The position held in the list of authors really depends upon your discipline. In the humanities, usually the first author provided the largest contribution and therefore receives the highest credit. In terms of tenure applications, first authorship is highly valued. However in medicine and health disciplines where research teams and authors work in large groups of sometimes over 6 authors, each author receives equal credit and in fact the authors may only be listed in alphabetical order. I've noticed journals recently asking for the type of contribution each author has made, whether it is substantive content or minor editorial work. So although for many years the convention was that the first author was the driver of the writing and the research, things may change in the particular journal your submitting to. It's always best to ask. The last authorship is sometimes a sign or token of gratitude provided for a thesis supervisor or research partner who had little to do with the development of the ideas and methodology, however this person was instrumental in providing access or opportunity to conduct the research. I hope this is helpful.

The position held in the list of authors really depends upon your discipline. In the humanities, usually the first author provided the largest contribution and therefore receives the highest credit. In terms of tenure applications, first authorship is highly valued. However in medicine and health disciplines where research teams and authors work in large groups of sometimes over 6 authors, each author receives equal credit and in fact the authors may only be listed in alphabetical order. I've noticed journals recently asking for the type of contribution each author has made, whether it is substantive content or minor editorial work. So although for many years the convention was that the first author was the driver of the writing and the research, things may change in the particular journal your submitting to. It's always best to ask. The last authorship is sometimes a sign or token of gratitude provided for a thesis supervisor or research partner who had little to do with the development of the ideas and methodology, however this person was instrumental in providing access or opportunity to conduct the research. I hope this is helpful.

The authors of a study 2nd, 3rd or so other than the primary author (who contributes maximum) are the contributors of the study. Listing the authors can be in alphabetical order, seniority level or depending on the amount of contribution to the research, if not a case of gift authorship (commonly practiced).

You can go through the following article for a detailed understanding- Author Sequence and Credit for Contributions in Multiauthored Publications - at

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1769438/

You can also look to another similar discussion in RG

https://www.researchgate.net/post/Does_the_order_of_authors_in_an_article_follow_certain_guidelines

Generically, the author order is based on the contribution of the each to that particular study. But it needs careful intrepretation based on the type of discipline where each author belongs. Mostly, the Statisticians and other supportive personnel will be placed either as third or fourth author in any research (other than Statistics related research) since their contribution is mandatory irrespective of the field of research. In interdisciplinary research, the first authorship will be given to the author who belongs to the major discipline of study.

In my opinion, the arrangement is based on their contributions.