Answer: Demand characteristics.
Explanation:
Demand characteristics are the traits shown by participant of the research and experiment in which they behave according to the expectancy of researcher or experiment so that aim of the research can be accomplished .This creates biasness in research process and decrease validity of the experiment.
According to the question, John's positive reply to the situation where someone need helps if his/her car is broken displays the impact of demand characteristics .In actuality , he would probably not help the person by stopping and he just answered in positive manner to support the study.Thus, the reply is biased.
The 2010s saw more people being born than the 1950s is true
