The concept of "love languages" goes back to a book by Gary Chapman, and its popular understanding can be summarized as follows.
Each person communicates love via a preferred one of the so-called five love languages, which are: words of affirmation, quality time, gift-giving, acts of service, and physical touch.
I have grown opinionated on this idea and its use, and rather than bogging down any more casual conversations, I'd like to try expressing my response here.
The original claim is that each person has one primary and one secondary love language. In my experience, the more salient differentiation is not between primary/secondary/laters but between giving/receiving. For example, I often find myself giving though acts of service, but don't seem to expect them from others, whereas I tend to want words of affirmation more than I find it necessary to give them. This is a little too easy to fix to be a real criticism—we can just work with a version of love languages that distinguishes between giving and receiving, and acknowledges other context-dependence.
There are a couple more interesting pitfalls in the common use of the concept, however, as well as value in working through them.
Perhaps the most basic pitfall is to think that the point of the list is to diagnose oneself, and thereby know oneself. People seem fond to say "My love language is X", definitely, as a statement of identity. If this is fixed and determinative, then one is shielded by it from the responsibility to respond to circumstances: "I cannot, and therefore will not, give/receive love in language Y". Instead of the idea of love langauges serving our growth and agility, it is used to avoid these ends.
Yes, we have our sweet spots, but the point is less to know ourselves with certainty than to use that provisional knowing productively in the moment.
For example, there is already a powerful mechanism in the simple acknowledgement that people are communicating love in different ways. One person is giving love in one way, and another person is open to receiving love in their own other way. When these do not match, it is easy for the participants to assume that something is wrong, and to blame the other for not giving or receiving love as is desired. Naming the situation neutrally can disarm the scenario and enable either person to adapt how their love is given or expected.
Venturing into the abstract for a moment, this simplified drama is an illustration of a difficult lesson. When we view our situations through our personal and subjective perspective, the positions we take feel simply true. It is so easy to go through life with this perspective taken for granted, to then forget and eventually deny the aspects of reality that are obscured by it. Moreover, when our positions are in a clash with what is simply true to another person, it would seem that there is no common ground, no route to peace. When engaged in a contest of beliefs, the way out is something that seems utterly backwards: instead to recognize a bigger picture that includes the competing positions naturally, without judgment, as embodiments of the variety of the world. That bigger picture is then a space in which the participants are freed to productively work.
Another common pitfall, especially common in nerdy thinking, is to be concerned with the expressiveness or exhaustiveness of the list of languages itself, and to attempt to perfect it. For example, several people have suggested to me that the sixth love language ought to be play. This word would be broadly construed, including obvious games, as well as dance, flirting, and a general sense of invitation together into the yet-unknown. I happen to be rather sympathetic to this suggestion—it seems to me to cover a large amount of the situations that are missed by the original five.
But I still think that the "six love languages", or even the "thirty love languages", misses the point. There is no correct list. The list only provides suggestions to get you started in opening up to the multi-sensory variety of possibilities, in opening up to the actual circumstances. As I see it, the real lesson is to notice the meta–love language, which is the art of discovering and participating in the communication of love, however it might be expressed, in an ongoing process. When giving, this means to discover whatever makes another feel loved as the unique individual they are, to offer them exactly that, and to keep observing and adapting with the times. It is simply putting our full empathetic skills in the service of our compassion. When receiving, it means to learn a receptiveness to wherever love and support might be coming from. Doing so entails finding the source of love as a phenomenon within our own psychological experience, and connecting with it in the presence of diverse circumstances.
Venturing out once more, it might sound like hogwash in our modernist mindset to find that source of our experience of love, but means of doing so have been known forever, and can and should be named. You learn to visualize an entity that is fully seeing and loving you: your deity, your guru, your partner in intimacy, your dog, your parent, the parent you didn't have, your inner leader, or whatever is personally relevant to you. This is already you practicing loving yourself, albeit with a mask on to fool your defenses. As you study what it is like to feel that love directed towards you, you start to notice other ways you already love yourself, plus a growing openness to feeling love from everywhere else. At some point you've crossed the water and it's a big deal, but eventually you leave the raft behind and just go on with loving yourself, no big deal. Conversely, when we do not know how to feel for ourselves, our ability to receive love from others is compromised and insecure.
On the whole, the concept of love languages is a tool that I think I can put to use well, not only in immediately practical ways but also because the lessons around its pitfalls are valuable. The idea orients us towards appreciating our natural diversity as humans, and giving and receiving love exactly as it is.