Waugh and Norman (1965)
Aim - To investigate using a serial probe technique and support trace decay as a theory of forgetting
Procedure - A repeated measure design experiment was conducted where participants were given lists of 16 digits at a rate of one-to-four per second. The last digit, aka the probe, occured once more in the list and participants had to recall the digit which had followed it.
It was predicted that participants would recall the digit more accurately if if they were presented rapidly as their wold be less time for trace to decay, than if they were presented more slowly.
Findings - There was no relationship between speed of presentation and recall, which suggested trace decay was not a major source of forgetting in this task.
Conclusion - Forgetting is probably better explained by interference rather than decay.
Evaluation - Set out to support trace decay theory but their prediction was not supported. Keppel and Underwood also supported interference over trace decay theory. Note that both studies lack ecological validity as the tasks set were artificial and therefore may not be relevant to everyday life.
Keppel and Underwood (1962)
Aim - To investigate the effects of proactive interference on recall from memory.
Procedure - In a repeated measures design experiment, participants were given a series of trials where they had to learn trigrams (EG: TXK) and then count backwards from 3, 9 or 18 seconds (IV). The order of testing was balanced to control for order effects. The DV was the recall of the trigram.
Findings - On the first trial, performance was almost 100% even though some participants had only 3 seconds interval whilst others had 18 seconds. On the 2nd and 3rd trials, performance falls steadily as the interval increases.
If decay is the sole explanation for forgetting, performance should fall as the interval increases on the first trial as well as subsequent trials.
Conclusion - The inferior performance on later trials was due to interference; the 1st trigram learnt is remembered perfectly as there is no preceeding item to interfere. This type of interference is proactive because earlier learning of trigrams interferes with later learning.
Evaluation - This study lacks ecological validity as this situation would not arise in real life.
Yarnell and Lynch (1970)
Aim - To investigate memory loss due to concussion.
Procedure - A field study was carried out with American footballers who were concussed for a brief period of time during a game. They were approached immediatelyafter they regained consciousness and were asked for details of the events that occured in the game just prior to the injury. They were asked again 20 minutes later.
Findings - Accurate info was given when the footballers were questionned immediately after they regained consciousness, but the same information was not available 20 minutes later.
Conclusion - The consolidation process had been disrupted and therefore the information was not available in long-term store.
Evaluation - As it was a field study there was high ecological validity although ther were problems of control. EG: Is it certain they were concussed? If so, how long for? Ethical imlications also arise when questioning patients recovering from (even brief) concussion.
Godden and Baddeley (1975)
Aim - To see if cues from the environment affect recall.
Procedure - A field experiment was carried out with deep-sea divers who learnt lists of words either on land or underwater (IV). Recall of words (DV) was tested in the same or different context.
Findings - Those who learnt and recalled in different contexts (EG: learnt on land and recalled in water or vice versa) showed more than a 30% deficit compared to those who learnt and recalled in the same contexts.
Conclusion - Environmental context affects memory, and superior recall occurs when environmental conditions for learning and recalling match.
Evaluation - Although this was a field study, which means it is more ecologically valid than controlled lab experiments, the extreme conditions do not really refelct memory in everyday situations.
Glucksberg and Lloyd (1967)
Aim - To investigate otivated forgetting.
Procedure - In a repeated designs experiment participants were required to learn a paired-associate list of words (A-B). They were then asked to read a second list of words some of which were related to the B words on the paired-associate list. The related words on the 2nd list were accompanied by an unexpected and unavoidable electric shock. Participants were then asked to recall the orignial A-B list of paired-associate words (DV).
Findings - The B words which were related to the 2nd list of words learnt (accompanied by an electric shock)were forgotten significantly more often than the control words.
Conclusion - This supports the motivated theory of forgettingas the words accompanied with an electric shock would have unpleasent associations and would have been repressed.
Evaluation - There are ethical implications around the issue of deception and the use of electric shocks in this study. This is also a fairly contrived study as motivated forgetting is usually concerned with peronal and emotional events.