# Using Trial Control variables

Aim

Trial Control variables help you keeping track of events that occur during the trial. An example of a Trial Control variable is a counter.

To define a Trial Control variable

1.Open or create new Trial Control Settings.

2.In the Components pane, under Conditions or Actions click the button next to Trial Control variable.

3.Next, click the Variables button. The Trial Control Variables window lists the variables currently in the experiment (also those defined in other Trial Control Settings). To add a new variable, click Add variable.

4.A new row is appended to the table. Under Name, type in the name you want to give to the variable. Under Initial Value, enter the value of this variable at the start of the trial (default: 0).

5.Click OK. In the TC-variable action/condition window, define the action or condition you require. Click Cancel if you do not want to create a condition or action based on that variable at that point.

Notes

▪To delete a variable, click the variable name in the Trial Control Variables window and click the Delete variable button.

▪To rename a variable, click the variable name in the Trial Control Variables window and edit this name.

▪The default name of a new trial control variable is VarN, where N is a progressive number.

▪The variable name cannot contain blank spaces.

To define an Action on a Trial Control variable

1.In the Components pane, under Actions click the button next to Trial Control variable. If you do not see this action, under Actions click the More button.

2.If the Add an action window appears, it means that there is at least one action of the same type in your experiment. You are asked to choose between creating a new action, or re-use an existing one. See Re-use trial control elements .

3.In the TC-Variable Action window, next to Action Name, enter the name of the action (for example, Increment Counter) or accept the default name.

4.Under Action to perform, select the variable from the list. You can also create the variable by clicking Variables if you have not yet done so.

5.Next to the = symbol, do one of the following:

▪To assign the same value of another variable (for example A = B), select the other variable (B) from the second list.

▪To enter a formula, click the double-arrow button.

Select the operator from the list and specify the formula in the second and third lists. For example, A= A + 1.

▪To assign a random value, select Random from the second list, and select the Minimum and Maximum limits (only integer values, 0 up to 999) for the random value.

For the Permutation option, see below.

6.Click OK. Insert the resulting Action box in the Trial Control rule.

Notes

▪If your setup includes multiple arenas, each arena receives an instance of the variable. Thus, a variable can have different values in different arenas.

▪You cannot combine Random with a formula (for example, to compute A= Random+1). The equivalent solution is the following: define first an action B= Random, and then one more action A= B+1. Place the two resulting Action boxes in sequence.

▪For a random variable, select the Permutation option to generate a random value that is unique in the sequence of all values in the specified range. For example, if the Minimum is 1 and the Maximum is 5, any value will be generated only after all the other possible values have been generated in previous repeats of the action. That is, a new value 1 can only occur after that all the other possible numbers are generated during previous repeats of the action: 3, 2, 4, 1, 5, 1. Use the Permutation option to create sequences of unique numbers, for example to activate routines in a “pseudo-random” order but without the repetitions that would occur if you generate fully random numbers (e.g. 2, 4, 1, 1, 5).

See also

▪The EthoVision XT - Trial and Hardware Control - Reference Manual. See Manuals