An analogy would be to say that eating curry daily causes genetic birth defects, a common problem in immigrant asian (indian/pakistani/bangledeshi) communities. The birth defects are actually caused by the practice of marrying cousins often found in immigrants from the indian subcontinent, but if you were to ignore this and focus on people’s eating habits it would look as though lifelong daily curry consumption caused them.

The other problem with this research (I can’t find the original paper though, perhaps it never made it through to publication if it was as flawed as it sounds?) is that there doesn’t appear to be a control group for comparison. If they had compared the gang members to youths from similar cultural backgrounds and shown that gang members were much more likely to have played with pinatas as kids then I would be more convinced there was a real effect. But I strongly suspect that youths of a similar age, cultural background, income & neighbourhood would also have played with pinatas as children. The differences would probably lie in the way they were raised by their parents, their innate tendencies towards particular behaviours, their education, and intelligence. A well brought up kid with no particular innate tendencies towards aggression, impulsivity, addictive behaviour etc will be much more able to resist the lure of gangs than one from a more troubled family background or with a personality type that is attracted to criminal behaviour.

Having said all that, I wouldn’t be surprised if gang members had played with pinatas more often as kids, but with causation in the opposite direction to that which you postulate. Kids who enjoy smashing things up are inevitably going to enjoy pinatas more than a timid, passive, non-aggressive child, and will therefore probably have asked for pinatas at their birthday parties, would have been keen to join in with pinata games at parties, etc. You can easily see this difference between children playing with pinatas, some kids approach them with relish, smashing them as hard as they can and sometimes having to be prevented from continuing to allow others to have a turn, whilst other kids hold back, are more wary of the pinata, tap it gently with the bat, and don’t really seem very excited by them. The first lot of kids are more likely to be the hyper, boisterous types who start playfighting or getting out of control later at the party, whereas the second lot are the quieter, more gentle types who are likely to be found playing more sedate games. The pinata has not caused the difference between the two types of children, it just provides an outlet where their personalities become very apparent. The impulsive, aggressive, over enthusiastic kids will be that way regardless of whether there is pinata there, but they are the kind of kids who will enjoy using the pinata the most. These kids will then go home and ask their parents to have a pinata at their own party, thus perpetuating the impression that pinatas cause violent behaviour.

I’m sorry that you had such a bad experience with your daughter, but unfortunately it seems to have led you to view everything about pinatas through a very distorted lens. Confirmation bias is the tendency (exhibited by all humans) to focus on evidence that supports our point of view, whereas good science is based on seeking out falsifying information (essentially trying to prove yourself wrong). You are going out looking for every shred of information you can find that “proves” pinatas cause violence, but you’re not stopping to evaluate the evidence in a balanced way. Your site kind of reminds me of those “end times” fanatics who see proof everywhere that we are approaching the apocalypse!