# Distance between subjects

Definition

The distance between a body point of a subject and a body point of another subject.

Distance is calculated for each Subject (Actor) relative to other subjects (Receivers).

Calculation

Formula:

Where DSk is the distance between Actor and Receiver at sample k, Xa,k and Ya,k the X,Y coordinates of the selected body point of the Actor at sample k, and Xr,k and Yr,k the X,Y coordinates of the selected body point of the Receiver at sample k.

How to specify Distance between subjects

1.Click the Add button next to Distance between subjects.

2.Click the Body points tab and select the body points of the focal subject (Actor) you want to use to calculate distance.

3.Click the Receivers tab. Here, you specify the other subjects (Receivers).

▪Under Select, choose the subjects you want to calculate the distance from.

▪Under Body points, select the body points of the subjects selected above.

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

Notes

Distance is calculated for each combination of Actor's body points and Receiver's body points. Each row of the result table shows the results for an Actor. For example: The row heading shows Subject 1. The column heading Nose point / Subject 2 / Center point. This can be read as ‘the cell contains the distance between the nose point of Subject 1 and the center point of Subject 2’.

Applications

This parameter forms the basis for the Proximity dependent variable used in studies of social or aggressive behavior. In zebrafish, shoaling behavior is analyzed with Distance between subjects; see Green et al. (2012) J. Neurosc. Methods, 210, 266– 271.
Social Contact
A discrete (state event) variable that is scored when the subject (actor) is near a conspecific (receiver). The actor's nose point is within a specified distance from the receiver's body, and the actor's center-nose vector is oriented toward the receiver's body points by less than the specified angle.

Parameters:

▪Orientation-independent contact distance — Within this distance, contact is scored regardless of the actor's orientation.

▪Maximum distance — Beyond the orientation-independent distance and up to this value, contact is only scored when the orientation criterion is met.

▪Maximum orientation angle — The maximum allowed angle between the actor's center-nose vector and the direction toward the receiver's body points.

Approach

A discrete (state event) variable that is scored when the subject (actor) moves toward a conspecific (receiver) within the specified distance. The angle between the actor's center-nose vector and the receiver's center point is less than specified. The receiver moves at a velocity lower than the specified value.

Parameters:

▪Minimum distance — The minimum distance between actor and receiver for the event to be scored.

▪Maximum distance — The maximum distance between actor and receiver for the event to be scored.

▪Maximum orientation angle — The maximum allowed angle between the actor's center-nose vector and the direction toward the receiver.

▪Maximum velocity of receiver (Advanced) — The receiver must move slower than this value. This distinguishes approach from mutual movement.