This page is a collection of diagrams which map the historical development of L2 vocabulary research.
Some of the maps in this collection are based on a comprehensive analysis of all the data available in the VARGA database for a specific year. Other maps cover a number of years from the output of specific journals. The remaining maps are subject specific maps tht examine sub-topics within L2 vocabulary research
Click on the links to call up the map that you want.
Each map page contains a co-citation analysis of the specified data set.
The procedure for making these maps is as follows.
First we identify the literature that we want to analyse. In these maps, the raw data is usually a list of papers taken from the VARGA datbase. Bibliographies, monographs and theses are eliminated from this list, leaving us with a set of research papers that cover the relevant topic or time span.
Next we make a list of all the authors cited in each paper. Each author is listed separately, and co-authors all receive the same weight. Authors citing themselves are not penalised. From this author list, we can construct a list of co-citations - i.e. a list which identifies pairs of authors who are cited in the same work.
After this, we count the number of times a co-citation appears in this list, and eliminate the co-citations which appear only rarely. This simplifies the displays generated by the next procedure. We normally set the threshold for inclusion so that about 100 authors appear as nodes in the maps. For the very early work, where fewer sources are availabe, a lower threshold has been set.
Following this preparatory work, the list of eligible co-citations is submitted to GEPHI (http://gephi.org). GEPHI performs a cluster analysis on the co-citation data and generates a map which shows the relationships between the clusters. Each cluster consists of a number of authors who are frequently cited alongside each other. The clusters represent "invisible colleges" in the research community - a group of people who share common research interests. The specific focus of each cluster can usually be established by identifying the cluster members who figure in the largest number of co-citations for that cluster.
Finally we note the salient features of each map, and interpret their significance. Each map is accompanied by a short account which notes the principle clusters it contains, and who make these clusters up. The notes suggest how the clusters might be interpreted, and identify the significant researchers in each cluster.
In the long term, I am intending to produce a whole series of maps of this sort, one for each year between 1982 and 2012. I am also investigating other bibliometric sources for looking at vocabulary research. Specifically, I am developing some large scale maps based on the research appearing in some long-running journals. This will allow me to plot the appearance of research fronts and the emergence of research priorities over the whole of the 20th Century.
If you are interested in collaborating with this work, please contact me.