# Trial Control event

Definition

A point event, with no duration, defined by an element of Trial and Hardware Control (condition, action, rule/sub-rule and reference).

A Trial Control event has no duration. For Trial Control events you can only calculate frequency and latency of first or last occurrence.

How to specify Trial Control event

1.Click the Add button next to Trial Control event.

2.From the Element list select the Trial and Hardware Control element to be analyzed. For example, if you want to analyze the hardware-base action ‘Drop pellet’ select Action: Drop pellet.

3.From the Event list, select the state of the element. The options available depend on what you have chosen as Element.

4.Complete the procedure to add the variable. See Calculate statistics: procedure.

Notes

▪Statistics of Cumulative duration and Latency can only be a multiple of the sample interval (=1/sample rate). For example, when you define a condition ‘Subject in zone A for >= 3 s’, this condition is met when the time elapsed from its activation exceeds 3 s. If the sample rate is 12.5 frames/s (thus the sample interval is 1/12.5= 0.08 s), the condition is met at the first multiple of 0.08 greater than 3 s, that is 3.04 s. This affects data analysis, for example the latency of the event ‘Condition becomes true’ is 3.04 s

▪For Trial Control events based on Conditions, the sample time at which a Trial Control event is scored also depends on the statistic used in the condition:

If you use Current to define the condition (for example: “when Current In zone= true”), the Trial Control event is scored at the expected sample time. For example, when the animal enters the zone (and thus Current= true for that sample). See also A in the figure in Trial Control state, where the start of the Trial Control state is like a Trial Control event.

If you use any other statistic to define the condition (for example, “when Frequency of In zone >= 1), consider the following scenarios:

▪- When the condition becomes true after the condition box is activated, the Trial Control event is scored at the expected sample time. See How the trial control instructions are executed for an explanation of the terms true and active.

▪- When the condition is already true when the condition box is activated (for example, a condition “Frequency of In zone =1” is activated when the animal is already in the zone), such statistic is only evaluated at the next sample (or in the second next sample, in the case of Heading). In that case, the Trial Control event is scored one sample (or two) later than expected from the condition (see B in the figure in Trial Control state). However, for the consecutive frequencies of In zone =2, 3, etc, the condition is already active by definition; therefore the Trial Control event is scored at the expected time, when the condition becomes true.

See also

▪The EthoVision XT 19 - Trial and Hardware Control - Reference Manual. To open this manual, choose Apps > Noldus > EthoVision XT 19 Other Documentation.

Application

You can use Trial control event to test whether trial control works as expected. For example, visualize the Trial control event ‘condition true’ and plot it together with the video to check that the condition is met at the correct time. You can also define a Trial control event to calculate the number of occurrences of specific actions like dropping a food pellet in a learning experiment.