Archive for November 20, 2008

Starting Phase 2 — Hoarding Together

Over the last few days, we have been implementing phase 2 in which we put both rats in the tank together, separated by the wire mesh barrier. For this stage, each rat will remain on her particular side (which we marked with tape) and each rat’s tissue box and washcloth are placed next to each other on each side of the barrier. We run each trial the same way we did in phase 1, except that both rats are run at the same time! To refresh your memory, this is what the apparatus looks like:


And this is what it actually looks like (including both rats):


We are hoping to see either an increase or decrease in hoarding when they are together in comparison to the trials in which they were apart. We have reasoning to believe that a change could occur in either direction.

1) Explanation for why they may hoard more when apart than together:

-When together, they are distracted by the other rat’s presence and simply are too distracted to hoard.

-When apart they are more comfortable (less threatened by the possibility of another rat stealing their food) and therefore hoard more.

2) Explanation for why they may hoard more when together than apart:

-Social facilitation theory–Perhaps when in the presence of one another, the rats are aroused into performing better on the simple task of hoarding.

-Fear that if they do not hoard many pellets, the other rat may steal from their food source or even their hoard.

-Competition for resources

After three trials of running the rats together, Louise has hoarded an average of 29 pellets and eaten an average of 2.9 grams. Penelope has hoarded an average of 46.3 pellets and eaten an average of 3.9 grams.

We have noticed a number of interesting things:

-The rats seem to be hoarding faster than in “alone” trails but not necessarily significantly more pellets.

-When they see the other rat running toward her food pile, each rat (Penelope especially) tends to follow them to the “food end” of the tank, and then begin hoarding as well.

-The hoarding tends to occur in spurts, with distracted behaviors such as sniffing each other through the screen, jumping up on their boxes, and running around the cage in between.

-Louise likes to jump out of the tank! (This very suddenly started happening and we’re working on it!)

We have included a video that further explains what we have observed.

Here are some graphs that show what is going on with our experiment.


This graph shows the number of pellets hoarded by both Louise and Penelope during the first three trials together.


This graph shows Louise’s hoarding while alone compared to her hoarding with Penelope in the box.


This graph shows Penelope’s hoarding while alone compared to her hoarding with Louise in the box.

November 20, 2008 at 1:39 am Leave a comment


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