Abstract
Rats will be observed on a time-sampled schedule for fifty minutes. The inter-observer reliability will be assessed with a per cent agreement score, and the transition matrix of behaviours will be computed from the observations.
Introduction
Our first study is a modest one. Basically, we will describe our rats' behaviors over a fifty-minute period, using a time-based sampling procedure. Of interest is the way the rat distributes its activities and the way different behaviors relate to each other.
Although the observation procedure is simple, the method of analysis can be quite complex. There is, first of all, the issue of reliability of measurement. Are the observations consistent against some operational criterion? Typically, this is assessed by looking at whether two observers agree with respect to a behavioural observation. A simple way to measure agreement is to look at the percentage of observations in which two observers classify the behaviour in the same way.
Another aspect of the data is the time budget. That is, what percentage of the time is spent in different activities? This measure is particularly easy to compute when behavioural observations have been classified into mutually exclusive categories. A more informative picture of the temporal aspects of a behaviour, however, is to look at the distribution of different durations of "bouts" of the behavviour. For example, given that the rat shows behaviour x, how many times does that behaviour last io seconds? How many times does the behaviour last 20 seconds? Or 30 seconds? Such an analysis allows one to determine the lifetime of a given behavioural "bout."
At the most complex level, one could ask how different behaviours relate to each other. For example, given that the rat is engaged in a bout of behaviour x, how likely is it that the rat will next do behaviour y? One way to answer this question is to develop a transition matrix,in which we examine behaviours at one time and then relate them to the behaviour in the next time interval. This type of analysis can sometimes be used to develop a "Markov chain" that describes behaviour over successive episodes. Other, more complicated, measures are also possible, including the possibility of a "grammatical" description of behaviour.
Procedure
Subjects. Our Sprague-Dawley rats will serve as the subjects.
Aparatus. We will use clear plastic observation chambers and a clock that can give 10 second intervals.
Procedure. Each rat will be observed for 50 minutes. During each 10 second interval, each member of the team is to record, independently, the dominant behaviour of that interval. The behaviours are:
Grooming. Washing or brushing movements directed towards the rat's fur.
High sniff. Standing with nose above medial plane, with pronounced nostril movement.
Low sniff. Standing with nose below medial plane, again with pronounced nostril movement.
Walking. Movement on all fours.
Freezing. Complete absence of movement except moderate respiration.
Gnawing. Chewing some part of the chamber.
Other. Not in any of the above categories.
You and your partner should spend some time discussing these categories, and agreeing on their definition. When you are ready, start the time, and record on a sheet of paper with 300 spaces (a ruled sheet with different columns will suffice) the behaviour exhibited during successive to-second intervals. Make sure you and your partner stay synchronized.
Results
I would like to see two apsects of your data. First, I would like a per cent agreement score, consisting of the percentage of observations on which you and your partner agree. Second, using one of your score sheets, I would like a transition matrix. The form of this matrix will be discussed in class before the start of the study.
Along with your notes, provide a short reflection on the behaviour of a rat in one of these chambers.
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