# Follow

Definition

A discrete (state event) variable that is scored when the focal subject walks directly in the path of another subject.

Calculation

Follow along path is scored when the following conditions are met:

▪Both subjects move at a speed higher than 5 pixels per frame.

▪The two subjects are not in contact with any other subject.

▪The angle between their direction vectors is smaller than 45°.

▪The focal subject’s center point lies within a rectangular area drawn based on the position of the followed subject. This is checked beginning from the current video frame time to the 15th frame before the current one. So the software checks that the focal subject enters the path up to 0.5 s after the followed subject has been there.

▪The distance between the two subjects’ center points is smaller than two mean body lengths. This mean body length is calculated using all values of distance nose-tail base of the followed (i.e., non focal) subject within the track.

How to specify Follow

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

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

Note

Follow looks similar to a train of two mice. However it depends on the definition of the train.

If subject A is following closely subject B, this is scored as A Follows B but also as a Train for subject A, when the distance between A and B is shorter than the threshold set in the Train settings, and when the train is defined as in the cases below:

▪A > B.

▪Actor > B.

▪Actor > Any.

Note that:

▪Follow is scored for the subject that follows another one. If subject A follows subject B, Follow is scored for subject A, not B.

▪Train is scored for all the subject involved in the train definition. So when subject A follows subject B, an instance of Train defined as A > B is scored for subject A and for subject B.

See also

▪Dependent variables for Live Mouse Tracker