Knowledge Base

Problem

Users want to analyze tracking data only for periods when the animal has been continuously inside a specific zone for at least a defined minimum duration (e.g., count a visit only after the animal has been in the zone for 2 seconds), and stop counting once the animal exits. The standard 'In Zone' nesting option does not support a duration threshold.

Details

The built-in 'In Zone' nesting option in EthoVision's Data Profile selects all track segments where the subject is within a zone, but it does not allow a minimum time-in-zone condition before the interval is counted. This is relevant for experiments requiring a sustained presence threshold (e.g., fish exploration zones, novel object interaction). The 'Free Interval' nesting option provides the necessary flexibility.

Solution

1. Open **Analysis > Data Profile** for your experiment.
2. Under **Nesting**, select **Free Interval** instead of 'In Zone'.
3. Define the interval **start condition**: set the start event as the subject entering the target zone AND having been in the zone for the required minimum duration (e.g., using a state variable that becomes true after the subject has been in the zone for the threshold time).
4. Define the interval **end condition**: set the end event as the subject exiting the target zone.
5. This configuration ensures that only visits meeting the minimum duration requirement are included in the analysis interval.
6. **Tip**: If you do not have a pre-defined state variable for time-in-zone duration, you can create one using a **Conditional Variable** in the Experiment Settings that becomes active after the subject has been continuously in the zone for the threshold duration. Use this variable as the start trigger for the Free Interval.
7. Verify the nesting by reviewing the interval markers in the Track Editor to confirm only qualifying visits are highlighted.
8. Run the analysis and export results as normal.