Most of the explanation’s on memory and forgetting are related to the cognitive processing of forgetting however interference has very little to cognitive processing. Therefore testing retroactive interference allows the experiment to be completed in a laboratory by psychologists. This it-self can be classed as artificial and criticised for its lack of ecological validity as having the experiment in a laboratory is hardly realistic and therefore can be questioned about whether it shows a true value and reliability of the results.
An experiment in a more naturalistic context was completed by Schmidt et al. (2000) involving participants who had grown up in the same area completing a questionnaire containing a map of their childhood neighbourhood. They were asked numerous questions, with the retroactive interference being the number of times they had moved away from the area. The results were as expected and there was a positive correlation between the number of times a person had moved from the area and the number of street names they could remember. This method again was criticised by many cognitive psychologists as they claimed that the taking the experiment away from the laboratories meant that you couldn’t control the variables.
Aim
- The aim of my experiment is to investigate the effects of retroactive interference on memory recall.
Null Hypothesis
- There will be no significant difference in the common number of words recalled correctly between the group that receives no retroactive interference (no second list) and the group that receives and interference word list.
Experimental Hypothesis
- The participants who do not receive an interference list will significantly recall higher average correct words than the group who received a retroactive interference word list in a free recall memory test.
- It is one tailed.
Independent Variable
The independent variable in this experiment is the interference list, which is list 2. This interference list is being used to test its effect on the recall of the primary word list.
Dependent Variable
The dependent variable in this experiment is the number of correctly recalled words remembered in a free recall memory test.
Design
The design of this experiment will be kept ethical and fair throughout; therefore all variable will have to be kept constant. This means that the participants will be split into groups at random as this will prevent demand characteristics such as practice and the order in which the participants take part in the experiment. Another advantage is that the equipment is fairly simple and therefore the experiment could take place in another environment or different conditions. Ideally the experiment would be tested on plenty of participants. However in order to keep the results reliable I have chosen to have 30 sixth-form students from Campsmount Technology College.
There are numerous reasons to why this would be appropriate. For instance all these students are of the same age, all are in further education and finally they are easily accessible and willing to take part.
Unlike the experiment in my research with McDonald and McGeoch I have decided to use only two groups instead of four. This is because I only want to test retroactive interference and therefore I only need the group who are given similar meaning words and a control group with which I can compare the results with. If I was to have the other two groups also then it would mean I was testing more than one type of interference and my variables would be much harder to control.
In the experiment I will take a list of all the students in the sixth-form willing to take part, I then randomly selected 30 participants and again randomly separated them into two groups. Group 1 is the control group and group 2 is the experimental group.
-Group 1 will be the control group and will have no interference list
-Group 2 will receive a second list with words of similar meaning
All of the 30 individuals will take the test on there own, in a room with the experimenter. Both groups will be given the primary list of words and given 30 seconds to remember as many words as possible. Group 2 will then be given a similar meaning list of words and again given 30 seconds to remember these. Once both groups have finished their individual tasks they will be given 1 minute to recall the words on the primary word list. To do this they will be asked to write them down on a recall sheet.
There are numerous variables which could affect the recall of the primary words. Firstly the main variable which could affect the reliability of the results is the room in which it takes place. The rooms available within school are limited as many will be used for lessons. Another factor would be that noise could distract the experiment. Therefore in order to eliminate this factor I need to decide on a room which is quiet and possibly away from the rest of the school. I have decided to choose the 6th form library as this room is very quiet and has little use throughout the day. I will have to use this room when the library isn’t in use and between lessons to restrict noise from the bell or corridor noise from other pupils. There are several disadvantages of having it in the library such as they is a lot of books and colourful posters in the room which could distract the attention of the participant however this overrides the fact that it is the quietest room in the school. Any distractions such as noise would affect the concentration levels of the participant and therefore would prevent the accurate recall of the primary word list.
The experiment would have to take place in this same room for all the participants in order to keep the experiment fair and reliable. Time constraints must also be kept constant; this will be achieved by using a stop watch.
