# Method: Three-Chamber Sociability Index Calculator (method version 1.0.0)

## Calculation

For each animal, from the time spent in each chamber (and, where scored, in the interaction zone around each wire cup):

1. **Sociability index** SI = (stranger − empty) / (stranger + empty), from the chamber times; **SI (zone)** uses the interaction-zone times. Positive values mean more time with the stranger.
2. **Social novelty index** SNI = (novel − familiar) / (novel + familiar), from the chamber times; **SNI (zone)** uses the zone times.
3. **Preference scores** = target / (target + other) × 100, with the stranger (sociability) or the novel mouse (social novelty) as the target.
4. **Habituation side preference.** With L and R the times in the left and right side chambers of the empty apparatus, the left share is L / (L + R). The animal is flagged when the left share is above 60% or below 40%. Center time does not enter.
5. **Group statistics** per group: mean, standard deviation (n − 1 denominator) and SEM = SD / √n of each index, over the animals whose index is computable.

## Conventions

- Times are in seconds.
- An index or preference score whose two compared times are both 0 is not computable. The table shows "—", the CSV leaves it blank, and the animal is left out of that index's group statistics. A group in which no animal has a value for an index shows "—" for it.
- Left and right habituation percentages are shares of the side-chamber time. An animal with no side-chamber time is not flagged.
- The per-animal chamber bars show each chamber's share of the whole sociability phase, center included.

## Worked examples

Three cases in `cases.json`: a sociability index worked by hand, a habituation side preference that only the side-chamber rule detects, and an animal with no time in either compared chamber (edge case).

## References

- Kaidanovich-Beilin O, Lipina T, Vukobradovic I, Roder J, Woodgett JR. Assessment of social interaction behaviors. Journal of Visualized Experiments. 2011;(48):2473. https://doi.org/10.3791/2473

The reference describes the test (sociability and social novelty sessions, alternating the stranger's side). The indices, preference scores and the 60/40 side-preference rule are this tool's conventions; in the reference protocol the side chambers are closed off during habituation.

## Changes from the page before this record

- The habituation side-preference flag divided the left and right times by the whole session, center included, and flagged a gap of more than 20 points. Most center time hid real side preferences: left 200 s, center 300 s, right 100 s splits the sides 67/33 but was not flagged. The flag now uses the side chambers only, and the displayed left and right percentages are shares of side-chamber time.
- An index or preference score with no time in either compared chamber or zone was 0, which entered the group mean. It is now not computable and left out.
- Values for animals with time in the compared chambers are unchanged.