Referring back to the e descriptive statistics table, we can clearly see that for condition A the mean recall of words is higher than that of Condition B. However it is only 0.8 higher and the question is, is this difference meaningful? It would be illogical to accept a simple average. To progress logically a statistical rest is required for analysis of results, in order to allow adequate interpretation to evaluate the two hypotheses. In order to conduct this analysis the ‘Mann Whitney U’ test was selected. As this test would be appropriate for two conditions where the independent measures design is utilised, in which each participant is only subject to one condition.
It is also used to investigate differences between two sets of data at ordinal level, or even between data at a higher level that have been reduced to ordinal. The term ‘ordinal’ means scores that can be placed in an order. In addition, it is a suitable test for analysis of data from a small sample group. Considering all of these criteria, my investigation was suitable. As participants would either be subject to condition A or condition B (independent measures). The data retrieved was ordinal, which allowed the scores to be place din rank order, and finally as I used a small sample of ten participants for each condition, it was a considerably small sample. However even with the small sample the ‘Mann Whitney U’ test still allows us to make an accurate logical progression as to whether there is considerable difference between the results of the participants between the two groups.
I selected a statistical level of significance of .05 (5%). I selected this level as from a mathematical statistical viewpoint; this means that any particular result can only have a probability of occurring by pure chance five times out of 100, or less. This level of significance is commonly accepted as being neither too low nor too high. This level of significance allows us to prevent a Type 1 error (where the Null hypothesis is wrongly rejected) or a Type 2 error (when the Alternate Hypothesis is wrongly rejected). This level is the common level used in analysis of psychological research investigation results.
After conducting the ‘Mann Whitney U’ test, the calculated value of 26.5 was obtained (appendix f). Using the supplied table of values for a one-tailed test at a p>0.05 (5%) significance level, N1 (Number of participants subject to Condition A) =10 and N2 (Number of participants subject to condition B) =10, the critical value was found to be 27. Comparing the calculated value of 26.5, with the critical value of 27, we can see that it us less than the critical value of 27. This means tat the probability of the set of results obtained for group A have a statistical chance of occurring les than 5 times out of 100 by pure chance. This then allows us to logically progress to rejecting the Null hypothesis, and thus accept the alternate hypothesis, and derive that the greater recall in condition A was influenced by some factor other than chance.
Discussion Explanation of Findings
The findings after conducting the tests show that statistically a higher mean recall score was calculated of 6.3 words, where there is no pause between each word on the word list (condition A), as opposed to a three second pause between each word on the word list (Condition B), which has a mean recall of 5.5. There is only a difference of 0.8 between the two means, however, between the median and mode, there was no difference as both were 6. At first glance, these average’s values seem insignificant in determining differences between the two sets of data. However, with the introduction of the more reliable ‘Mann Whitney U’ statistical test, a significant statistical difference between the two groups was discovered.
This, this resulted in the alternate hypothesis that ‘the faster the reader verbally progressed through the wordlist the greater the participants ‘chunking'” being supported and the null hypotheses rejected. This states that the difference between the two groups was influenced by a factor other than chance. This ‘factor’ is perceived to be the influence of ‘chunking’. The process of grouping words, where greater grouping (chunking) occurs at a faster speed of progression through the word list. Which thus caused the difference between the two groups.
Furhter interpretation of the results reveals that both groups share a similar range of performance. AS for the particiapnats subject to Condition A there was a range of 3, and a range of 4 for participants subject to condition B. We can also establish a similar degree of variation around the mean by comparing the value of the standard deviation for the two groups. For participants subject to Condition A, there was a standard deviation of 0.64, which is close to that of participants subject to Condition B of 0.92. We can thus establish that both groups shared a similarity of performance.
On the other hand even after taking into consideration the similarity in performance, we can easily establish at first glance at the raw data( appendix C), that Condition B has a substantially weaker performance than Condition A. Although the difference was small, it was consistent and statistically relevant. Referring back to the frequency polygon in the results section and the graphs in appendix E, we can see that Condition A had a greater frequency of higher scores by observing the skewed distribution in comparison to Condition B. Thus, we can confirm that generally there were higher scores obtained in Condition A.
One possible viewpoint could be that it was the consistence of different performance in Condition B that influences the results to learn towards the interpretation that, performance in Condition B is statistically significantly different to performance in Condition A. We could say that it was due to the faster verbal profession that caused more ‘chunking’ and in turn greater recall. However, we have to be cautious and accept that there is still a chance that the performance could have been somehow influenced by another factor. Factors such as the room and events before the experiment.
Relationship to background research Referring back to the introduction, we can see that research evidence provided by Shalice states that a faster rate of progression through a word list gives better recall. Therefore, the findings from this investigation support Shalice’s research, because in this investigation it has been statistically established that the participants have greater recall when the reader verbally progresses faster through the word list. Just as Shalice looked at Waugh and Norman’s study on the serial probe technique, then decided to investigate with a faster rate of progression through the list. We can relate this structure to this investigation and the two test conditions w here one group had a faster rate of verbal progression and the other group had a lower rate of verbal progression.