Another major variable which needs to be under control is that the participants need to understand the task which they will be taking part in. If this isn’t accomplished then it could affect the results as the participant will spend time understanding the task rather than learning the words on the primary list; subsequently making the results un-reliable. Understanding the task will reduce the cognitive processing time which is valuable to this experiment. To solve this problem, prior to the experiment I will present the participants with a pre- standardised set of instructions. These will be clear and simple to understand with a step by step guide of what is expected of the participant. In order to further eliminate any confusion the participant will then be asked if they have any questions and also if there is anything they don’t understand which can then be explained verbally.
Ethical Issues
Two main ethical issues which need to be considered when doing this experiment are
1)The participant must have the right to withdraw at any time throughout the experiment. Therefore to overcome this in the briefing I explained that all participants had the right to withdraw at any time. At the end of the experiment all participants will be given a full debriefing and given the opportunity to ask any questions.
- The second issue is confidentiality; the BPS states that all participants have the right to confidentiality. In order to solve this predicament all participants will be told that all their results will be kept anonymous.
Target Audience
The participants I have chosen to use for my experiment are mixed upper sixth students at Campsmount Technology College, Doncaster, South Yorkshire. The age range will be kept to a minimum of 17-18 year olds.
The subjects will be chosen at random and therefore the proportion of male to female will not interfere with my results as I am not comparing the results of different sexes.
The type of sampling I am using is opportunity sampling. This is a method where I take a sample of the available population. It is very effective taking into account the time available and also provides results which are easy to tabulate etc.
Materials
In order to keep the experiment consistent and reliable I need to make sure all the resources are clear and constant.
- The word list
The words on the word list will be kept to:
-The same font
-The same size
-The same colour
- Between 3-6 letters long
Also the instructions will be set out clearly in-front of the participant to eliminate confusion. Accurate timing will also be in place will the aid of a stopwatch to ensure that all participant shave equal amount of time to recall the words. All this can be seen in the appendix (2a and b).
Procedure
- Randomly select 30 volunteers out of those whom consented previously.
- Check they are still willing to participate and brief them on the experiment.
- Take the willing participants into a quiet room of the library in the school’s expressive arts block.
- As the individuals attend give them a group number
- This group will be either group A or group B
- Give them the instructions and ask them if they have any questions
- The list will be placed face down in-front on the participant
- Indicate a ‘go’ for when the participant should turn the page over
- When the 30 seconds is over then indicate by saying ‘stop’.
- Take away the word list
- Now with group A participants only give then the second word list and repeat steps 7-10
- Give the participant the pen and a response sheet
- Read the instructions on the sheet and tell them they have a minute to recall their answers.
- Debrief the participants
- The experiment is then repeated with 29 other participants.
Pilot Study
A pilot was carried out under the same conditions with just 5 participants in order to see if the experiment would run smoothly. Everything went as planned and so no improvements were needed. The participants who took part in the experiment were not allowed to take part in the final experiment or confer with others.
Results
Group A is the control group which only received the first list of words to recall.
Group B is the experimental group which received both lists of words, but asked to only recall the first list on the response sheet.
Here is a copy of the raw data:
Results for the experimental group Results for the control group
I will now calculate the measures of central tendency before analysing these results as they will make the results more analytical and compare against one another.
Experimental Group
Mean: 3+8+6+5+4+4+4+2+4+3+4+6+4+3+4 = 4.27
Median: 2,3,3,3,4,4,4,4,4,4,4,5,6,6,8 = 4
Mode: 4
Range: 8-2 = 6
Standard Deviation: 1.49
Control Group
Mean: 7+6+9+9+8+10+7+9+7+9+8+8+9+10+8 = 8.27
Median: 6,7,7,7,8,8,8,8,9,9,9,9,9,10,10 = 8
Mode: 9
Range: 10-6 = 4
Standard deviation: 1.21
Here is a table showing all my results of both the interference group and the control group.
Fig (1)
Fig (2)
Standard Deviation
Here is the standard deviation calculation for the experimental group.
