The children were not in any physical danger and were not harmed. I'm not aware of any research that shows that 3 minutes of panic for a 5 year old causes lasting psychological damage. Toddlers experience transient sobbing panic on a fairly regular basis for a variety of reasons. If they are comforted by supportive parents they are fine.

Since this study occurred in 1958, one could presumably find these kids today and see how they are doing. I'd wager that they are no worse-adjusted than would be expected of an average child of that era.