The Idea of Trace Decay - Research Paper Example

The Idea of Trace Decay INTRODUCTION Since Ebbinghaus (1885) first generated the forgetting curve, stating how fast individuals tend to forget learnt information, the causes of forgetting have been continuously investigated. Human mind can forget things in several different ways and for different purposes based on different theoretical explanations. Of the many explanations suggests that the crucial factor determining forgetting is the passage of time in decay theory, and number of interpolated events in interference theory. The question whether forgetting over time is due to the passage of time or number of retroactive stimuli (interference) has been therefore of great theoretical interest, but the answer is still not clear. The idea of trace decay as a cause of forgetting may be the most obvious way to describe the forgetting curve, which suggested that memory trace tend to fade and disappear over time, it will eventually be lost if the information is not retrieved or rehearsed. The early view of distinction between shot-term and long-term forgetting was that short-term forgetting resulted from trace decay and long-term forgetting resulted from interference (Brown, 1958; Peterson & Peterson, 1959; Melton, 1963). The classic studies of Brown (1958) and Peterson and Peterson (1959) have been used as evidence for rapid rate of information decay in short-term memory, participants were asked to recall trigrams (three letters, e.g. HLM), followed by a number such as 492. The retention interval was filled by counting backwards in threes to prevent rehearsal of the memorandum. The findings showed that the longer the interval delay the less trigram were recalled, and suggested that information was lost from short-term memory from trace decay. Subsequent work moved to examine the decay in the forgetting of verbal memory. The majority of researches on verbal memory have been on recall of words or verbal stimuli. Investigators have focused more on recognition task as compared to decay and interference as causes of forgetting (Monsell, 1978; Boneau and Daily, 1992). McKone (1995) tested decay in implicit memory for words by using lexical decision task. The result showed that when the lag interval increased, lexical decision time increased. Even though the evidence supporting trace decay is equivocal, the motivation for subjects to rehearse or refresh the memoranda is removed. Subjects were asked to make a decision whether they had encountered a stimulus previously in a particular context. Baddeley and Scott (1971) stated the reason for little or no forgetting in the first trial would be due to the absence of a noisy background that lead to easy trace discrimination, therefore the trace decay was masked by ceiling effect. Baddeley and Scott tested 424 subjects in a single Brown-Peterson trial with delays up to 36 seconds. Each subject received a 3, 5, or 7 item list, and the ceiling effect was avoided. Proactive interference could not cause forgetting in this study, because there were no previous trials. The result showed a clear evidence of decay that items in short-term memory decay if they are not rehearsed. This result was refuted by Neath (1971), who found a model that was able to fit the data reported by Baddeley and Scott (1971) and showed the same results through interference. Therefore, the data was not able to provide good evidence that memory decay was based on time. During the twentieth century, the dominant approach to forgetting was interference theory. The notion of forgetting as a consequence of trace decay was almost universally rejected. There were numerous criticisms against decay theory, and the evidence included the slowing down of forgetting during sleep suggesting that, if decay is a natural result of the passage of time alone, it should be equal forgetting during sleep and wakefulness (Ekstrand, 1972). Furthermore, Waugh and Norman (1965) contrasted forgetting on the basis of trace decay and on the basis of interference. An experiment called the Probe-digit procedure was conducted in which participant were presented with lists of 16 spoken digits at the rate of 1 to 4 per second, the last digit, known as the probe, occurred exactly once before in the list and the task was to recall the digit which had followed it. If the time-decay process were important, then the chances of recalling the digit should be lower with slow than with fast presentation. The results showed that there was slightly (but not significantly) higher recall with fast than with slow presentation when the probe was near the beginning of the list. Thus, the major determiner of performance was the number of intervening items. However, the results of the study also suggested that forgetting was caused by interference from distracting elements (Keppel & Underwood, 1962; McGeoch & Irion, 1952; Jenkins & Dallenbach, 1924; Waugh & Norman, 1965). The fact that individuals possess a remarkable ability to remember pictures they have seen before has been