Background One theory developed by psychologists working within the biological approach is the idea that males have better spatial ability than females. Spatial ability is the ability to mentally manipulate 2-dimensional and 3-dimensional figures. One way in which spatial ability can be operationalised is in the form of mental rotation test. A mental rotation test requires participants to identify rotated versions of a target stimulus. Mental rotation usually takes place in the right cerebral hemisphere, in the areas where perception also occurs.
Mental rotation can be separated into the following cognitive stages (Johnson 1990): 1) Create a mental image of an object 2) Rotate the object mentally until a comparison can be made 3) Make the comparison 4) Decide if the objects are the same or not 5) Report the decision. See below for an example. Shepard and Metzler (1971) have identified sex differences in performance on mental rotation tasks. Males perform better than females (faster and making less mistakes). For this piece of research a quasi experiment is conducted because the variable that makes one group different from the other is gender i. . one condition will be male and the other condition will be female. Since gender is something that cannot be altered, the groups are pre-determined by their biological sex, therefore making it a naturally occurring variable. Any experiment that involves the investigation of a variable like the effect of gender on behaviour is called a quasi experiment because the conditions to which participants are assigned is based on a natural phenomenon. In a quasi experiment the independent variable is decided by something beyond the experimenter’s control.
The aim of this study is to conduct a partial replication of Shepard and Metzler (1971)) research in order to investigate whether sex differences exist between males and females for spatial ability. The research question is: ‘Do males have better spatial ability than females? ’ Based on previous research the experimental one-tailed hypothesis is: ‘Males complete mental rotation tasks more quickly than females’. A one-tailed hypothesis of difference is predicted because of previous findings. The Null Hypothesis is: ‘There will be no difference between the performance of males and females on a mental rotation task’.
Operationalising the variables The independent variable is naturally occurring and is simply whether the participants is male or female. Spatial ability, the dependent variable, will be operationalised using a simple mental rotation task. Participants will be required to mentally rotate pictures of objects in order to match each picture with one of six other pictures that show objects mentally rotated in a different position. Participants (10 males and 10 females) will be required to choose the correct match from a selection of six different possibilities. There will be ten separate trials.
The ten trails of each participant will be timed, in seconds, and an average time calculated for the completion of each trial. See figure 2 before for an example. Participants: 20 participants took part in the study. They were recruited using an opportunity sample. This method of sampling simply involves asking people to take part who are easily available at the time of study. In this case it was a collection of year 12 and 13 psychology students from three different classes. 10 females and 10 males took part ranging in age from 16-18 year. To follow ethical guidelines full informed consent was obtained from each participant.
This detailed the purpose of the study and explained that all results would be kept entirely confidential and participants could withdraw from the study at any point. Participants could withhold their results from the mental rotation task if they wished. Controls Because the study is a laboratory experiment, controls can be put in place to prevent confounding variables affecting the results. It is therefore possible to be more confident that any difference between the results of the males and females is only due to their gender. Controls in this experiment included ensuring that all participants undertook the task in silence.
All participants took the test in the same school computer lab and at the same time of day (Between 1:00 and 2:00pm). All participants were of a similar age and all participants did exactly the same task. Participants were seated a desk apart so they could not copy each others answers. Design As there are two groups of different participants, one male and one female, to compare times between groups the research design is an independent groups – each participants is only in one group (condition). Procedure A pilot study was conducted with 5 students not taking part in the study.
This enabled the researchers to check the timings involved in administering the mental rotation test and also to check that everything ran smoothly. The study also enabled the researchers to perfect the wording of the standardised instructions. For the main study 10 male participants sat at separate desks in the computer room with the mental rotation programme loaded. Participants read and signed a consent form. The experimenter then read from a standardised set of instructions explaining the procedure and giving permission for participants to begin the 10 mental rotation trails when they were ready.
Sitting next to each participant was a research assistant on hand to time the task. In their own time participants began the task – matching a 2D object with one of six other mentally rotated objects. This was completed in silence. After all participants had taken part a full debrief was read out to all participants, explaining the details of the research. All participants were told they could review the findings when the data had been analysed. Results The mean score (measured in seconds) for each participant can be seen below. The mean is one measure of central tendency.
