Materials

A measure of impulsive choice was required for the present research that was simple and easy for adolescents with varied learning needs and communication difficulties to use. During the researcher’s familiarisation with pupils, it appeared many found novel tasks difficult to cope with. However, many pupils played

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computer games, and regularly swapped and tried new games, so they had experienced novelty this way. Consequently, to limit participants’ anxiety in performing a novel task and to facilitate understanding of task requirements the research team proposed the use of a simple computer game-type choice task.

The CCT (Computer Choice Task) was programmed using Visual Basic software and presented to participants (in all experiments involving the CCT) on

an Ergo® Preceptor 4 laptop (Pentium 4 processor using a Windows XP

operating system). A small number of participants presented motor control difficulties and so rather than using a keyboard, all individuals participating in studies involving the CCT used a Logitech® Attack 3 joystick to make choices towards left and right monetary rewards.

The CCT developed for the present project was named "Space Warrior". The appearance was based on that of simple traditional computer games, such as the highly popular Space Invaders game designed by Tomohiro Nishikado and released by Taito in 1978 (Bowen, n.d.). The CCT used simple, attractive graphics to deliver a number of choice options from which participants could choose between SS (Smaller Sooner) and LL (Larger Later) reward values. It was necessary for the program to interest the target population, but not to be so engrossing that it would provide an unrealistic behavioural measure of impulsive choice, and increase desire to be absent from lessons or other activity.

Participants were required to shoot one of two spaceships presented in each choice trial. One was worth a more immediately available reward value and the other was worth a fixed value that was available after a delay. Spaceship lights

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moved and a spaceship sound effect was played during each choice trial. Due to the game-like characteristics, the CCT was referred to in the brief, debrief and instructions as a "spaceship computer game". To increase visual interest, the screen picture displayed additional graphics. These included a centrally positioned moon that remained stationary whilst asteroids rotated and moved slowly around the screen, stars that twinkled (see Figure 2.1) and small rockets that flew steadily across the screen. However, these additional graphics were removed after Experiment 1 as they proved to be too distracting for participants. These additional objects never moved into the line of gun fire and they could not be shot at or hit by the gun. Headphones were also available to minimise possible external noise, however no participant used them throughout the research project as external noise was minimal.

It was considered important for the delay and reward to be both real and familiar to participants. Money is unique as a generalised conditioned reinforcer that can be exchanged for other desired items and activities. A monetary system was already in use at the school, whereby pupils received "talents" (points) that were recorded and later could be exchanged for money (1 talent was equivalent to 1 penny) and used to pay for desirable items and school activities that were approved by staff, parents or guardians. Money was therefore regarded as a reward likely to be reasonably well understood and liked by the participants. However, some members of staff at the school expressed the view that some of the boys had difficulties understanding the value of money. To facilitate understanding of the reward in the CCT, one spaceship point was equivalent to one penny. To further help participants understand reward amounts, monetary rewards were presented as figures and represented visually in a box under

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each spaceship (Figure 2.1). The appropriate number of one-penny (1p) coins were placed on the table by the side of each spaceship to additionally display the reward amount.

Figure 2.1 An example of the initial screen presentation in “Space Warrior”.

Furthermore, as the monetary reward was real and each monetary reward chosen had to be given to the participants as payment to keep, it was necessary to consider reward amounts. Given the boys' experience of earning small monetary amounts at school (between £0 and £5 each week), the reward values for each choice trial were a minimum of 0 pence and a maximum of 10 pence, as twenty trials could earn them a maximum of £2 within a single testing session. This reward amount could be covered within the research budget and

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was considered likely to be large enough that participants would not make corner solutions by choosing all SS rewards.

On starting up the program, an initial set up screen was shown where parameters could be set. A gun at the bottom of the screen was always positioned closer to the SS reward to visually represent the time to reach, shoot and be given the rewards in each choice trial (although participants were not told how long it would take to obtain each reward). For example, as can be seen in Figure 2.1, it would take longer to obtain the 10p (LL reward option) than the 5p (SS reward option).

Once a choice was made (by moving the joystick either towards the left reward or the right reward), the gun at the bottom of the screen moved slowly along the bottom of the screen to a pre-set position vertically in line with the chosen reward. The duration for the gun leaving its original position to reaching the LL reward was equivalent to the delay for that particular series of choice trials (30 seconds in Experiment 1, for example). The duration for the gun leaving its original position to reaching the SS reward was fixed at 1 second for all experiments using the CCT. The gun fired immediately when it was in position and the shot took 1 second to reach the target. The inter-trial interval was fixed at 3 seconds for all studies in which the CCT was used. In an attempt to limit the duration of the CCT and time away from routine activities, each choice was limited to 60 seconds (illustrated by a countdown timer in the middle of the screen in Figure 2.1).

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Consequently, the duration of each trial depended on whether the participant chose the LL or SS option and the amount of time they took to make each choice. For example, in Experiment 1 with a delay to the LL reward of 30 seconds, if the participant took 1 second to choose the reward, the LL choice trial would take 35 seconds (1 second to choose, 30 seconds delay to LL, 1 second to shoot the target and 3 seconds inter-trial interval), and the SS choice trial would take 6 seconds (1 second to choose, 1 second delay to SS, 1 second to shoot and 3 seconds inter-trial interval).

On completion of each series of choice trials in the main task, a screen appeared with "Great Score! Your total was:_ (Press fire to end the game)" and an audio recording saying "Great Score" was played. To ensure choice was not affected by colour preference, both spaceships were given the same colour, and spaceship colours randomly altered between each choice trial. Additionally, to control for right or left side bias, SS and LL reward options were presented randomly (as assigned by the computer program) on either side of the computer screen.

Each option presented to the participants, each choice made, and participants' response times (RTs) were recorded by the program. Two transparent containers (9cm high by 7cm diameter) were used, of which one was designated as the experimenter’s and the other as the participant’s (positioned nearest to the designated individual throughout the session). The experimenter’s container initially contained 200 one-penny coins (although this changed to 180 one-penny coins after Experiments 1 and 2) and the participant’s container was initially empty and positioned next to the laptop. The

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experimenter removed the amount of money chosen in each trial during the main task from her container and placed it into the participant’s container.

A score sheet was used to record the total monetary amounts participants obtained at each delay (similar to the form shown in Appendix M) and participants were required to sign a consent form at the beginning of the session (see Appendices D, G, J, N, R, T, X and Y). Written instructions and a brief and debrief (see Appendices E, G, H, I, J, K, L, O, S, U and Z) for the task were given to participants on a handout. They were also repeated verbally to ensure understanding.