# Free interval based on a Trial Control event

Background

This topic contains details about defining a Free interval. For the main procedure, see Free interval.

To specify the Trial Control event

In the Free Interval window, under Start criterion or Stop criterion, choose Trial Control and select the following:

1.In the Start at / Stop at field, enter the time of the start (or stop) of the interval relative to the Trial Control event specified in the next steps.

example 1 To start an interval 1 s before a Trial Control condition becomes true, next to Start at enter 0:00:01:000 before event.

example 2 To stop an interval 10 s after the Trial Control action “Drop pellet”, next to Stop at enter 0:00:10:000 after event.

2.From the Occurrence list, select which occurrence should mark the start of the interval (1st to 9th).

Select 1st if you want to define an interval from the first time that a trial control event occurs. Select 2nd, etc. when the trial control event occurs repeatedly, for example in sub-rules.

3.From the Element list, select the trial control category (condition, action, sub-rule, etc.).

4.From the Event list, select the event. The options differ depending on the Element chosen.

▪For actions, sub-rules: becomes active/inactive.

▪For conditions: becomes active/inactive, and becomes true/false.

▪For sub-rule references: becomes active/inactive, and makes sub-rule active/inactive.

Return to To specify a Free interval

Notes

▪A Free interval can only start at the time that, or before (not after) a Trial Control event occurs. Similarly, a Free interval can only end at the time that, or after (not before) a Trial Control event occurs.

See also

▪For information on the meaning of active/inactive, false/true, see How the trial control instructions are executed.

▪For information on sub-rules and analysis of trial control data, see the EthoVision XT 19 - Trial and Hardware Control - Reference Manual.

Difference between Free Intervals based on Trial Control and Nesting over a Trial Control state

With Free intervals you can select the same track segments that you can define with Nesting over a Trial Control state in the Data profile. The main differences are that:

▪With a Free interval, you can also specify the number of occurrences of an event in the Interval start criterion. For example, define an interval that starts when an action is carried out the 3rd time. With Trial Control state that is not possible. There, you can only specify the number of occurrences in the Interval stop criterion.

▪With a Free interval, you can combine Trial Control events with other criteria (time, dependent variable values, hardware log values). For example, define an interval that goes from the time a light switches on, to 1 minute after that time.