Although Waugh and Norman were investigating the serial probe technique and Shalice followed up with a faster progression through the list, they were still investigating recall and thus the same concept can be applied and referred to. In addition, in reference to the introduction we can see that Miller calls this the process of ‘chunking’ in which we combine individual letters or numbers into a larger more meaningful unit.
Considering this criteria my results seem to be acceptable that the faster rate of progression caused words to be grouped together into larger more meaningful ‘units’ (chunking) as the words would sound like one word. On the other hand, as the words were said as a sentence it might have caused an extra constraint on brain power in order to split them into two ‘chunks’ which is why they might have been kept as they were and this gave the impression they were ‘chunked’
As stated in the background research it is generally accepted that STM has a limited capacity of 7+/-2 chunks, this logically demonstrates the importance of ‘chunking’ to compensate for this limited capacity. This may mean that the brain automatically attempts to chunk if it is possible or if the interpretation gives the implication to ‘chunk’. In relation to my investigation the faster rate of progression would of made it easier to ‘chunk’, as the words would begin to sound like they were together as one would which would give the interpretation to ‘chunk’ or that they are ‘chunked’. The fact that each word was read out as a sentence in condition A would mean that it would be difficult to split up words if it was possible to group two or more words into a larger more meaningful unit.
For example, if the words cat and walk for read out in a word list with no pause between them they would make the word ‘catwalk’. As Simon, stated one-syllable is not one chunk, so this would either be one ‘chunk’ as the word catwalk or two chunks as two separate words as cat walk. Thus, impossible to determine if it is two separate words, or on word. If read out with no pause the brain would accept this as one word, which would mean one chunk. Conversely, one chunk would not mean one word as if this was with a gap between the two words as stated it would result in cat walk, two chunks. Once again, in correspondence with my investigation, this demonstrates the importance of the speed of progression and supports my findings and Millers’ concept of ‘chunking’.
Limitations and Modifications
Several weaknesses did occur in my investigation. A general weakness was that all of my participants were within the 16-18 age range and were A-level students. This would not allow me to generalise my results for the general population. The factor of the age range would mean that many of the participants would have typical teenager attitudes and would just see it was ‘something to do for a laugh’ and would not be very interested in the importance of the research. The fact that I was reading out the word list meant that the participant was not very involved at all, perhaps letting the participant read out the word list instead would have given a greater degree of accuracy and experimental validity.
It was obvious that most of the participants were not very motivated. Perhaps some form of motivation such as a league table of scores and/or a prize for the participant/group with the highest recall to increase motivation. However, this kind of motivator may actually reduce the experimental and ecological validity of the research, as in real life there are no rewards for ‘chunking’ into STM. Motivation was obviously a critical issue in this investigation, and some kind of motivation is always needed to ensure participant reactivity, however, one must be cautious as to not instead end up reducing the validity of the research.
Another general problem was that there was no way to separate and control LTM effects. There is no way to know that if the participant was familiar with the words, or if certain words would act as cue words. A potential way to prevent the participant from searching or rehearsing into LTM might be to keep the participant occupied, perhaps by giving them an interference task between each for condition B to prevent rehearsal instead of a simple pause.
However, although this may be effective in preventing rehearsal and reducing LTM effects, it might also affect STM, as the extra information from the displacement task is likely to displace the words from the word list. Obviously, LTM plays an important part in retrieval as demonstrated by various studies on cue-dependant forgetting and studies with the absence of cue words and then followed up with cue words. In relation the this investigation LTM effects should be minimised but with respect to not distorting or significantly influencing STM, as it may result in a type 1 or type 2 error and thus weaken the investigations validity.
Another issue was the actual words used. Referring back to my introduction, I had stated that I decided to use words with two-syllables, as one-syllable words are very easy to remember. However, different participants could have different interpretations of the words and this is what might have influenced their recall and/or ‘chunking;’. As they might of handpicked certain words to focus their attention to.
In addition, I had randomly selected words from a dictionary, and this it would be illogical to say that none of the words could be linked at all. For example, a word like maths and the word trick could be linked into a phrase such as “maths is tricky” which might become one phrase, as the majority of the population fin maths hard/tricky etc. Perhaps a potential way to overcome this would be to select uncommon words, or even make up words that have no meaning in the English language.
However, one must take into account that as Simon established, it is very hard to define a ‘chunk’ and one-syllable is not a chunk. Although Simon did establish that word size was one of the factors associated to placing an extra constraint on memory storage and recall. Therefore, if another ‘nonsense’ word list was to be constructed this research by Simon must be taken into account. In addition, the fact that all the words would be made up would question the ecological validity of the research since they would not exist in the real world.
Finally they another factor would be that although participants were opportunistically selected and then grouped, this would mean that they knew they would be subject to a psychological experiment and would have time to interact. As each member would be escorted individually which meant the rest were left waiting. As the group became smaller and smaller, this may have caused the remaining participants to feel nervous or have some kind of feeling influenced by the group getting smaller. This may have influenced their level of motivation, as the participants who waited longer might have been more exited or more fatigued and wanted to simply ‘get it over and done with. As established motivation is a key issue. A way to control this potential limitiation would perhaps be to simply use opportunistic sampling but instead of grouping, the participants simply conduct the investigation straight away on the participant.