Did you ever have an illustration for something just handed to you, so obvious that you didn't even have to think about it?
(one of the few videos I could find about The Dress that didn't include profanity)
"Perception of reality is not the same thing as reality." (SciShow, The Science of That Dress)Chapter Nine of Herbartian Psychology, "Graphic Hypotheses," begins with something that was first mentioned in Chapter Three:
"It is true that in Reid's comfortable dogmatism we are assured that we perceive the outer world exactly as it is, and therefore we all perceive it alike. But Locke admits that the outer world may be modified in certain aspects,--colour, smell, sound, taste,--but in other more fundamental respects remain unchanged. According to this view, man is the measure of colours, smells, sounds and tastes..."In other words, the size and shape of something may be fairly fixed and common to almost everyone; but on the other aspects, you're on your own. Referring back to his perception games in Chapter Six, Adams says, "Even a simple straight line may mean something slightly different to each new observer, and the greater the number of lines in a drawing, the greater the range within which its interpretation by different observers may vary." However, "when two persons are talking about the drawing that lies before them, there is at least something to go upon, there is a sort of least common denominator of thought, to which all the ideas of each party must be reduced before agreement can be expected." "The fact is that while our mental impressions of a given object are continually changing, they always correspond with each other, and to the given reality."
So there's room for personal interpretation, but there's also the possibility that someone doesn't understand, doesn't have the right information, is just inaccurate. Not everything is relative. The Dress may be seen as white and gold or as blue and black, but nobody has suggested that it's pink and purple, or that it's actually a ski jacket or a pair of boots.
What does this have to do with Herbartianism and education?
First and most practically, teachers can use graphic narrations to evaluate how well students understand something. Hence the value of Charlotte Mason science notebooks. Adams gives the example of student teachers reading Robinson Crusoe, who were asked to make drawings of Crusoe's tent based on the information given in the chapter. The story said that the roof was covered "with flags and large leaves of trees, like a thatch." Apparently some of them took "flags" to mean the Union Jack, and that's what they drew. They weren't stupid, just lacking information.
Second, Adams discusses the non-value of bad or misleading diagrams. If a diagram or an illustration is "an integral part of the idea it illustrates," then it can be worthwhile; otherwise, we might want to reconsider using it. "Milton has been often praised for his reticence in not fully describing Satan. Can we say as much for the illustrators of The Pilgrim's Progress?" "There are certain things that are better left undrawn."
Third, we are given the detailed description of a "Map Robinson Crusoe's Island" contest.The Boy's Own Paper advertised the contest and offered a prize, and Adams says that over a hundred and fifty maps were submitted. The contest contained a couple of possible snags, although those weren't mentioned in the rules. The biggest one is, obviously, that not everything is given in the story, and some things must just be imagined; but the text also contains a few contradictions and impossibilities regarding the geography of the island, so even a careful mapmaker would have to deal with those. You can read more of the details in Herbartian Psychology at the archive.org site, but for now, the educational question becomes the double difficulty "of communicating an idea from one mind to another....The idea must be dissolved, as it were, in words, and then again crystallized out in the new mind....The concrete of one mind must be reduced to its abstract terms, and then rebuilt into the concrete of the new mind." It's like what happens when you beam somebody up on Star Trek.
As a postscript: If the mind is a spider web, Adams says, a teacher may be seen as "a benevolent spider...whose business is not to make plain the already geometrically clear lines of the web, but to see that guiding apperception masses are so arranged that they shall lead ultimately to the centre, by the way, however crooked it may seem, that is best for each seeker." (I'm not sure whether these seekers are supposed to be younger spiders, or what.)
But oh dear, I don't like to be seen as a benevolent spider, do you? I certainly don't feel qualified to decide which way to the centre is "best for each seeker."