This is a classic example of the kind of cherry picking and mis-application of research that I was guilty of when I worked as a researcher and writer for the Australian branch writing desk. If the article mentioned above was indeed referring to the same studies the Watchtower was referring to, all it shows is that Children had greater difficulty at physical regulation as similar aged children from 60 years ago. It says nothing about adults. It says nothing about moral or behavioural self-control - that is inferred without evidence by the commentary on the study. It is not saying that children are becoming more unregulated, at most it is showing that they are taking a few more years in age to become better at regulating themselves....
Neither the Watchtower, nor that article, actually references the original study so it is impossible for one to look up the methodology used to confirm wether the study was a good one or not (in terms of the number of participants, how they were elected, how the measurements were done, and how the data was interpreted etc)
Even if this study was of the highest calibre, this one isolated test alone does not prove a point, more research would be needed to show the results could be duplicated for starters and to provide more context and meaning.
To draw the very long bow that this study is proof of some "sign of the times" is extremely intellectually dishonest and nothing more than propaganda.
"Today's 5-year-olds were acting at the level of 3-year-olds 60 years ago, and today's 7-year-olds were barely approaching the level of a 5-year-old 60 years ago," Bodrova explains. "So the results were very sad."