decisions are made show higher levels of retention in an incidental memory task than do the same words after decisions about their sound or appearance are made.
Since the early 70s, when it was first introduced, the "levels of processing" as a conceptual framework for the investigation of human memory has given impetus to hundreds of experiments and has been used as an "explanation" for a wide range of retention phenomena (Cermak and Craik,1979)
The experiment described below was aimed at replicating Craik and Tulving's early experiments(Craik and Tulving,1975), but on a smaller scale and in a rather simplified way. Craik and Tulving reported the results achieved in ten experiments, involving three levels of encodings - shallow, intermediate and deep - aimed at assessing not only the levels of retention in an incidental memory task, but also whether questions leading to positive responses were associated with higher retention levels than questions leading to negative responses. In 8 out of the 10 original experiments, the questions were administered individually and repeatedly, in complex combination, with individuals knowing in some cases that a recall test would be performed at the end. The results discussed here were instead obtained in an incidental learning experiment, where only two levels of encodings - shallow and deep - were induced in subjects randomly allocated to two groups, and where the simple relationship between encoding depth and recall was studied. It was hypothesised that recall performance would be a positive function of the depth of semantic involvement and that there would therefore be a difference between the "deep" , semantic group and "shallow", structural group in terms of the variables recorded (score in recall task).
