Biblatex-apa style is missing a comma in the references. why?

Question

I have been trying to solve this problems for hours, but there is no solution in sight. Until a few weeks ago, my biblatex-apa style was working like a charm. Although, after installing the updates and Biber, the reference section became a problem. It should display a journal article by two authors with a comma after the first author, but it doesn't:

Weber, M. & Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002

it should look like this:

Weber, M., & Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002

This is how my document looks like:

\documentclass[12pt, onecolumn]{apa6}


\usepackage[utf8]{inputenc}
\usepackage[american]{babel}
\usepackage{csquotes}
\usepackage[style= apa, backend=biber]{biblatex}
\bibliography{testbib}
\DeclareLanguageMapping{american}{american-apa}


\begin{document}

Some text \parencite{Weber2012}.

\printbibliography
\end{document}

And the BibTeX file:

@article{Weber2012,
abstract = {},
author = {Weber, M. and Ruch, W.},
doi = {10.1016/j.adolescence.2012.06.002},
file = {},
issn = {1095-9254},
journal = {Journal of adolescence},
number = {6},
pages = {1537--1546},
pmid = {22749517},
publisher = {Elsevier Ltd},
title = {{The role of character strengths in adolescent romantic relationships: An initial        study on partner selection and mates' life satisfaction.}},
url = {http://www.ncbi.nlm.nih.gov/pubmed/22749517},
volume = {35},
year = {2012}
} 

I have tried various things so far, but none of it helped: e.g,

\renewcommand*{\finalnamedelim}{
\finalandcomma}

or

\renewcommand\finalandcomma{\addcomma}

Even in the biblatex manual, the reference examples of two authors is without the comma (it works for three or more authors). There should be a comma, according to APA6. Why is that comma not there? And how could I insert that into my references?

Answer 1

To force a comma in all cases, you are right to target \finalnamedelim. The correct version is

\renewcommand*{\finalnamedelim}{%
  \finalandcomma
  \addspace
  \bibstring{and}%
  \space
}

Answer 2

Actually, if you look at APA 6th 4.03 and also here:

http://blog.apastyle.org/apastyle/2011/04/using-serial-commas.html

You'll see that APA 6th edition style says serial commas are only for lists of three items or more. I changed the biblatex-apa style accordingly in version 5.5 and that's why you noticed the change. It's in the changelog for the style:

Fixed serial comma requirement (APA 4.03)

Answer 3

Actually, that link says nothing about any exception to the rule of serial commas for two authors. Indeed, the author strongly states a position that the serial comma btw last and 2nd to last authors, should remain.

However, the APA manual on p.88, 4.03, says exactly what you say it does. Commas only with 3 or more items in a series.

Jones, P. D., Johnson, L. B., & Johannas, A. B. (2014). blah blah blah

but we can infer that it should be:

Jones, P. D. and Johnson, L. B. (2014). blah blah blah