Stretch attend posture

Definition

A discrete (state event) variable that is scored when the subject slows down and stretches its body forward. The subject’s apparent body length (measured from the top view) increases and its height (measured with the depth camera) decreases.

Calculation

1.EthoVision XT calculates the average and the standard deviation (SD) of the body length, measured as the distance between the nose-point and the tail-base point, throughout the entire track.

2.EthoVision XT calculates the median body height, where body height is measured using the z-coordinate of the subject’s center point.

3.Stretch attend posture is scored when the following occur simultaneously:

▪The current body length is equal to or greater than the average + 1 SD of the body length.

▪The current body height is smaller than the median body height.

▪The current speed of the subject is lower than 5 pixels per video frame (at 30 fps, this is about 26 cm/s).

How to specify Stretch attend posture

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

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

Note

Stretch attend posture is not detected if the nose-point or the tail-based point are not found at that time. The software needs both points to estimate the body length.