PSY/BIO 226: Comparative Animal Behavior
(*See also this link for information on the difference between functional vs. descriptive definitions of behavior)
I. Ad Libitum ("at liberty") sampling: Also called "casual sampling" or "casual observation," "reconnaisance observation"
In this sampling technique, the observer takes free-form notes on what is happening. This technique by definition is not systematic or quantitative, and is most often used to get ideas and to begin to become familiar with an animal.
II. Systematic (quantitative) sampling:
There are two ways in which systematic sampling techniques can be described.
A. By What Is Being Sampled
One of these ways is by the sampling rule that is used by the observer. Is s/he concentrating her/his observations on only one individual, or on a group of individuals? Is the focus of the observation (the "sample") singular, or a collection of individuals or behaviors?
1. Focal Sampling: is the name given to systematic observation techniques in which the observer concentrates on just one individual
2. Group or Behavior Sampling: is the name given to systematic observation techniques in which the observer includes the entire group in his/her observations, or all of the occurrences (regardless of who performs them) of a behavior or suite of behaviors
B. By Time
1. Continuous sampling: in these systematic observation techniques, behavior is recorded continously over time
a. All Occurrences: as implied. All occurrences of a behavior are recorded as they occur. This technique is best used when your ethogram (and group of animals) is pretty small. Otherwise, it can get pretty hard to keep track of all that is going on.
b. Sequence sampling: as implied. All of the behaviors in a sequence of behaviors are recorded, in the order in which they occur, each time that they occur.
2. Discontinuous sampling: in these systematic observation techniques, behavior is recorded discontinously over time. Such recording techniques are better used for behaviors that are states (a behavior an animal exhibits for a period of time--such as walking, sleeping, foraging, etc.) rather than events (behaviors that are exhibited only occassionally and not for an extended period of time--such as fighting, scratching, biting, etc.)
a. Instantaneous ("on the beep") sampling: the behavior of a group or individual is recorded at set time internvals, and what is recorded is what the animal is doing at the moment that the time interval expires.
b. Scan sampling: This term is sometimes used synonymously with instantaneous sampling. In scan sampling, a group or individual is scanned at set time intervals, and whatever the group or individual is doing at the moment of the scan is recorded.
c. One-Zero sampling: In this technique, what is recorded is whether or not a behavior occurred within a set time interval of observation. If the behavior occurred, it gets a score of 1. If it did not occur, it gets a score of 0. Hence the name.
III. Other Recording Techniques:
A. Trace Methods: Using this method, the observer does not actually observe behavior as it occurs, but rather, infers that behavior occurred by looking at the "traces" that the behavior left behind.
1. Trace Method of Erosion: as implied. This method involves making inferences about behavior by looking at what the behavior has eroded, or worn away. For example, one can make inferences about the amount of traffic a particular animal trail gets by measuring the depth and width of the trail (i.e., how much the behavior of traveling on that trail has eroded the ground). Similarly, I have had students infer what swing on a swingset was most popular by measuring the degree of erosion under each swing.
2. Trace Method of Accretion: as implied. This method involves making inferences about behavior by looking at what the behavior left behind. For example, in my Master's thesis observations of wild boar in California, I used the trace method of accretion to determine the popularity of given "rubbing trees" and the relative traffic each tree received by measuring the amount of mud left on each tree (the boars would wallow in mud to cool off, then scratch themselves clean on specific trees, leaving a dense coating of mud on those used most often). Similarly, other social scientists make inferences about attitudes by using the trace method of accretion--this time looking at what those attitudes leave behind in the form of graffiti.
B. Behavioral Mapping: In this technique, behavior is "mapped" to space. Environmental psychologists, animal behaviorists, and others use this technique to determine how animals (both human and nonhuman) use space, and how the environment influences behavior
1. Place-centered behavioral mapping: In this technique, the observer maps an area of interest, and then records what individuals do in different areas of the map. Using this technique, for example, researchers can determine where to put park benches (by looking at where people spend time standing and chatting with one another in a local park), or where to put nesting material for a zoo animal (by noting where the animal spends most of its resting time).
2. Person- or Animal-focused behavioral mapping: In this technique, the observer is interested in where a particular animal or person goes, and what s/he does when s/he gets there. Such a technique might again make use of maps, but uses a focal sampling technique. What is recorded is where the individual goes at different times of day, and what he or she does once there.
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