This is interesting, but personally I don't like these types of huge generalizations.. unless it can be proven to me that there's some sort of physical, biological reason as to why that happens. In my opinion, people experience different things, and all have different past relationships/experiences. I can say that I used to fall in love quickly, but as time passed it got harder to do so, or I looked for more things before deciding that I loved someone. Also, love to me, is an individual process. What someone thinks is love, might not be what someone else thinks is love. So when you survey people like that, you have to take into consideration the huge variability in definition.
So short answer, no, not sure I really believe this study lol