Our weekly round-up of the best psychology coverage from elsewhere on the web

Recent years have seen a proliferation of mental health apps that claim to help relieve symptoms of depression. But there’s not much evidence that they really do anything, writes Tom Chivers at Unherd. Even in the few cases where there has been research into the effectiveness of the apps, the studies are often small and uncontrolled, raising questions about how solid the results are.

Ever felt like pop songs are getting sadder? Well, you’re not wrong, according to researchers Alberto Acerbi and Charlotte Brand, writing at Aeon. The pair analysed more than 150,000 songs released between 1965 and 2015, scanning the lyrics for words related to positive and negative emotions. Over the years there was an increase in the use of negative words, and decrease in positive ones. The team suggests that this is a result of “cultural evolution”: songs with negative emotion words tended to be more popular, and so in subsequent years songs contained even more negative lyrics.

Could war crimes be prevented if the military were to screen recruits for specific personality traits? In The Conversation, researchers Magnus Linden and David Whetham report that elements of the “dark triad” of personality traits were found to be related to unethical behaviour among peacekeepers. “It may be inevitable that atrocities happen in war”, they write. “But that doesn’t mean that some, or even many, ethical violations could not be prevented. To do this, we have to take more notice of the evidence that we have available.”

Concerns about the effects of smartphones and other technologies are increasingly in the headlines. But what does the evidence say? Amy Orben, research fellow at the University of Cambridge, talks to The Guardian about her research into digital technology and the wellbeing of young people. We talked to Amy in our latest PsychCrunch podcast — if you haven’t heard it yet, check it out here.

And when it comes to concerns about technology, there are also matters of race and privilege to consider. In The Conversation, Emeline Brulé and Matt Rafalow report the results of their study looking at the way teachers from different schools perceive students’ use of digital technology. Teachers from a private school with mainly white students tended to see technology use as beneficial to the kids’ education, while those at schools with more marginalised students were more likely to perceive it as simply “messing around”.

We already knew that toddlers can be surprisingly selfless — but a new study has found that even babies as young as 19 months display altruistic behaviour. Babies willingly gave a piece of fruit to an adult who clearly wanted it but was unable to reach it, report Sandee LaMotte and Kristen Rogers at CNN — even at meal times, when they themselves were hungry.

Finally, a viral tweet questioning whether we all have an inner monologue led to this story in Mic from Tracey Anne Duncan. Psychologists agree we all have “self-talk”, Duncan writes, but this doesn’t have to involve words — it also includes imagery and sensations. And what’s less clear is exactly how the content of that self-talk reflects our mental health. (Whether we all hear a voice in our head when we read is another question — something we covered back in 2016).

Compiled by Matthew Warren (@MattbWarren), Editor of BPS Research Digest