Summary of Results
Firstly looking at figure (1) as this shows all the central tendency and distribrution for both of my groups of participants. It includes several ways of calculating the average of a set of data including mean, median, mode, range and standard deviation.
From these results I can clearly see that control group performed the highest in the respect that they correctly recalled the most words from the first list, subsequently the experimental group scored the lowest as they recalled the least number of words.
After looking at the standard deviation I can say that the results for the control group are slightly more consistant than the experimental group because they have a lower standard deviation subsequently this shows that the data is less dispersed for the control group and works in favour of the experimental hypothesis.
Figure 2 is a graph showing the comparison between the number of correctly recalled words by the experimental group and the control group.
= control group
= experimental group
From the graph it is quite evident that the control group recalled a greater number of words than the experimental group.
Discussion
After analysising and interpretating the information in figure 1 and figure 2 I would say it is quite evident that the control group who occurred no interference had the highest levels of recall. This was shown as their mean was 8.27, this was considerable high compared to the mean of the experimental group which was only 4.27. This was also the same case in all the other measures of central tendency as shown the middle value (median) for the control group was a lot higher than that of the experimental group. The median for the control group was 8 whereas the median for the experimental group was 4. These along with the other measures of central tendency display the pattern which indicates that the interference caused some difficulty in the recall of the words for the experimental group. The results clearly support the experimental hypothesis which states that ‘The participants who do not receive an interference list will significantly recall higher average correct words than the group who received a retroactive interference word list in a free recall memory test.’ Therefore the null hypothesis is rejected and the experimental hypothesis is accepted.
The results from the experiment support the research and investigations of McGeoch and MacDonald in reference to retroactive interference as they believed that interference could take place and obstruct the recall of words previously learnt. In particular retroactive interference is where subsequent learning impedes the recall of previous learning.
An example of a naturalistic context displaying retroactive interference comes from Schmidt et al.(2000). In this experiment participants who had grown up in the same area completed a questionnaire which contained a map of their childhood area. They were asked different questions about the map, for example names of streets and how long they had lived there. The level of retroactive interference was defined by the number of times the participant had moved to other villages of cities. This was claimed because as you move you experience similar learning experiences in terms of becoming familiar to the area and streets.
When looking at limitations of this experiment I would say that the main limitation of this experiment would be the sampling technique. Although opportunity sampling is ethical and effective for collecting data within a time limit it also isn’t representative of the whole population. This was due to it being restricted to school sixth-former of a particular age and learning ability, therefore fairly restricted. All of these participants has numerous variables which could effect their performance in this experiment. For example they could be interested in psychology as a hobby and therefore totally understand the experiment and ignore the distracted(interference) task. Others may have higher IQ or remembering abilities.
In order to get a more reliable view form the whole population I would use stratified sampling however this is very time consuming and would take a lot of organisation. Another slight change I could make would be to have a pre-listed criteria for the participants before the experiment. For example a particular IQ or GCSE score. This will make my audience more concentrated and reliable for that particular group of people.
An extraneous variable that was not controlled for was the time of day that the experiment took place. Although it will not effect particular individuals in the experiment as they all had the test at the same time in the afternoon. It could have effected them in the way that they could be tired, some may have had more lessons previous than before. If I was to do the experiment again I would do the test in the morning as this seems like a more popular time of day to do the experiment as at this time no participants have had any lessons.
If I was to do this experiment again I would possible change the type of experiment in terms of possible testing retroactive interference with age. I would use different age groups and see whether age had an affect of the persons learning ability. Other variables which could be tested would be gender, male V’s females or other factors such as subject taken at a-level, intelligence or number of words in the list. However before the experiment I would definitely set a criteria so that my results are fair due to my variables being kept as constant as possible.
In conclusion to my results I believe that there was a strong possibility that retroactive interference did occur. This is because all of my results have positively supported my prediction and my experimental hypothesis, that the participants who do not receive an interference list will significantly recall a higher average correct words than the group who received a retroactive interference word list in a free recall memory test.
