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For all the examples below, define the interval first, then choose Analyze > Results to calculate the statistics or visualize the results.

Tip: If you want to define a free interval to further analyze the events within that interval, choose Nest over a Free Interval in the Data profile.

Examples

• Example 1: From the track start to when the subject is in a zone for a specific time
• Example 2: From the start of a conditioning routine to when 10 rewards are given to the subject
• Example 3: Split a track in segments of a specific path length
• Example 4: Detect bouts of a behavior
• Example 5: From the track start to when external (physiological) data reach a specific value
• Example 6: Filter the instances of a behavior longer than a certain time

Example 1: From the Track Start to When the Subject Is in a Zone for a Specific Time

Aim

This free interval can be used, for example:

• Exploratory behavior. Calculate the time that the subject takes to explore the novel object for at least 30 s (Cumulative duration).
• Learning. Calculate the time that the animal takes to stay in a zone for 30 s uninterrupted (Current duration).

Solution

Define a Free interval with:

• Start criterion: Track start
• Stop criterion: Dependent variable In zone. The Statistic depends on the type of question you want to answer.

In the Novel object test, you want to stop the interval when the subject has explored the object for a total of 30 s. Choose Cumulative duration.

In the learning example, you want to stop the interval when the subject enters a zone and stays for 30 s without exiting. Choose Current duration.

Example 2: From the Start of a Conditioning Routine to When 10 Rewards Are Given to the Subject

Aim

In a conditioning experiment, the subject has to stay in a specific zone to obtain a food pellet. The action-reward sequence is repeated a number of times in a subrule. The researcher wants to know how long it took the subject to get 10 rewards.

Solution

Create a Free interval with:

• Start criterion: Trial Control. Element: Subrule. Event: becomes active.
• Stop criterion: Hardware. Device type: Pellet dispenser. Select signal: Number of drops >=10. The option Cumulative is selected.

Example 3: Split a Track in Segments of a Specific Path Length

Aim

Suppose you want to split your tracks in segments of a specific distance moved by the subject, for example 1 m, and you want to calculate the duration of each segment.

Solution

Create a Free interval with:

• Start criterion: Dependent variable Distance Moved. Statistic: Current ≥ 0 cm.
• Stop criterion: Dependent variable Distance Moved. Statistic: Total ≥ 100 cm.

To calculate the duration of individual instances, select Calculate statistics per interval and enter a number that exceeds the maximum number of intervals per track.

Plot 1: Per-sample distance moved. Plot 2: Free interval that runs from Current Distance Moved ≥ 0 to Total Distance Moved ≥ 100 cm. Note that the faster the animal (i.e. the longer the per-sample distance moved), the shorter the resulting interval.

Example 4: Detect Bouts of a Behavior

Aim

Calculate the number and duration of bouts of a behavior, for example Movement or Activity. The single instances of Movement being part of a bout may be separated by up to time tmax. In the example below, instances 1 to 5 are grouped in a bout.

Solution

Create a Free interval with:

• Start criterion: Dependent variable Movement with state Moving. Statistic: Current.
• Stop criterion: Dependent variable Movement with state Not moving. Statistic: Current Duration ≥ 5 s (tmax). This ensures that the interval ends when the animal has not moved for five seconds without interruption.

In the Trial Statistics tab of the same window, select Mean if you want to know the average duration of a bout.

Notes

• Because each free interval also includes tmax, you have to subtract that time to obtain the true average duration.
• If the event which specifies the end of a bout (in this example, Not moving for at least 5 seconds) is never found, the result for that trial is that there is no bout at all. The result is one long bout if you de-select the option Ignore last interval if incomplete.
• For the same reason described above, if the Stop criterion is not met, the last bout of a trial is not detected — for example, when the time between the start of Not moving and the end of the trial is less than tmax. You can have the last bout detected by selecting the option Ignore last interval if incomplete, but the duration of this bout will be truncated.

Example 5: From the Track Start to When External (Physiological) Data Reach a Specific Value

Aim

To calculate the time that it takes for a physiological variable (e.g. heart rate) to reach a specific value.

Prerequisite

The physiological variable has been imported in the trial. See External Data.

Solution

Create a Free interval with:

• Start criterion: Track start
• Stop criterion: Dependent variable Heart rate. The Statistic chosen is Current. If necessary, click Settings and choose how to re-sample the variable from the original signal. See External data (resampled).

The result is shown in the first plot, together with the plot of Heart rate. Choose Analysis > Results > Statistics and Charts to obtain the length of the free interval.

Tip: If you want to analyze the time between two values of external data — for example, from Heart rate = 300 to Heart rate = 400 — choose External data (state) in the Analysis profile instead of Free interval.

Source: EthoVision XT 19 Help, Noldus Information Technology