The article should not have been published because an average 5 year old could come up with the study. Anyways, psychology is a soft science so I a not surprised that garbage like this got published.
That's not really the point, though. The purpose of carrying out the experiment was to obtain a concrete answer to something that we all just shrug at and
think we intuitively know the answers to.
Now we have solid evidence that human females find brown eyes more trustworthy. That is a usable statement. Before, we could have said "we think that brown eyes would be considered more trustworthy" or "I find brown eyes more trustworthy", but it would have been solely conjecture. Now, is this something that will be useful in the future? Maybe, probably just as much as the factoid that "symmetry" is attractive.
Science
should always strive to provide solid evidence for statements generally assumed to be true, and while this study is not useful on its own, there's no guarantee that some later researcher won't stumble upon it and think "this is just what I was looking for" and include it in something more applicable.
As for your claim that 'A five-year old could have come up with this study'...yeah, that may be true, but these people actually got approval, carried it out, and got results. There are plenty of groundbreaking studies that you can look at and think "hey, a kid could do that" (heavier objects don't fall faster, anyone?) but publications aren't awarded by who
could have done them, just who
did. First.
Furthermore, PLoS is a journal set up SPECIFICALLY to publish results which are currently non-publishable due to a lack of impact. This is actually hugely important, because our current, impact-based system of publishing, is profoundly flawed.
For example, negative results don't
do anything themselves, and so don't get published. But think of it this way: one researcher tries 16 different ways to achieve a goal, and all of them fail. He can't publish negative results, so he moves on.
The next researcher in the field comes up with ~12 different things to try, but 10 of them have
already been tested by researcher A, and we know they won't work. This goes on worldwide, with countless postdocs laboring away at efforts which, if impactless negative results were published somewhere, they would already know were futile. This is SUCH an enormous waste of manpower, resources, and creativity that it is not even funny.
In the case of medical trials, it can move from 'not funny' to 'deadly'.
Look up Ben Goldacre's TED talks on bad science.
TL;DR
Simplicity does not make an experiment worthless
We SHOULD be collecting evidence on basic assumptions
PLoS is not a 'crap' journal
Impact-less studies, especially negative results, REALLY NEED be published, and PLoS is trying to make that happen.