Because all good research is designed to build on and expand existing knowledge, it would be wasteful for a scientist to begin working on a project without knowing what others working in the area have already done. This is why scientists receive years of training in which they learn both methods of conducting research and the current content of knowledge in their fi eld. It is also why scientists spend a lot of time reading about research in scientifi c journals and participating at conferences where research is presented. In short, scientists are keenly aware that their research will make a contribution to the fi eld only if it is based on and adds signifi cantly to what is already known.
Once you have begun to develop an idea for your research, you should perform a literature search to locate the research articles and books that contain reports of previous research (Reed & Baxter, 1983). Conducting a literature search before beginning a research project is essential because it helps prevent duplication of effort and may help you avoid problems that others have had. The literature search is also a great time-saver because it can provide you with invaluable information about how to measure the variables you are interested in and what research designs will be most useful to you. There is so much literature in behavioral science journals and books that no matter what your research idea is, others will probably have done something relevant to it. This does not mean that your idea is not important—in fact, it suggests that others have also found it to be so.
Locating Sources of Information
There are many sources of research literature relevant to your interest. Probably the most important sources of information are research reports that contain complete descriptions of the collected data and the data analyses. These research reports are known as primary sources and usually appear in professional journals. Secondary sources are documents that contain only summaries or interpretations of the research reports rather than a complete description of them. Secondary sources include textbooks, books written by a single author, and edited books that contain a collection of chapters on a single topic, each contributed by a different author. Some journals, such as Psychological Bulletin and the Annual Review of Psychology, also publish primarily secondary-source articles.
In most cases, the sources that you locate can be found online through the databases maintained by university libraries. If the source is not online, you will have to fi nd it on the shelves of your library using the call number of the book or journal. If your library does not subscribe to the journal or have the book on its shelves, you may be able to get it through the interlibrary loan system. You may also wish to use the Web to get ideas. It is likely that no matter what your topic is, you will find one or more Internet sites that contain data and other relevant information about it. This material might include newsletters, unpublished research papers and reports, and online books and brochures. These sites may be particularly helpful for getting new ideas and for seeing what other people interested in the problem are doing.
One potential problem with web sources, however, is that the information may not be very objective. There are many websites that espouse views of the authors without much fact checking or verifiability. Thus, some web information may be based primarily on intuition rather than on data or facts. It is up to you, as an informed consumer of information, to do the very best you can to determine the validity of the information in the sites that you find. Some sources, such as www.scholar.google.com are reputable sources of academic information. And many academic journals can now be found on websites at your university. Other sites may be less valid. As you attempt to determine the validity of the information on the sites you fi nd, keep in mind the distinction between primary and secondary source information, and ask yourself about the likely source, credibility, and currency of the site. Is the information based on scientifi c research or is it more value-based? Both types of information can be informative, but a good scientist attempts to determine the difference. If you do decide to use information from web-based material, be sure to accurately report the source of this information in the Reference section of the manuscript.
Other valuable sources of information are experts in the fi eld in which you are interested. An instructor may be a good source in this regard or may be able to direct you to an even more knowledgeable expert. Experts can also be useful in directing you to specifi c journals that are known to contain the best published research in your topic area. Do not be shy about contacting experts. Although they may be busy, scientists are usually happy to put their knowledge to use.
Conducting the Search
Generally, a literature search will be most efficient if it (1) starts at a broad, general level (secondary sources) and then progresses to more specific levels (primary sources) and (2) starts with the newest available information and uses this information to progress backward toward previous research.
One approach to beginning a literature search in an area that you do not know much about is to use one or more introductory textbooks in that field as the most general secondary sources. Choose a chapter in which your topic is discussed, and read the chapter carefully. Although using secondary sources can be a time-saver because they generally provide more information in fewer pages, it is absolutely essential that you also consult primary sources in your literature search. Secondary sources may not adequately summarize the primary- source research. Journal articles are also more complete and objective than secondary sources because (as we will discuss in Appendix A), they have passed a rigorous review process.
