Within-subject design is a research method used to establish the difference within participants in differing scenarios. This method uses the same participants in both conditions. This can be advantageous as fewer participants are needed to be used to create a statistically significant result. However, exposing participants to both conditions can cause several negative consequences. Fatigue or boredom can be a common problem and affect the outcome of the study. With an increase of boredom a participant may be more likely to make more mistakes in the latter study irrespective of the independent variable. For example, the participant may become slower in the second trial testing reaction speed due to feeling tired not due to the IV. Another negative effect of using participants in the same study is the impact of the practice effect. This explains that participants get better at a particular test for example, and will therefore get improve their score in next test. This would lead to the wrong conclusions being drawn about the effect of a variable. Another effect cause by using the same participants multiple times is the same study is the carry over effect. This explains that the effect of an earlier condition affects the participant in the subsequent one. One example of this is using a within-subjects design in a study to investigate the effect of alcohol on reaction speeds. In the first condition, participants could be subjected to 8ml of alcohol and later 16ml (or vice versa), in the later condition they have receive a total of 21ml therefore this may be investigated investigate and not the 8 or 16ml (Howitt and Crammer, 2009). The obvious alternative to this is a between-subjects design. This method researches the difference between groups of participants. Participants are randomly assigned into differing conditions. For example, Loftus (1979) had two separate conditions to evaluate the effects of anxiety on memory. Participants were assigned to either a condition of high anxiety, where they overheard a heated argument and observed somebody leaving the room holding a paper knife and blood on their shirt. The other participants were exposed to a situation of low anxiety, they head a discussion and man leaving with a pen and grease on his shirt. The comparison of these groups indicates that high anxiety situations would decrease correct recall. Between subject-design are not affected by the practice effect, carryover effect and fatigue however there are some disadvantages. There may be variance in participants in different group, in the Loftus study example those in the high anxiety group may just have poorer memory skills. However, this can be counterbalanced by the use of random allocation and matched pairs. In conclusion both designs are useful, if only one could be chosen I would argue within subjects design is more likely to truly investigate whether there is an independent variable affects the dependent variable due to continuity of participant involvement across conditions. Nevertheless, a research method which incorporates both designs would be the better choice. The experiment we took part in using SAFMEDS used both within subject and between subjects design. This balances out the disadvantages of both designs and the findings collected could show the improvement individually and collectively.