Knowledge Base

Problem

Users observe false-positive zone entries or exits, particularly near zone borders, and attempt to find a 'zone is entered when' threshold setting that does not appear in their version of EthoVision.

Details

In EthoVision XT, zone entry is a Boolean measure: a body point is either inside the zone boundary or not. There is no configurable entry-percentage threshold at the arena level. False positives caused by body-point tracking jitter near zone edges cannot be corrected by arena settings alone. A limited post-acquisition option exists: the zone exit threshold for the 'In Zone' parameter can be adjusted in the Analysis settings. Reducing false positives primarily requires improving detection settings. Reported in EthoVision XT version 12 and likely affects other versions.

Solution

1. Understand that zone entry in EthoVision is binary – the selected body point is either inside or outside the zone; there is no entry-percentage option in Arena Settings.
2. To reduce false positives caused by body-point jitter, review and improve the Detection Settings (e.g., smoothing, body-point selection, or tracking parameters) rather than arena settings.
3. For post-acquisition adjustment, go to Analysis > Parameters > In Zone, and use the zone exit threshold option to require the animal to move a minimum distance outside the zone before an exit is registered. This can reduce spurious entry/exit events.
4. Consider selecting a more stable body point (e.g., center point rather than nose point) if nose-point jitter near zone borders is the main source of false positives.
5. If tracking quality is poor, consider retracking the trials with adjusted detection settings.