What’s the difference between studying a subject extensively and studying it intensively, between doing extensive research and intensive research? It seems like a simple enough question, one that could easily be answered by consulting a dictionary. I consulted four: Merriam-Webster Unabridged (3rd ed), The New Shorter Oxford English Dictionary, Webster’s New World College Dictionary (4th ed), and The American Heritage Dictionary (5th ed) .* Here’s what I found:
Intensive = intense; highly concentrated; thorough; exhaustive
Extensive = large in extent, range, or amount; far-reaching; comprehensive; wide
You can see that in some senses, the two words seem like antonyms (compare “highly concentrated” and “wide”), whereas in other senses, they are nearly synonymous (compare “exhaustive” and “comprehensive”). Perhaps not surprisingly then, I find that scientists who are not native English speakers sometimes have trouble with these two words: specifically, they use “intensively” where I would expect “extensively.” (I can’t say that I’ve ever seen the opposite, and it’s worth noting that a search of Google Scholar reveals that “extensively” is used more than three times as often as “intensively.”) I wouldn’t go so far as to say that this constitutes an error, but why not preserve a useful distinction between the two words?
I suggest using “intensively” when referring to in-depth research involving intense effort narrowly focused on a specific issue and perhaps conducted by a small group of researchers. In contrast, use “extensively” when describing comprehensive research covering many aspects of an issue and perhaps conducted over a relatively long period of time by numerous research groups.
Here are some examples of what I consider to be idiomatic uses of these two adverbs:
At an intensively studied site within the region, >90% of the dominant overstory tree species died after 15 months of depleted soil water content.
The figure illustrates a typical spine synapse that makes intimate contact with an apical dendrite of a pyramidal cell. The ultrastructure of such synapses has been intensively studied in our laboratory.
Plasma membrane transporters have been intensively studied at the mechanistic, biochemical, and molecular levels.
The asymmetric aldol condensation has been the subject of intensive study in our laboratory.
The asymmetric aldol condensation is among the most powerful reactions in synthetic organic chemistry and has been extensively studied over the past 15 years.
As surrogates for the central nervous system, peripheral samples such as blood, saliva, and skin have been extensively used in psychiatric research for decades.
Because of its importance in cholesterol biosynthesis, HMG-CoA reductase has been extensively studied.
Undoubtedly, some subjects have been studied both intensively and extensively. Can both words be used in the same sentence? I found very few examples on Google Scholar. Here’s one:
One-dimensional ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications.
I’m not sure how I feel about that sentence. What do you think about it?
*Note that the first three dictionaries are considered to be descriptive—that is, they describe the language as it is actually used by native speakers; whereas the last is a prescriptive dictionary in that it provides some guidance as to how various usage “experts” feel that the language should be used. Unfortunately, it doesn’t provide any guidance about the difference between “extensively” and “intensively.”