English 論文/Paper

The suggestion of evidence-based Romantic Love theory.


①The current state of Japanese Romantic Love

At first, as the above figure, about 70% males from 20 to 30 years old in Japan have no girlfriends. On the other hand, above 60% females from 20 to 30 years old in Japan reported that they had no boyfriends.(ブライダル総研2015).

According to this report, the young people in Japan do not think the romantic love important. It is the severe problem because of the declining birthrate in Japan. Thus, it is not exaggerated that all we need in Japan is to deepen the research of the romantic love or to develop the romantic love theory. If the young people do not love, the falling fertility rate and the aging becomes more serious. This is the emergent problem for the Japanese government.

Instead of this situation, however, the past research of the love has never made progress. Matsui(1998) claimed that the literature and the fiction are the main subjects to be investigated. The magazines for adolescents frequently focus on the romantic love and inform how the other sexes think or how people can get along with them. But, almost all the articles in those magazines are the comments or the experiences of the popular cerebrity or the commentators. These articles are not evidence-based. Occasionally, the magazine and TV show the data, which is composed of the simple interview or is the questionnaire. Tanimoto (1998) investigated the articles about the romantic love in those magazines and showed that these were far from the actual romantic love theory because the authors wrote them to make readers pleasure and avoided the suggestive conclusion in order to appeal to readers.

In sum, the past romantic love theory is based on the subjective perspectives. It is a pleasure and not "the Theory" but "the Perspective". If you claim the romantic love theory, the universality and the evidence are needed in the theory. The past romantic love theories are less evident and fruitless by saying "The love is ...etc" to avoid the solid conclusion.

②The current Romantic Love research

However, one of the reasons why the past romantic love theory is there is lack of the scientific research. In fact, the start of the scientific method particularly by reference of psychology is 1970 years. Before 1970s, psychologists examined the love as "Attractiveness". Researchers investigated enthusiastically the love by means of scientific methods in 1970s. Why is the scientific research so late ? First, the definition of the love is too broad. Second, there are ethical limitations. Third, when a researcher chose the love as his/her research target, he/she was not recognized as the scientist and he/she can not gain the research funds. More seriously in Japan, researchers started to investigate the love in 1990s(Matsui, 1990; Matsui, 1998; Matsui & Hiko, 2005). In neuroscience, the start was later because introducing PET and fMRI was about 30 years ago.

Although the research of the romantic love is developing, I will show you the evidence-based romantic love research and give you the foundation to think and discuss the romantic love. I claim the scientific romantic love theory.

The purpos of this article is to answer the main question "Why do we love others" by reference to psychology, neuroscience and evolution.

Before, we must be supposed to understand the difference of the two explanations. Kartlite(2005) suggested the way of the two explanations: the close-range explanation and the ultimate(long-range) explanation. The former refers to the direct causal relationship with things. The latter deals with the essential causation of things. For example, for heart attack. The close-range explanation is the decline of blood flow into the myocardium. The ultimate explanation is the lack of nutrition, the stress, or the genetic abnormality. In this article, I suggest the ultimate explanation of the romantic love.


③The definition of Romantic Love

By the way, I will define the romantic love. The romantic love has been studied by "romantic love", "mate choice", "sexual selection" in Psychology and Neuroscience.

We should differenciate "like" from "love". This difference was recognized by Rubin's classic research(Rubin, 1970). Bartels & Zeki (2000) used fMRI to show the difference of the brain activation whether the participants watched the girlfriend's picture or the unknown-other sex's picture. Marazziti & Canele (2003) investigated the difference of the blood hormones between "like" and "love". Thus, these are dissociable. But, we think these researches critically. Whether the participants do sex or not has possibly great influence on the change of brain activities. Although the limitations are there, these researches made a progress on unveiling scientifically the romantic love.

Fischer et al. (1998) divided "love" into the three types-"Lust", "Attraction", and "Attachment". "Lust" is the sex drive and satisfies sexual needs. "Attraction" is lively emotion. People who has "Attraction" think someone several times and wish for the affective relationship with them or the partner. "Attachment" is the comfortable emotion and it maintains the familiar social contacts. Thus, there are three types of love. Fisher, Aron, Brown(2006) inquiry that "mate choice" and "sexual selection" are common with "courtship attraction". The popular image of "Love" is nearly "Attraction". So, in this article, I define the Love as "Attraction".

Before I discuss the romantic love concretely, we take cousion for three things. First, the research I will introduce is what we are attracted to. Second, I want to introduce the neuroscientific research, but I will not do too specific to describe the research. If you are not the specialist for or study the neuroscience, it is not significant to

explain the brain region, the transmitter and the hormones related to the romantic love. So, I avoid to explain neuroscientific research. Third, I chose the understandable, interesting, and popular research. From three reasons, I introduce ①odor(pheromone)②looks③disposition.


First is the odor(pheromone). I introduce Wedekind's classic experiment. In supposition, I explain MHC(Major Histcompatibility Complex). The MHC is related to the immune system. The mouse has it, but the HLA(Human Leukocyte Antigen) is equivalent to it. The HLA has a variety of types like the blood type. Ihara(2002) described that the HLA type is so much that there is no man who has the completely same type. In other words, the type of the immune system depends on the human. The human can recognize the HLA differences as the odor variation and dissociate the HLA types. With this knowledge, I introduce Wedekind's research.

After checking the participant's HLA type, males wore the set T-shirts during two days. Then, females took the smell of the T-shirts and evaluated the odors. The results were that females evaluated better odors for males with different HLA types than males with similar HLA types(figure). Why do the female like the male with different HLA types ? Robetts & Roiser (2010) claim that the children whose parents have different HLA types have more flexible immune systems than children whose parents have similar HLA types, which results in sickless children. In other words, parents with different HLA types can leave excellent children.(We can reveal that the daughter dislike her father's odor.)


Second is looks. The main subjects are the shape and the face. On the former, Singh(2002) showed the WHR(waist-to-hip ratio)  for females is related to the attraction. According to Singh(2002), females with low WHR are more attractive than females with high WHR. Miller & Todd(1998) reported that in all culture the most attractive WHR is about 0.7. Why is the low WHR attractive ? Miller & Todd(1998) claimed that the low WHR indicated the health, the youngness, and the fecundity of the female. Moreover, Singh(2002) showed that the high WHR was correlated with the cancer and the psychiatric disease. In other words, the higher the WHR is, the weaker the female tends to be. (The discussion for face is as following blogs.)


Third is the disposition. Let me show you the figure by reference to Miller & Todd (1998).The figure show the disposition which is attractive for human. Geary et al. (2005) claim that the "cultural successful men"- who is in high social position and has many resources for their children and spouse- is attractive. They invest their resources in their children. Such children has low death rate and has more propagating power than other children. In other words, the men can leave excellent genes. It is more possible to make their children alive.

We looked into ①odor(pheromone)②looks③disposition. The common factor of these researches is that human are more attractive, who can leave their excellent children and make them alive. In conclusion, "Why do we love ?" is "to choose the human who can leave good children". We must stop discussing the unproductive subjective love theory. I suggest the Evidence-Based Romantic Love Theory.




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