I seldom hear references from the genealogical community to the concept of cluster research. There is a lot more written about research logs, citations, writing reports, and the mechanics of recording than what you find written about the actual process of researching records. I view all those issues as a "grade school" level of genealogy. They are certainly things that you need to know and learn, but they don't produce information. They are like learning about the operation, function, and maintenance of an automobile, but never learning how to drive.
Anyway, since real research is seldom taught in the United States at the grade school or high school level, it is important that anyone getting involved in genealogy realize that there is a lot more to learn about the subject than the mechanics of processing information. You have to find it first.
There is a superficial resemblance between scientific research and historical research. But the difference between scientific and historical research is so fundamental as to make them entirely different pursuits. Unfortunately, the terminology used in referring to both is the same. Unless we branch out into archeology, historical research is basically the examination of the human written record. Overlaying this process of examining the written record is a significant amount of the personal interpretation and analysis that boils down to the opinion of the researcher.
One thing that all forms of "research" have in common is the need to determine whether or not someone else has already done the research you are planning to do. Since prestige in the scientific community is often based on the priority of a discovery, scientists quickly learn the need to do an exhaustive survey before beginning their research. Unfortunately, few genealogists feel compelled to survey what has and what has not been done and recorded previously. This subject reminds me of an experience I had one day while serving in the Brigham Young University Family History Library, I had a patron ask for assistance. She explained that she was in the last stages of certification from one of the two major certification organizations (which I will not specify) and she needed to know how to register for FamilySearch.org. I do not make this stuff up.
Genealogical DNA testing is seen as a way to make genealogical research more scientific and in some cases, when supported by adequate historical research, it may well dramatically influence the conclusions we make from purely historical research. DNA tests may also correct inaccurately recorded history. But long before DNA became a hot topic in genealogy, tools already existed to provide assistance in increasing the accuracy of our genealogical conclusions. Those tools are referred to as locality and cluster research.
Let's suppose you obtain a DNA test and as a result, you get a list of people who share some percentage of your DNA gene segments. We would have to further assume that many of your relatives had the same DNA test. Let's further assume that all of these relatives have their family tree online on the same website that sponsored the DNA tests. Does this begin to sound familiar? It should if you have been following the genealogy news. The CEO of MyHeritage.com, Gilad Japhet, has been speaking about this possibility for some time now. What you would likely see with an integration of DNA testing, historical research, and plotting together on a pedigree-like relationship chart, would be a cluster of people around you. If that chart also incorporated geographical and other information, you would begin to see patterns.
Cluster research, joined with locality research can produce similar results. As expressed by the Wikipedia article on Cluster genealogy:
Cluster genealogy is a research technique employed by genealogists to learn more about an ancestor by examining records left by the ancestor's cluster. A person's cluster consists of the extended family, friends, neighbors, and other associates such as business partners. Researching the lives of an ancestor's cluster leads to a more complete and more accurate picture of the ancestor's life.I would disagree with the article's definition in that cluster research is not a technique, it is a fundamental part of the research process. Presently, depending on the time depth, DNA testing may or may not help in this process.
Locality research is simply the process of adding geographic information to your cluster research. Granted, cluster and locality research are more involved and more time consuming than searching for names and dates, but they are really the only valid way to extend research beyond the simple search for names. Interestingly, many of the commonly used records are adjuncts to cluster research. For example, a census record is not just a list of names with some added information, it is also a snapshot of a neighborhood and a community. For example, I can go through the Census record of a small town and find a whole "cluster" of related people. The records available from and about those extra people may shed light on information that is missing about my own ancestors.
The article above from Wikipedia cites a good example of cluster research. Here is the citation.
Lenzen, Connie. "Proving a Maternal Line: The Case of Frances B. Whitney". Originally published in the National Genealogical Society Quarterly, 82, no. 1 (March 1994): 17–31.