proven by recognition tests along with recall tests (Pezdek, 1987). It has been found that visual information is received as a series of fixations, snapshots with basic durations between about 100 and 500 milliseconds (Porter, Staub, Rado & O’Connor, 2002). It has been suggested that, individuals viewing a scene 80 milliseconds earlier might face difficulty in recognizing alterations in the features of a scene indicating that little information is preserved from one glimpse to the next (Rensink, O’Regan, & Clark, 1997, 2000). On the other hand, meaningful pictures that have been observed for as little as 1 or 2 s are remembered for extended periods, provided that the recognition test does not contain new pictures (distractors) that are extremely similar to the to-be remembered old pictures (Nickerson, 1965; Potter & Levy, 1969; Shepard, 1967; Standing, 1973). At the same time, when pictured scenes are presented more quickly, in an order that reproduces successive fixations with durations of 125–333 milliseconds; majority of the pictures cannot be recognized after the sequence (Potter & Levy, 1969). In regards to gender differences in the visual forgetting memory, previous literature suggests that males have an advantage over females in recognizing pictures. At the same time, Davies and Robertson (1993) suggested that males clearly recognized more photographs of objects that were of an interest as compared to females, whereas females tended to recognize more photographs that were of their interest. In the present study, the procedure of continuous recognition task, constructed by Shepard and Teghtsoonian (1961), was used. Each item appeared twice with a varying number of delays between the two occurrences. Subjects were required to respond to every item whether it was new or has been presented in earlier sequence. If a subject remembered an item, he would correctly recognize it as ‘old’, The results showed that the probability of correct classification of old items as ‘old’ decreased when the number of intervening presentation increased, and the probability of reporting a new item as ‘old’ was not constant over the series of items but increased through the task. The shape of the false alarm curve indicated the subjects tended to adjust their response bias to match the objective probability of an old stimulus. However, guess is always an issue, the change of guessing an item will be 50%. In the study of Mandler.et al (1969) mentioned that the scores of recognition (96%) was much higher than those of recall (38%), thus the rate of guessing should always be considered. How should target and noise be distinguished? A model of recognition memory, named as Signal detection theory, stated that subjects make judgments on items based on the strength of familiarity. When subjects correctly reported a presented item as ‘old’, it was known as a hit but when a seen item was not detected by subjects, it was a miss. Furthermore, for every new item, when the subjects incorrectly reported as ‘old’, it was called false alarm. Finally, by correctly reporting a new item as new, it was known as a correct rejection. The true detection can be calculated by subtracting the proportion of the number of false alarms from the proportion of correct detections (Hits). Two measurements were produced by Signal detection theory, is d prime (reflects the sensitivity of the detector) and β beta (reflects the criterion adopted by subjects). The current study aims to investigate whether forgetting memories shows evidence of decay for pictures in continuous recognition task. This will be done by having all participants examine a series of pictures of doors and decide whether the subjects have seen it on the earlier pictures or not. There are 7 difference delays: 2, 4, 8, 16, 32, 64, and 128 intervening pictures. However, two groups will be asked to examine the same sequence of stimuli but with varied interval duration. For the present research, both decay and interference theories have been used to explain the forgetting in forgetting memory, but evidences often emphasized the importance of interference as a cause of forgetting rather than trace decay. It is predicted that the probability of correctly calling an old item "old” will decline with both increasing number of intervening pictures and the passage of time. According to the trace decay theory, the chance of recognizing the picture would be lower with longer interval duration than with shorter interval. It is predicted that subjects do better in the shorter interval group. However, in terms of the interference theory, the change of recognizing the picture would not show difference between two groups, because the same sequence of pictures was used in both conditions. The gender issue has also been considered in the present research. Previous studies have stated that males did better in recognizing pictures than females. The study also aims to investigate whether there is a significant difference between males and females in recognizing pictures. Read More