As promised, here is a sample experimental report based on the hypothesis "Concentrating on a listening task affects motor performance". I must stress that this is NOT a perfect experiment - in fact I'd make several changes to it after my discussions with my students - but my main objective is to give you an example of how to write an experimental report in English. If you have any comments I welcome them.
Introduction
This study aims to discover whether or not concentrating on a listening task significantly affects simultaneous performance of a motor task. The experimental hypothesis is: “Participants concentrating on listening to music whilst sorting a pile of books will sort the books more slowly than those who complete the task without listening to music.”
The null hypothesis is: “There will be no significant difference in the time taken to sort a pile of books when participants are simultaneously concentrating on music, and when they are not”. The variable measured in this experiment is the time taken to perform a task under two different conditions, one (C2) while concentrating on a listening task and one while performing the motor task alone (control condition, C1). As different areas of the brain are involved in listening and in motor control, if it could be established whether or not listening affects competence and/or rapidity of motor activity, we would have useful information about interaction or interference between activity in different brain regions. A significant difference in the time taken to complete the task in the two conditions could indicate that regions of the brain involved in motor control are inhibited when someone is actively concentrating on listening; if there is no significant difference in the dependent variable, interference between the different areas would appear less likely.
Methods
Participants were selected from among the researcher’s friends and colleagues, of both genders and with an arbitrary age restriction of 25-60 years old, to reduce any possible unsuspected effects of age on performing the task. All had normal hearing and eyesight (with glasses if needed) and no significant motor impairment, such as arthritis. It was explained that they would be asked to sort and move a pile of books while wearing headphones, and would be timed as they did so. They were invited to ask questions, which were answered fully (there was no need to withhold any information in this experiment). They signed a consent form, specifying that data would be anonymous and they had the right to withdraw at any time before, during or after the experiment, without giving a reason.
A regular pile of 40 books, volumes of an academic journal and all alike in size, shape and weight, was placed at one end of an otherwise empty table 110cm long, with all the books face-up. Participants were asked to perform a simple motor task: sitting at the table, to take the books one by one, with their left hand if right-handed (and vice-versa) and create a new regular pile at the other end of the table with the books alternately face-up and face-down. In Condition 1 (the control condition) they did only this task; in Condition 2 they were simultaneously listening to music, and asked to indicate if the music stopped at any point during the task. Time taken to complete the task was measured in both conditions by a colleague (the ‘timer’). The independent variable was the presence or absence of the listening task, and the dependent variable the time taken to complete the motor task in the two conditions. In fact the music never stopped in Condition 2, so the only difference between the two conditions was the concentration on listening. Participants in both conditions wore headphones, for two reasons: i) to reduce possible distraction from ambient noise, a potential extraneous variable, and ii) so that the timer would not know which condition was being timed (double blind). Other potential extraneous variables, such as participant alertness, were reduced (though probably not eliminated) by having all participants perform the task at the same time of day (between 10 and 11am); other extraneous variables may not have been eliminated, as a laboratory setting was not available. All participants in Condition 2 listened to the same music (the slow movement of the Brahms Violin Concerto), always at the same volume, set very low to increase the level of listening concentration, and also so that the timer could not hear it, and thus remained unaware of the difference between the two conditions.
It was decided to use a within-participants design, with all participants doing the task in both conditions (half doing condition 1 first, and half condition 2, to counterbalance any possible order or practice effect, but in random order so that the timer was unaware which condition was being timed) and by having all participants perform the task in the same setting at the same time of day. Variables intrinsic to the participants, such as music preferences and interest in books, should also have been at least partly overcome by this design. A within-participants design should also have overcome certain potential confounding variables, such as age, manual dexterity or a habit of listening to music (or not) whilst working, since all participants carried out exactly the same motor task in both conditions, and exactly the same listening task in condition 2 – simply listening for whether the music stopped, without any modification in the motor task.
The data collected consists of the times taken by each participant to complete the motor task in the two conditions, and in a full study would be analysed using a standard t-test to assess the probability of any detected variation in the means of the two sets of times being the result of chance. After completion of the task, the new pile of books was checked by the experimenter for regularity and for errors; if the participant had failed more than twice to arrange the books as asked (alternately face-up and face-down), or if the pile was very irregular or fell over, their results were discarded.
Participants were given their instructions orally, using a written script (see below, Appendix) which was read to them in the absence of the timer, as the instructions for Condition 1 and Condition 2 are slightly different.
