Depends on the incident.
You can apply it to people doing nothing in a serious situation, and I highly doubt people would come forward if this effect were enacted. The way it works is we become so desensitized to such actions we don't feel it is important to do anything about it or report it.
The answer to this question is <span>Longitudinal Study
The main purpose of this type of study is to find out whether a certain variable will give different response if the time factor is change.
Examples of this time of study would be: a sudy to find out how long it need for a certain viruss to develop if it got injected since early age.</span>
