Physical Trace Measures

Trace measures are the physical remains of interaction. When investigating a crime, police operate under the assumption that "every contact leaves a trace" (1). At the crime scene and elsewhere, police seek traces of the criminal -- fingerprints, footprints, fiber from clothing, hair, cigarette butts, blood type, DNA, and whatever else might help solve the crime. Similarly, researchers use physical traces as indicators of behavior. There are two general types of trace measures: Accretion - a build-up of physical traces, and Erosion - the wearing away of material.

Litter

Litter is an accretion measure - something added. A researcher studied litter remaining on tables in a student lounge and a fast-food restaurant. Despite signs asking "Please bus your tables," some customers left things on the table rather than put them in recycling bins or trash receptacles. Males left more trash than did females, and littering was more frequent on tables that were far from receptacles.(2)

In another study of litter, a cultural anthropologist in New York City used discarded drug paraphernalia as a trace measure indicating illegal drug use. In neighborhoods where there was heavy drug trade, he found sidewalks strewn with variously-colored crack vial tops, intact or discarded syringes, and spent butane lighters. In the same way that archaeologists use bone fragments and pottery shards as signs of early settlement, this anthropologist used the crack vial tops and other materials to indicate a work site or use location for illegal drugs. He spent time in the neighborhood developing relationships with the participants in the drug trade in an attempt to understand their world. The trace measures gave him added confidence that he was studying the right people in the right locations.(3)

Graffiti

Graffiti is unauthorized writing and drawing on various surfaces -- walls, vehicles, subway cars, tunnels, bridges, etc. It is generally accretive, but in the case of scratching or etching, would be a form of erosion.

A systematic study of graffiti often involves an application of content analysis - see the Content Analysis module for more detail. The researcher selects areas for single or periodic sampling. Then a classification system is developed for recording the findings. More ....

Latrinalia is the technical name given to graffiti on public toilet walls. It tends to express attitudes and sentiments that are socially disapproved. American men's toilet walls reveal a preoccupation with sexual experience, excretion, ethnic hostility, and divergent political views.

Example: Coding categories for studying graffiti in college restrooms. The recording sheet should be accompanied by more detailed definitions of the categories, including examples to assist those doing the scoring.

Erosion or wear

Erosion or wear can reveal usage patterns. Researchers studying animal behavior in the field record trails, tracks, and scratch marks.

Deterioration of campus lawns and the footprints in the snow reveal informal pathways. Astute university administrators delay installing walkways until after trails have emerged.

Pathways can be used to assess the social relationship between people in different buildings. Footprints do not provide an infallible measure of contact, but may be a clue worth following.

In past years the floor tiles around the hatching chick exhibit at Chicago's Museum of Science and Industry were replaced every 6 weeks, while tiles in other parts of the museum lasted for years.(4) Tile wear can be a good index of the relative popularity of exhibits.

Animal behavior

At sunset, about one-half kilometer from a field station in Costa Rica, a young woman moved along a path taking notes and sweeping debris off of 1-meter square pieces of fabric pegged flat on the ground. The squares were spaced at intervals along the path for some distance into the jungle. She repeated her task at dusk and dawn. Her objective was to determine the relative importance of birds (active during the day) and fruit bats (busy at night) in seed dispersal. Each morning she identified and counted the seeds that had fallen on the fabric squares during the preceding night, presumably dropped from bats flying overhead. Then she swept the squares clean, and returned at sunset to tally seeds dropped by birds during daylight hours.

In another example, researchers in England used trace measures to investigate feeding habits of domestic cats. All but one of the households in a small village agreed to bag the remains of any animals that their cat caught. The researchers collected the remains weekly. They found that almost three-quarters of the prey of these domestic cats were small mammals. Contrary to what many people believe, birds were in the minority as prey except during the coldest part of the winter (when mammals stay below ground). Cats in houses near the middle of the village caught fewer prey than cats living near the edge of town.(5)

What do these photos reveal about behavior? (click ?? after you decide - the answer will appear in a popup message)

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Strengths and limitations

Traces are valuable for understanding animal behavior (as animals cannot be interviewed), and traces can be useful for offering hints about human activity. They may confirm information gained from other sources.

Most social scientists prefer to study live interaction rather than carpets and lawns. The information can be misleading. For example, deterioration of certain library books may reflect the activities of a single individual rather than indicate heavy circulation. In a building or neighborhood, the absence of graffiti may reveal more about cleaning policies than social attitudes.

To Summary

Footnotes
(1) Canter, D. V. (1994). Criminal shadows: Inside the mind of the serial killer. London: HarperCollins.
(2) Meeker, F. L. (1997). A comparison of table-littering behavior in two settings: A case for a contextual research strategy. Journal of Environmental Psychology, 17, 59-68.
(3) Goldsmith, D. S. (1994, April). Confidentiality in ethnography: Drugs, sex, and AIDS in the lives of informants in New York City. Paper presented at the 53rd annual meeting of the Society for Applied Anthropology, Cancun, Mexico.
(4) Webb, E. J., Campbell, D. T., Schwarz, R. D., & Sechrest, L. (2000). Unobtrusive measures (rev. ed.). Thousand Oaks, CA: Sage.
(5) Churcher, P. B., & Lawton, J. H . (1989, July). Beware of well-fed felines. Natural History, 40-7.