"Age and the Trying Out of New Ideas"-Initial Impressions

Feb 18 2015 Published by under Uncategorized

Alerted by a post on Nature News and Comment, I read with interest a newly posted paper from Mikko Packalen and Jay Bhattacharya from the National Bureau of Economic Analysis entitled "Age and the Trying Out of New Ideas."

The abstract of this working paper states:

Older scientists are often seen as less open to new ideas than younger scientists. We put this assertion to an empirical test. Using a measure of new ideas derived from the text of nearly all biomedical scientific articles published since 1946, we compare the tendency of younger and older researchers to try out new ideas in their work. We find that papers published in biomedicine by younger researchers are more likely to build on new ideas. Collaboration with a more experienced researcher matters as well. Papers with a young first author and a more experienced last author are more likely to try out newer ideas than papers published by other team configurations. Given the crucial role that the trying out of new ideas plays in the advancement of science, our results buttress the importance of funding scientific work by young researchers. (Emphasis added)

Needless to say, I was intrigued. After a quick read, I looked deeper into the methodology, particularly with regard to the highlighted terms above.

The study is based on the use of MEDLINE (accessed through PubMed). More precisely, they used “Author-ity” MEDLINE, a previously constructed version of MEDLINE with the names of authors disambiguated as much as possible. This database was used for two purposes. First, new ideas were identified by searching titles and abstracts for two- or three-word strings and associating these with the year when they first appears. Strings that subsequently occurred with high frequency were deemed to be important new ideas. The Nature commentary includes a list of the ten most frequent concepts for each decade and inspection reveals these to be sensible. Second, the "age" of each investigator was estimated by determining the year in which the first publication by this investigator appeared. Thus, this is "career age" rather than chronological age. This is a sensible approach which has both advantages and disadvantages. Most importantly, it is workable from the available data. I know from some of my recent analyses, estimating chronological ages of investigators can be quite difficult. In addition, this automatically at least partially corrects for increasing training periods over time. A disadvantage is that an early publication can "age" an investigator compared to peers.

With these two parameters, the authors were set to do some analysis. Figure 1 in the paper is shown below:

Screen Shot 2015-02-18 at 8.28.34 AM

Panel A shows the fraction of publications trying out new ideas versus the career age of the first author. Clearly, there is a broad peak in which the first authors are within 3-12 years of his/her first publication. This, of course, primarily reflects the accomplishments of graduate students and postdocs!

Panel B shows the comparison for All Authors. This shows a more featureless downward trend. This probably reflects the contributions of graduate students and postdocs but with more senior members of the research teams in the mix.

Panel C shows the distribution with Key (both first and last) Authors. This shows a peak in the career age range of 10-15 years. Given the first author distribution from Panel A, this suggests that the last author distribution has a peak around 20 years. This is confirmed by the data presented in Figure 3 which shows the data in two-dimensional format with Career Age of Last Author versus Career Age of First Author.Screen Shot 2015-02-18 at 8.37.45 AM


The maximum for this post occurs with first authors with career ages between 1 and 10 years (i.e. graduate students and postdocs) and last authors with career ages between 8 and 25 years (early to mid-career faculty).

Does this mean that early to mid-career investigators are the most productive in trying out new ideas? Yes and no. As a population, they certain do appear to be. However, these data have not been normalized (as far as I can tell) to the distribution of the ages of investigators. This distribution (which has been changing over time as we were recently reminder by Drugmonkey) shows peaks (both for R01 grantees and medical school faculty) in the range of 45-55 years old over the period covered by this analysis.  If one assumes an age of the beginning on independent careers of 36 (over this period not just at present), the data are consistent with the number of faculty at each career stage being an important factor.

Overall, the paper clearly supports the roles of graduate students and postdocs in being first authors of many (most) papers that appear to break new ground. This is, as George Carlin would say, "near-fetched." The results regarding last authors will require a more careful reading of the paper and, perhaps, more analysis by the authors. However, this is clearly an important data set and approach to provide empirical evidence that bears on these important issues.

6 responses so far

  • Woman in Stem says:

    "Overall, the paper clearly supports the roles of graduate students and postdocs in being first authors of many (most) papers that appear to break new ground."

    I guess I'm a little confused. Isn't it customary in biomedical science to list your grad student/postdoc 1st and yourself (PI) last, regardless of who it is that actually comes up with the groundbreaking idea? Aren't grad students/postdocs 1st authors of most papers in biomedical science, period? (Not a fan of George Carlin, so not sure what "near-fetched" means.)

    • datahound says:

      Sorry for the obscure reference. Yes, grad students and postdocs are 1st author on most papers in biomedical science in general and, therefore, it is not surprising that they are first authors on papers with new ideas.

      The George Carlin reference is about the absence of opposites of some common words/phrases. The opposite of "far-fetched" is "near-fetched", that is, obvious.

  • Anne Carpenter says:

    Love your analysis, and the title "initial impressions".

    I've not had time to thoroughly digest the article and I love how data-driven their analysis, but I suspect there are a lot of interesting tidbits amongst this data. Your point - that the demographics are not even across these career age ranges - seems important for proper interpretation.

    Thinking out loud here... Career age of FIRST author is especially puzzling. I guess the fact that the peak is <10 is saying that graduate students and (early) postdocs are more likely to be using novel techniques as compared to older first authors. Not shocking, I suppose. But who are these "older" first authors? Generally, there should be few such people since NIH science is largely driven by trainees (in the pyramid scheme that is modern US science). So anyone "older" (aka later career stage) who finds him/herself in first authorship is likely a relatively small fraction of the overall researcher population and I'm wondering if this type of article is special in some way that explains the lack of cutting edge research techniques. The study does exclude review article types, which would've been my first hypothesis. Hmmm. I am a bit biased against the blanket idea that young people are more innovative overall, but I suppose I can believe that "older" researchers have less opportunity to learn brand new techniques perhaps because of career immobility (vs grad students and postdocs who change labs every few years and are more likely to pick up new techniques and ideas).

    Regarding last authors, this also puzzles me. One would think that "older" senior scientists could attract the cream of the crop, so that grad students and postdocs joining their groups bring in novel techniques and ideas.

    Would love to hear others' thoughts on this.

  • Woman in Stem says:

    I dunno. The way I read this is that the most innovative work is being done by tenured mid-career folks (with their grad students/postdocs as 1st author) who are precisely the ones that can afford to take such risks. Hardly surprising.

  • Crystaldoc says:

    This is an interesting study, but as Anne C. Points out, I think there will be some confounding variables, relating to different types of papers inhabiting different spots of first-last author geography, due in part to differing authorship conventions across fields and types of studies, that make interpretation difficult. Interpretation may be relatively straightforward when comparing only papers from lab-based groups with a single PI on the paper, but once you roll in papers from collaborative groups and consortia, what constitutes first and last author will change along with the type of paper. I have seen that in a clinical setting, junior trainees will be first authors on smaller papers that may explore newer topics, but ultimately be considered of lesser "impact", while a huge consortium study like a drug trial, by its nature may not be using the newest catch phrases, and by its nature will feature very established clinicians in both first and last author positions. By trying to analyze all these papers together as one homogenous body of data, I fear we may draw possibly flawed conclusions about the age-predicted creativity of the scientists involved.

    I would also point out that the bottom few rows of the last figure (very early career age of last author) are unlikely to represent papers in which the last author is a position of seniority, although this looks to be of minor concern overall to the analysis.

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