Jumping bomb task

This is an original task designed to train sustained attention, the maintenance of fixation, peripheral vigilance/monitoring of cues without inducing a gaze shift, and the time discrimination. This task draws on a number of functions not engaged by the other tasks. It was introduced in the second training session onwards.

After the ITI and fixation period a bomb appears at one of the randomly selected outer target locations, that is 10 degrees off centre at 1, 3, 5, 7, 9, or 11 o’clock. It will then jump in either a clockwise or anticlockwise direction to an adjacent location a minimum of 1 and a maximum of 4 times (the number of jumps is randomly selected). After 1 to 4 jumps in either a clockwise or anticlockwise direction the direction of movement will reverse. The participant’s objective is to look at the central fixation location until the bomb jumps in the reverse direction.

There are three intervals of importance in this task:

1.) The duration of time that the distractor bombs appear for. For the full duration of training this was set to 500ms, however it can be altered. Reducing this duration will place increased processing demands on the system, and increasing this duration will place greater demands on sustained attention and vigilance.

2.) The duration for which a penultimate distractor bomb appears. It always

appeared for a duration longer than the other distractor bombs that proceeded it. Its role was to act as a cue for the imminent arrival of the target bomb. The salience of

160

this cue is a function of its absolute duration and relative duration with respect to the proceeding distractor bombs. When initially presented to participants the duration of the penultimate bomb was 650ms, that is, 150ms longer than the other distractor bombs. This was reduced across trials to a minimum of 550ms, meaning participants would need to notice a disparity in temporal durations of 50ms to pre- empt the arrival of the target bomb.

3.) The response window within which participants had to respond. The target bomb, which jumped in the opposite direction to the proceeding bombs, was visible for the duration of the response window. Any movement away from the central fixation cross greater than 30mm before the target bomb's appearance resulted in a failed trial. Failure to make a saccade to the target location within the target

duration period also resulted in a failed trial. The duration of the response window was the difficulty parameter used in the tracking version of the task, and was altered in the levelling version of the task as participants improved their RTs.

In addition to the response window, and the size of the temporal disparity between the distractor bombs and the penultimate bomb was altered as a difficulty

parameter. A third difficult parameter that was changed after two training sessions was the removal of radioactive signs on the distractor bombs. The removal of this radioactive sign made the task more difficult as it increased the visual similarity of the distractor and target bomb.

The strength of the jumping bomb task is that lapses in attention are penalised. It requires a high level of vigilance to firstly monitor peripheral locations without initiating a saccade. Additionally, in the first instance the duration of the time window reflects participants RT in response to the reversal in bomb direction. However, by degrees participants become aware that they can improve their RT by paying close attention to the temporal duration disparity between the distractor bombs and the penultimate bomb. Upon noticing this temporal disparity they must not make a saccade until the target bomb appears to be successful in the task. When they begin to pre-empt the arrival of the target bomb, as reflected in faster RT’s, the temporal disparity between the distractors is reduced.

161

Figure 33. The Delay Saccade Task temporal sequence: all distractor bombs appear for 500 ms except the last distractor which appears for 650 ms, thus providing a cue for the imminent change in bomb movement direction, the target bomb presented for the target duration. A saccade before the target duration or failure to make a saccade to the target location during the target duration results in failure.

9.4.2.6 Fixation task

Unlike the other tasks this was a single trial task, that is, it was not delivered in a block of 45 trials. Instead it was placed at the end of a block containing a different trial type. In this way it served as an “end of level boss”, a common concept in

162

computer games. The length of a trial for the fixation task was also considerably longer than the length of other trial types.

A fixation trial began with a short video sequence in which a larger bomb falls to the centre of the screen and breaks into six bomb segments. These six segments move in spate direction to the edge of the screen. At the centre of the screen a diamond appears. Participants must maintain their focus at the diamond at the centre of the screen. The diamond disperses their laser beam to the six bomb segments to destroy them all simultaneously after a period (see figure 34).

Participants must fixate at the centre of the screen for 30 seconds in total to succeed. While participants maintain a central focus distractors appear across the screen attempting to draw their focus away from the centre. The distractors appear at various locations and vibrate or fly across the screen. If the participants spend 5 seconds in total fixating away from the centre of the screen they set the bomb off and fail the trial.

163

The difficulty of the task is modified by altering the amount of distracters that appear. A second difficulty parameter is altering the total fixation time required to destroy the bomb, however this was not modified during the training. A potential weakness in the programming of this task is that when a participant looks at a distractor or moves in any direction away from the central fixation, all the distractors disappear; while this does serve to draw their attention immediately to their failure to maintain a central fixation, it may be of greater utility to allow them to notice this error themselves.

9.4.2.7 Additional Parameters, Tasks, and Training