About the task
Purpose: to train the subject to touch stimuli.
A trial begins and marker sound 1 is played. Object(s) are presented on the screen. If the subject responds correctly within a criterion time, reward it. If the subject responds incorrectly or fails to respond, punish it.
| • | Level 1: correct response is touching any object |
| • | Level 2: correct response is touching an object that is designated Correct |
| • | Level 3 (sequential touching): trials have two phases. In phase 1, a single object is presented in the centre of the screen. If the subject touches it, we proceed to phase 2; otherwise, we punish. In phase 2, we play marker sound 2, and present three other objects; if the subject touches any one, it's rewarded (otherwise, punished). |
Configuring the task
| • | Maximum number of trials. When the subject has performed this number of trials, the task ends. (You may specify 0 for no limit, though you must specify a limit on the number of trials, the time, or both.) |
| • | Maximum time. When this time elapses, the task is terminated as soon as the current trial has finished. (You may specify 0 for no limit, though you must specify a limit on the number of trials, the time, or both.) |
| • | Response criterion time. If the subject fails to respond to a stimulus within this time, an omission is scored. |
| • | Starting level. The task will start at this level. |
| • | Increase level during task. If enabled, the level will increase as the task goes on. You can either increase the level after a fixed number of trials, or when the subject reaches a criterion of a certain number of "correct" trials within the last 20 trials. Fill in this number (either the number of trials, or the number to get right out of 20) in the box labelled X. |
| • | Time between trials. Specify a minimum and a maximum intertrial time (they may be the same). The actual time is chosen with a rectangular probability distribution within these values. |
| • | Time between phase 1 and 2. Only applies to level 3 (sequential touching). This sets the time between the subject responding to the phase 1 stimulus and the stimuli for phase 2 being presented. |
| • | The set of objects to use is shown in the list at the bottom right. You may add objects from the library, remove them from the list, and toggle their status as being Correct or Incorrect (for Level 2, see above). You may add objects more than once. Objects are selected with equal probability from the list you see (so if you enter an object twice, you double its chance of being used; you can also have two copies of the same object where one is designated Correct and one is Incorrect, should you choose). |
Options for reward and punishment are set in the General Parameters section; visual objects are defined in the Visual Object Library.
More on displaying objects
The task works with an internal scaling system based on a display that is 1000 units (pixels) wide and 750 high. Each object should fit into a rectangle that is 267 (w) x 200 (h).
Imagine that the screen is divided into nine. (See this diagram ("Size and coordinates").) When one stimulus is displayed, it is shown in the centre; when three are shown, they are position at the top centre (stimulus 1), bottom left (stimulus 2), and bottom right (stimulus 3).
Screenshot from the task
Touch my monkey. TOUCH IT!
