Peterson & Peterson’s studies show that traces of memory disappeared over a period of time from short-term memory. Baddeley & Hitch and Atkinson & Shiffrin produced models of memory that state rehearsal is necessary to encode short-term memories in to longer-term memories. However, Craik & Lockhart argued that cognitive processes encode information to long-term memory and stated that ‘If the information has more meaning then it should be more memorable’.
My study sets out to test the prediction that a time delay will affect the amount of information that can be recalled from memory. The participants will be given a stimulus material to watch. Half the participants will answer questions immediately after the viewing and half after a 1-week time delay. The study was a laboratory experiment and individual group design with two groups of four female and one male answering questions on the stimulus material.
Comparisons between the free recall of information by the two group conditions were analysed and statistically tested by the Mann-Whitney test. The results suggest that less relevant information is displaced or subject to trace decay from short-term memory and more meaningful information is encoded to long-term memory over the delayed time period. The supporting theories have useful applications for student revision and memory techniques in general.
Introduction
Memory is one of the earliest areas of psychology to be studied. Ebbinghaus’ (1885/1913) conducted experiments that demonstrated that memory decreased as time increased. Although Ebbinghaus’ work can be criticised, as he was both the experimenter and the participant (and therefore, his findings could be bias) his work formed the basis of many other experiments and theories that try to understand the complex cognitive processes of memory and forgetting.
There is a general consensus among psychologists that we possess the ability to store and retrieve memories for both short and long periods of time and that there are two distinct types of memory: short-term and long-term memory. Short-Term Memory (STM) has a very limited capacity (i.e. it doesn’t hold very much) and a short duration (it doesn’t last for very long) whereas Long-Term Memory (LTM) has an unlimited capacity and duration.
Several popular models and theories of memory have aimed to explain why and how some information is encoded and stored in the short-term memory and other information undergoes a different encoding process that transfers some memories to the long-term memory. Atkinson & Shiffrin’s Multi-Store model (1968) and Baddeley & Hitch’s (1974) Working Memory Models both advocate that information is encoded in to a STM store for immediate use and encoded further and passed to the LTM store for retrieval at a later time. In both models the process of storing memories relied on rehearsal to encode the information. In contrast Craik & Lockhart (1972) Levels of Processing Theory argued that the concept of rehearsal alone is not sufficient to account for LTM and that cognitive processes operating at the time determined what is stored in LTM.
An experiment by Peterson and Peterson (1959) demonstrates the duration of STM by showing participants trigrams that they were asked to recall after a set time that increased as the experiment progressed. To prevent the participants rehearsing the trigrams they had to undertake an interference task i.e. counting backwards in three’s. They found that participants were able to recall the trigrams after 3 seconds but progressively recalled fewer as the wait time before recall increased and after 18 seconds recall was very poor. Bahrick, Bahrick & Wittinger (1975) conducted research in to Very Long-Term Memory (VLTM) that demonstrated the duration of LTM using high-school yearbooks where 90% of 392 ex-students were able to name their classmates after 34 years.
Other factors that affect the ability to encode, store and retrieve memories have been investigated, notable studies include Glanzer & Cunitz (1966) / Rundus & Atkinson (1970) that consider the serial position of information as it is received (Primacy & Recency Effect).
However, when we consider the concept of being able to remember it is easy to overlook the fact that we can also forget. The reason a memory is no longer present may not be due to the capacity or coding structure of the store (e.g. acoustic/semantic) but that the memory has been forgotten. One theory is that the memory trace simple disappears when rehearsal was prevented; this process is called the Trace Decay Theory, alternatively the task of counting backwards to prevent rehearsal may have resulted in the memory disappearing due to interference.
Waugh & Norman (1965) hypothesised that recent short-term memories were displaced by more recent pieces of information (Displacement Theory) and conducted a study using the serial probe technique. Participants had to remember a list of 16 numbers, they were then given one of the numbers (the probe) and had to state the next number in the sequence. Participants performed well if the probe was towards the end of the list but performed poorly if the probe number was towards the stat of the list. They concluded that the later numbers at the end of the list had displaced the earlier numbers in the list.