# Body contact

Definition

A discrete (state event) variable with two possible states, In contact and Not in contact, based on whether the subject’s body contour is in contact with the body contour of any of the other subjects.

note Body contact is not available or does not give results if:

▪The tracks were recorded in EthoVision XT 11 or earlier.

▪Your experiment is set to:

▪Color marker tracking.

▪Live Mouse Tracker - But see Raw Live Mouse Tracker data

▪Center-point, nose-point and tail-base detection, with two subjects per arena tracked with Deep learning.

How to specify Body contact

1.Click the Add button next to Body contact.

2.In the Body contact tab, select the state you want to analyze.

For example, select Body Contact if you want to know how often or how long the subjects were in contact during the test.

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

Notes

▪An animal’s contour is determined by computer vision, which is unlike human vision. This is exemplified when dark animals are tracked: often their shadow on the background will be considered part of the animal. Thus, the detected contour is regularly a bit bigger than the human eye would observe.

▪Body contact is not subject-specific. That is, you cannot isolate instances of contact for a specific combination of subjects (for example, Subject 1 in contact with Subject 3). Instead, use Proximity and specify the two subjects.

▪Body contact is based on the subject’s contour, while Proximity is based on the distance between subject’s body points. For example, two subjects next to each other may be in proximity, but not in body contact.

▪Body contact is affected by the track smoothing methods The Minimal Distance Moved smoothing method and The Maximum Distance Moved smoothing method. When you apply one of those methods, Body contact is recalculated and may be slightly different with respect to when the method is not applied. The difference is usually limited to one or a few samples.

Applications

Body contact can be used in any social interaction tests:

▪To quantify the level of interaction between subjects. Add Body contact in the Analysis profile (see above).

▪To exclude instances of body contact when these result in unreliable tracking. In this case, instead of adding Body contact in the Analysis profile, in the Data profile choose Nesting over Body contact and select Not in contact.

Below: Integrated Visualization of Body contact in a 2-subjects test.

tip In Integrated Visualization, the body contour is not visible. To view the body contour, open Acquisition, click the Show Hide button, choose Detection Features and select Body contour.