The concept explanation leaves a lot to be desired because generally two different people will have different concepts of the person being named, so how do those concepts get to the same person?
The ancient Babylonians had a very different conceptualization of the sun than modern astrophysicists, but the sensory experience is largely the same: big, bright light in the sky. Simple reference is derived from experiential evidence and not inferential chains of reasoning about the nature of something. Two people can have very distinct impressions about a third person's personality and behavior, radically divergent explanations about the person, but given the nearly identical sensory apparatus that two people share, it's hard to disagree on what they look like or repeating what the person says is their name. This is why my dogs recognize me and my name. They require no conceptual apparatus nor understanding of causality. They simply build up associations; sounds are paired with odor and sight. If I utter 'outside' suddenly, they dash to the door because outside refers to a chain of sensory experiences that have nothing to do with essences, definientia, or propositions.
That's not to say that reference can't involve more linguistically rooted analysis. Clearly the reference 'Avadgadro's number' IS conceptually rooted. But even in those cases, I've met a great number of people who can tell you what such a reference stands in for, and have very little idea of the conceptual apparatus of atomic and arithmetic theory that is relevant to make use of it. It's simply an orphaned fact from high school. "6.02x10^23!!!" they spurt out, happy to continue to make the association. They possess little to no knowledge of Boyle's Law, or little understanding of how PA forms the logical basis of the arithmetic that is used in calculations of molarity or molality. Here too, there's an association between one set of phonemes and another with some general notion that arithmetic is generally useful in stoichiometry. This is obvious to the intuitions that referring to things doesn't really require "conceptual or causal propositions" at all, so why the philosophical obsession with trying to prove it?
To those who defend embodied cognition (SEP), there are some folks like Plato and Frege who are to blame for this obsession. When you invoke concepts and causality, what you are citing in an indirect way is the method of using propositions to establish identity. Consider Dummett's thought on this:
It was Frege who first made identity a logical notion. The sign of identity differs from the other logical constants in not being a sentence-forming operator in the sense of one used to construct complex sentences from simpler ones, but a relational expression used to form atomic sentences. (p. 542, Frege: Philosophy of Language)
On page 544 he continues:
In Begriffsscrhift Frege held that identity was a relation between names and not between things... Later, he replaced this view...: identity could now be regarded as a relation between objects... without rendering the informativeness of identity-statements unintelligible.
In other words, reference and identity are now rooted in meaning-bearers called abstract objects. This is one way to interpret the notion of concept. From the SEP article of the same name:
This type of view has most prominently been associated with the view that concepts are Fregean senses (e.g., Peacocke 1992, Zalta 2001), so it is this version of the view that concepts are abstract objects that we will focus on here. For proponents of this view, concepts, as meanings, mediate between thought and language, on the one hand, and referents, on the other. An expression without a referent (“Pegasus”) needn’t lack a meaning, since it still has a sense. Similarly, the same referent can be associated with different expressions (e.g., “Eric Blair” and “George Orwell”) because they convey different senses.
But abstract objects and propositions are only one model of how cognition works, and other views might be more profitable. From earlier in the same article:
According to the abilities view, it’s wrong to maintain that concepts are mental particulars—concepts are neither mental images nor word-like entities in a language of thought. Rather, concepts are abilities that are peculiar to cognitive agents (e.g., Dummett 1993, Bennett & Hacker 2008, Kenny 2010). The concept CAT, for example, might amount to the ability to discriminate cats from non-cats and to draw certain inferences about cats.
In short order, then, the human ability to use references might be based, not on linguistic structures or abstract objects, but embodied intuitions, like facial perception. Facial perception is neither a concept-as-representation (such as a proposition) nor is it concept-as-abstract-object (yielding logical evaluations in truth conditional semantics), but is a cognitive intuition that is supplied by evolution at the neurological level far removed from language and logical quantification. Reference in these cases are an ABILITY native to the social mind. That's why chimps and dogs and parrots can use signs as references despite demonstrating no ability to use grammars or conduct explicit logical operations. In any case, sense and reference is a complicated affair, and the fact there are multiple notions of concepts, causality, and intelligence makes it hard to pin down reference to a single satisfactory explanation. It does seem, then, like a theory of truth, that we must take a pluralist explanatory stance.