# Make and break group

Definition

A discrete (point event) variable that is scored when the focal subject joins or leaves a group of conspecifics. Because it is a point event variable, it has no duration.

▪Make group of size n (2 to 4). The subject joins a group of n-1 subjects to form a group of n subjects in contact with each other.

▪Break group of size n (2 to 4). The subject leaves a group of n subjects. The group is now of size n-1, or does not exist anymore in the case of n=2.

Calculation

EthoVision XT detect the make/break events based on the state of type Group.

▪If the subject is not in contact with any subject one video frame before the start of the event Group, a Make group event is scored.

▪If the subject is not in contact with any subject one video frame after the end of the event Group, a Break group event is scored.

note In EthoVision XT, a point event is an event with no duration. In contrast, state events have a duration.

How to specify Make and break group

1.Open an Analysis profile and in the Dependent Variables panel, under Live Mouse Tracker, click the Add button next to Make and break group.

2.Specify the Group size. This is the final size when making a group, or the initial size when leaving a group. For example, enter 3 if you want to have the instances when a subject joined other subject to form a group of three subjects, or left a group of three, so the group became of two subjects.

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

Applications

In a study of mouse model of ASD, Shank2 mutant mice observed in a social context displayed increased frequency of completing or breaking a group of three or four mice (de Chaumont et al. 2019. Nat. Biomed. Eng. 3: 930-942.

Note

While Group is a state event that aims at quantifying the time that a subject was part of a group, Make and break group is a point event variable, that is, it tells you exactly when the subject joined or left a group.

See also

▪Dependent variables for Live Mouse Tracker