I think more important is the mental age. If someone is mentally young even at the age of 70+ then he/she can contribute almost as a young one.

You can contribute till your brain is fertile, no matter what is the age.

This is an interesting question. I plugged "age and research capabilities" in Google that produced several responses you may want to consult. One contained the comment "you're as old as you feel." This highly variable respnse suggests that there isn't a "best age". Neuroscientific research has demonstrated that neural plasticity is a factor in brain physiology that makes learning through change in experience possible no matter the age even when there is a trauma such as a stroke. The answer to the question probably relates more to ontogenetic and phylogenetic endowment than another variable.

At least from my experience: yes, age affects a researchers capabilities. But not because of biological reasons (maybe on a really high age). In my field, most research is done by PhD-students and PostDocs, or people between 25 and 35, roughly. When they get tenure or establish themselves on high positions in academia, they do less research - but publish more. For that reason, most publications in sociology etc. are theoretical ones, only accepting reality as a "case" or an example. And I have the impression, that this tendency gets clearer, the older the researcher gets: at the end of their academic carrier, they will want to write "one last big book" on their field of interest - a book that of course does not contain any empirical research at all.

So, I do not think, this has to do with age as a biological phenomenon, but with the concrete perspectives and possibilities within academia. I also think that this trend is highly problematic and threatens to turn social sciences into a complete irrelevant field that no-one outside of them understands.

Dear Sahifa

It is well documented that aging is associated with cognitive declines in many domains. Yet it is a common lay belief that some aspects of thinking improve into old age. Specifically, older people are believed to show better competencies for reasoning about social dilemmas and conflicts

I suggest reading the article:

Reasoning about social conflicts improves into old age

Igor Grossmanna,, Jinkyung Naa, Michael E. W. Varnuma, Denise C. Parkb, Shinobu Kitayamaa, and Richard E. Nisbetta,

Department of Psychology, University of Michigan, Ann Arbor, MI 48109; Center for Vital Longevity, University of Texas at Dallas, Dallas, TX 75235

Thank you Nelson, Anam, Phillip and Thomson.

Generally speaking I would support Anam's comment. If I remember it right Ancient Greeks considered the best age about 40, probably as the optimal ballance between flexibility and gained experience, often probably gained in a hard way.

I think more important is the mental age. If someone is mentally young even at the age of 70+ then he/she can contribute almost as a young one.

You can contribute till your brain is fertile, no matter what is the age.

I would think emotional maturity and intelligence plays a key role in in-depth interviewing.The manner in which researchers present themselves to participants has potential to determine the quality of responses from participants. Confidence without arrogance and mutual respect between all parties is essential in qualitative research. We do research "with" not "on" participants. It is also important to maintain humble approach to knowledge as this has potential create power imbalance between the researcher and the researched.

It is an indisputable fact that with advancing age the person acquires many developmental skills, but also observed degradation of biological, anatomical, cognitive, emotional, social, communicational functions. But there are limitations that do not affect the cognitive and emotional dimension, which are what I consider essential for anyone including an researcher maintain its scientific activity that is also creative and passionate. And this is the central point I wish to emphasize. The regular practice of intellectual reading, writing, drafting, analysis ... that researchers do for years was established as protective factor against the effects of aging.

Unless a serious disease that affects the brain level thinking and feeling occurs, the elder researcher accumulates immense wisdom, a workout of intense production, an indisputable methodological domain, an amazing insight to define phenomena of study.

Given the experience and knowledge that older researchers owns, the flaws which might have are easily remedied, and allows young researchers to contribute and complement which is also good!