If a sensitive value because all scores are taken into however this may cause the value to be skewed if there are outlying values. The mean time to complete each mental rotation trial for males was 5. 84 seconds compared to 7. 73 seconds for females. This means that males completed each on average 1. 89 seconds faster than their female counterparts. This data is represented in a visual form in the graph below which shows an observable difference between males and females. Inferential statistics To test whether there is a significant difference between the sets of scores an inferential statistical test needs to be undertaken.
This tests the probability of whether the difference between males and females is due to chance or whether the difference is due to the independent variable. An inferential statistical test is used to test the significance of the results, which will indicate whether to accept or reject the null hypothesis. Inferential statistics will indicate the probability that the results are due to chance. If the probability of the results being due to chance is high you cannot reject the null hypothesis and must assume that there is no difference between the spatial ability of males and females.
However if the probability that the results are due to chance is very low (say 5% or P < 0. 05) you can reject the null hypothesis and therefore accept the experimental hypothesis and thus assume that there is a real significant difference between the spatial abilities of males and females. When doing an inferential statistical test on the data one must select the appropriate test. To do this you must look at: 1) the type of data collected (level of measurement), 2) the research design of the experiment and 3) whether the research is looking for a difference or a relationship (correlation) between sets of data.
For this experiment the correct test to use is a Mann-Whitney test because 1) the data gathered is ratio data, 2) the research design is independent groups and 3) we’re looking for a difference between sets of scores for two different groups of participants. The results of our Mann Whitney Test produced a U value of 19. 5. Because this is less than the critical value (23) from the statistical table the results are significant. Therefore the null hypothesis is rejected and the experimental hypothesis is accepted. This means that we have found support for the idea that males do have better spatial ability than females, but it does not prove it.
The results are due to a real effect of the independent variable on the dependent variable. Conclusion One can conclude from the above research that males perform mental rotation tasks more quickly than females. The experimental hypothesis is accepted ‘Males complete mental rotation tasks more quickly than females’. However this conclusion should be considered in light of the issues described below. Issue of Validity The mental rotation is not really a true reflection of how we normally use spatial information in everyday life e. g. when driving, writing and many other everyday activities.
As such this experiment may be considered to be low in ecological validity. The test is not a particularly realistic test of spatial ability as the mental rotation task is only looking at one very specific type of spatial ability. Validity may also be questioned because of the controlled, artificial setting used. Participants knew that their performance was being monitored and this may have influenced their behaviour. Males are possibly more competitive when they know they are being watched which may explain why males performed better than females. (There may be more of a social facilitation effect for males compared to females).
Other threats to validity may come from demand characteristics i. e. males may respond more to demand characteristics that females or males may respond more to experimenter effects than females. All these alternative explanations as to why males may perform better than females threaten the validity of the study. Reliability Each person who took part in the study had their spatial ability measured using the same test scored in exactly the same way, so the internal reliability (consistency) is good. The findings are externally reliable in the sense that they produced a consistent finding to that of previous research.
The fact that the study can be easily replicated, partly because it is a laboratory study, means that the reliability can be tested. Generalisability Only having 10 participants in each group all of whom are between 16 and 18 years of age and from Enfield, is not a broad enough sample to make generalisation about populations beyond the sixth form where the study took place. A larger more representative sample is needed to be able to make more confident generalisations to a wider population. Since all students are studying A-levels they do not represent the academic abilities of all students and hence the sample is not fully representative.
Credibility The overall credibility of the experiment may be questioned as the research took place in an artificial setting and the results could have been the result of where and how the experiment was conducted rather than the result of the difference between males and females in terms of spatial ability. Because the experiment may have validity issues plus problems with generalisation caused by the limited and unrepresentative sample many psychologists would argue that the results lack credibility. More evidence may therefore be needed to support the hypothesis that males have better spatial ability than females.