Theories Of Forgetting

Forgetting was first studied in detail by Hermann Ebbinghaus (1885/1913). He carried out numerous studies with himself as the only participant. Ebbinghaus initially learned a list of nonsense syllables having little or no meaning. At various intervals thereafter, he recalled as many of the nonsense syllables as possible. He then re-learned the list. His basic measure of forgetting was the savings method, which involved seeing the reduction or saving in the number of trials during re-learning compared to original learning. Forgetting was very rapid over the first hour or so after learning, with the rate of forgetting slowing considerably thereafter (see Figure 6.12). These findings suggest that the forgetting function is approximately logarithmic.

Rubin and Wenzel (1996) carried out a detailed analysis of the forgetting functions taken from 210 data sets involving many different kinds of learning and memory tests. Rubin and Wenzel (1996, p. 758) found (in line with Ebbinghaus, 1885), that a logarithmic function most consistently described the rate of forgetting: "We have established a law: the logarithmic-loss law." They focused on group data, but it has been confirmed (Wixted & Ebbesen, 1997) that the forgetting functions from individual participants are very similar.

How well did the logarithmic and similar functions fit the data? According to Rubin and Wenzel (1996, p. 752), "One of the biggest surprises, was how well the same functions fit different data sets, although there are exceptions, the same functions fit most data sets." The main exception was autobiographical memory (see Chapter 8). Studies on autobiographical memory differ from most memory studies in that the participants are free to produce any memory they want from their lives, and the retention interval can be decades rather than minutes or hours.

According to Baddeley (1997), the forgetting rate is unusually slow for continuous motor skills (e.g., riding a bicycle), in which individuals produce an uninterrupted sequence of responses. For example, Fleishman and Parker (1962) gave their participants extensive training in the continuous motor skills involved in a task resembling flying a plane. Even when they were re-tested after two years, there was practically no forgetting after the first trial.

Why is it important to identify the forgetting function or functions? According to Rubin and Wenzel (1996, p. 757):

There is a circular problem. Because no adequate description of the empirical course of retention exists, models of memory cannot be expected to include it. Because no current model predicts a definite form for the retention function, there is no reason for individual model makers to gather retention data to test their models.

Several theories of forgetting are discussed next. However, as Baddeley (1997, p. 176) pointed out, "We know surprisingly little about this most fundamental aspect of human memory."

Trace decay theory

Various theorists, including Ebbinghaus (1885/ 1913) have argued that forgetting occurs because there is spontaneous decay of memory traces over time. The main assumption is that forgetting depends crucially on the length of the retention interval rather than on what happens during the time between learning and test.

Jenkins and Dallenbach (1924) tested trace decay theory in a study in which two students were either awake or asleep during the retention interval. According to trace decay theory, forgetting should have been equal in the two conditions. In fact, there was much less forgetting when the students were asleep between learning and test. Jenkins and Dallenbach (1924) concluded that there was more interference with memory when the students were awake during the retention interval.

Hockey, Davies, and Gray (1972) pointed out a confounding of variables in the study by Jenkins and Dallenbach (1924). In the asleep condition, learning always occurred in the evening, whereas it mostly occurred in the morning in the awake condition. Thus, it is not clear whether forgetting depended on what happened during the retention interval or on the time of day at which learning took place. Hockey et al. (1972) unconfounded these variables. The time of day at which learning took place was much more important than whether or the participants slept between learning and test.

Minami and Dallenbach (1946) carried out a study on cockroaches, which learned to avoid a dark box. There was then a retention interval of up to 24 hours, during which the cockroaches were either active or lying inactively in a paper cone. The active cockroaches showed much more forgetting than the others, which favours an interference explanation. However, trace decay may have happened more slowly in the inactive cockroaches because of their slower metabolic rate.

There is very little direct support for trace decay theory. If all memory traces are subject to decay, it is perhaps surprising how well we can remember many events that happened several years ago and which are rarely thought about. For example, many people remembered in detail for some years what they were doing when they heard the news of Mrs Thatcher's resignation in 1990 (Conway et al., 1994; see Chapter 8).

Storing Popcorn Freezer

Speed of recall of negative childhood memories by high-anxious, defensive high-anxious, low-anxious, and repressor groups. Data from Myers and Brewin (1994).

Tips and Tricks For Boosting Your Metabolism

Tips and Tricks For Boosting Your Metabolism

So maybe instead of being a pencil-neck dweeb, youre a bit of a fatty. Well, thats no problem either. Because this bonus will show you exactly how to burn that fat off AS you put on muscle. By boosting your metabolism and working out the way you normally do, you will get rid of all that chub and gain the hard, rippled muscles youve been dreaming of.

Get My Free Ebook


Post a comment