After you have begun to focus on a topic area, you will want to move from general information toward more specifi c treatments of the topic area by reading book chapters and journal articles. As you begin to move deeper into your topic, do not be too infl exible about what you are interested in. It is best to keep an open mind at this point because you may fi nd that your research idea has already been well tested or that another research idea interests you more than the one you began with. Remember that your goal is not only to read about the research but also to use the research to develop and refi ne ideas for your own research. Being open-minded is important in all stages of the research process, especially because research that originally seemed irrelevant may later turn out to be valuable to you when you have a broader idea of the scope of the topic you are studying. The literature search should be used to help you modify and refi ne your
original ideas.
Investigating Computer Databases. The most efficient way to find primary sources relevant to your topic is through the use of a computer-aided literature search. Behavioral science databases are provided by most libraries and are available online. The databases contain summaries (called abstracts) of thousands of journal articles and book chapters. Reading these abstracts will give you a basic idea of whether the material will provide information you are interested in, and where to locate a journal article or book chapter if you decide to read it.
The most relevant database in psychology is PsycINFO®, which indexes almost 2 million references to psychological literature published from 1887 to the present. Many of these articles will be online in your library. The American Psychological Association website (www.apa.org) has more information about this database. Similar databases are found in other fi elds. For instance, SocialSciIndex® is a sociological database containing abstracts from over 1,600 journals. Medline® indexes journals in the areas of health care, environmental health, and behavioral medicine, and ERIC® is a collection of databases including those related to education and training.
Another useful database is the Social Science Citation Index (SSCI). Although the normal search procedure is to use the reference lists of newer journal articles to locate older articles, SSCI allows you to work the other way around. If you have an older article that you have found to be very important to your topic, you can use SSCI to fi nd other, more recent articles that have cited that article in their references.
Using Keywords Effectively. Before beginning your search in a database, you will need to have a few keywords to use in locating your materials. Most of your keywords will be of subjects, such as learning, memory, stress, or paranoia. However, you can also use author names or journal titles as keywords. You can develop your own keywords on the basis of your interests, but if you are not sure about what keywords to use, consult the Thesaurus—an index of all of the keywords used in the database. Ask your reference librarian for help if you are unsure how to proceed. Once you have entered a keyword, the computer checks the titles and abstracts of all of the books or articles in the database for the occurrence of that word. One problem is that some keywords are so broad that there are far too many articles using them. For instance, I recently searched PsycINFO® using the keyword learning and found over 182,000 journal articles listed! The database thus allows you to combine keywords to make your target more specific. For instance, when I combined the keywords learning and children, the list was reduced to about 31,735 articles, and a search for
learning and children and television produced only 278 articles. Finally, I indicated that I wanted only articles from the years 2000–2002, and this reduced the output to a manageable list of 28 articles. You can also limit
your search to include only journal articles, to include only certain authors, and (in case your foreign language skills aren’t that good) to include only articles in English.
Figure 2.1 shows the input that I gave to my search. You can see that the database is PsycINFO®, that there are three keywords—children, learning, and television—and that I have indicated to search only in the years 2000–2002. Figure 2.2 presents the first listing that came out of my search, and you can see the type of information it contains. It includes the title and authors of the article, as well as their university affi liations. Also included is information about the journal in which the article is published and the abstract. The listing also allows me to see whether the article is available in my library and whether it is available online. In this case, the full text of the article turned out to be available, and I could go right to reading it. 
Using the keyword system will get you started, but it is only the beginning of your literature search. As you read journal articles, you will fi nd that those articles contain other relevant articles in their reference sections. Working backward through the reference lists of the articles you read will allow you to fi nd many new articles that did not appear in the initial keyword search. To adequately prepare a research topic for investigation, you must do an extensive search of the literature, which will take quite a bit of time. Keep in mind that you can often do a large part of the preparation for your research project at this point by taking good notes or making copies of the articles and by thinking about how these references will relate to your fi nal report.
Using Abstracts to Select Important Documents. Once you have developed a smaller list of articles relevant to your area of interest, you will begin to read their abstracts to determine if the articles may be of interest to you. As you read through journal abstracts, you will probably fi nd that there are certain authors who have published frequently in your topic area. These are the scientists who have made major contributions to the literature, and you may wish to locate their contributions by entering their names as keywords.
Remember that it is important to read at least some of the articles that you have located. It is not suffi cient to just read the abstracts, because they are too brief to give you a complete understanding of the research.