There is no reason to think that this experiment could expose anyone to any risk of physical or emotional harm: nothing took place during it which was not explained to them beforehand, and if they preferred not to handle books, listen to music or be timed doing so, they need not give their consent.
The only equipment needed for the experiment was a pile of 40 identical volumes, a CD player with headphones and a stopwatch. These were all shown to participants before the experiment began. As the participants were all wearing headphones, a hand signal (agreed with the timer) was used to indicate the beginning and end of the task, which participants carried out separately.
Results of pilot study
Participant Age Gender C1 C2 1st
1 39 M 1min 37sec 1min 43sec C2
C1 = time taken to complete task in Condition 1
C2 = time taken to complete task in Condition 2
1st = Condition carried out first
In a complete study involving at least twenty participants, the mean times taken in each condition would be calculated, and a standard t-test used to assess the probability of any difference in the two means being the result of chance. This would require appropriate computer software or a conversion table.
Discussion
Even with a single participant, this pilot study threw up certain unforeseen problems with the experimental design. The participant wanted to perform the task standing up the second time (he had remained seated the first time, C2), and it was clear that this would have made the task easier. His slight frustration at being asked to remain seated may have affected his result. This also led to the realisation that the length of participants’ arms would have an effect on performance: taller participants would find it easier to reach for the books. Also, the headphones did not successfully eliminate ambient noise in C1; the participant could still hear me speak with the headphones on. Another problem is that of using music for the listening task. Many people enjoy listening to music while they work, and find it increases their concentration; others find it impossible. A recorded series of neutral tones might be better, but even then it is hard to exclude the possibility of participants liking/disliking what they hear. Further reflection suggests other extraneous variables: 1) participants in C1 were not listening to music. It might be better to have all participants listening to something, but only asked in C2 to identify any change in what they hear. This means the null hypothesis also needs to be revised, as it fails to distinguish between ‘listening’ and ‘concentrating on listening’. 2) The instructions for the two conditions are slightly different – this might be a confounding variable, but it is hard to see how it could be avoided. There is also the question of a ‘regular’ pile of books; this needs to be defined or some other criterion used, as in this case the second pile of books was stable but quite ‘irregular’ – a subjective judgement on the experimenter’s part. There are still several details in this design which need to be corrected before it could be used in a full study.
Appendix – Instructions to participants:
Condition 1: [Timer is not in the room] On the table in front of you, at the right-hand end, is a regular pile of 40 books, all the same size, shape and weight, and all face-up. When you are ready I will ask you to put on these headphones, to reduce any possible noise distraction, and then take the books one by one, using only your left hand [if the participant is right-handed, or only the right hand if left-handed] and make another regular pile at the left-hand end of the table with the books alternately face-up and face-down. My colleague who is waiting outside is going to time how long it takes you to do this. There is no need to try to do the task as quickly as possible. All you have to do is re-create the pile in the way I have described, but please make the new pile as regular as the first, still using only the same hand. I will indicate when to begin the task with this hand signal [demonstrate signal agreed with colleague]. Please make the same hand signal when you have finished. Do you have any questions? [If there are no questions, or when any questions have been answered:] I am going to ask my colleague to come in now. Please put the headphones on. [Timer enters. When timer and participant are ready, make eye contact with participant and give hand signal to begin].
Condition 2: [Timer is not in the room] On the table in front of you, at the right-hand end, is a regular pile of 40 books, all the same size, shape and weight, and all face-up. When you are ready I will ask you to put on these headphones – you will hear some music. Please take the books one by one, using only your left hand [if the participant is right-handed, or only the right hand if left-handed] and make another regular pile at the left-hand end of the table with the books alternately face-up and face-down. My colleague who is waiting outside is going to time how long it takes you to do this. At the same time I want you to raise your other hand if the music you are listening to stops at any point, but don’t stop re-arranging the books. There is no need to try to do the task as quickly as possible. All you have to do is re-create the pile in the way I have described, but please make the new pile as regular as the first, still using only the same hand. I will indicate when to begin the task with this hand signal [demonstrate signal agreed with timer]. Please make the same hand signal when you have put the headphones on to indicate that you can hear the music, and at the end of the task to tell me that you have finished. Do you have any questions? [If there are no questions, or when any questions have been answered:] I am going to ask my colleague to come in now. Please put the headphones on. [Wait for hand signal to indicate music is audible. Timer enters. When timer and participant are ready, make eye contact with participant and give hand signal to begin].
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