This much from Wikipedia (for convenience):
The knowledge argument (also known as Mary’s room or Mary the super-scientist) is a philosophical thought experiment proposed by Frank Jackson in his article “Epiphenomenal Qualia” (1982) and extended in “What Mary Didn’t Know” (1986). The experiment describes Mary, a scientist who exists in a black and white world where she has extensive access to physical descriptions of color, but no actual human perceptual experience of color. The central question of the thought experiment is whether Mary will gain new knowledge when she goes outside the black and white world and experiences seeing in color.
The thought experiment was originally proposed by Frank Jackson as follows:
Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like “red”, “blue”, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence “The sky is blue”. … What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not?
In other words, Jackson’s Mary is a scientist who knows everything there is to know about the science of color, but has never experienced color. The question that Jackson raises is: once she experiences color, does she learn anything new? Jackson claims that she does.
I too would argue that it does. Let’s consider a variation on the thought experiment, and then return to its original version:
Mary is a brilliant scientist studying swimming, forced to investigate the world of swimming in an enclosed room that has a spigot for drinking water, but no sink, bathtub, or any way of creating a body of water however small. Mary, nevertheless, studies the physical properties of water extensively, as well as the physiology of swimming. Indeed, she becomes a world expert on those two subjects. If Mary is given the opportunity to leave the room and step into a pool, will she learn something about swimming?
Of course she will, because she will experience being in water through many of her senses, and not just second hand in her imagination from reading only. She’ll be able to experience the feel of water, its coldness, and wetness, and the smell and taste the chlorine, and hear the water lapping against the sides of the pool. She’ll experience water through all of her senses, something she has never done before.
The original thought experiment is a bit misleading because Mary is using vision both to read, and to perceive color.
Let’s consider reading: Mary looks at a page and on the most basic level sees arrangements of black and white. (Consider if she’s looking at a printed page of Sanskrit or some language she doesn’t know.) Meanwhile, Mary has learned to read — a long and arduous learning process — enabling her to translate arrangements of black and white on a page into semantic meaning. Indeed, I’d say most folks who read are no longer conscious of the colors (foreground and background) that make up a printed readable page (in languages they can read).
So for Mary there are two modes going on. One is reading, which requires color, but color per se is not relevant (as long as the foreground and background colors are sufficiently different). The other mode is experience of color per se.
By definition, different neural pathways are involved in seeing ‘yellow’ vs. ‘purple’ (otherwise we couldn’t distinguish them). Therefore, when Mary sees colors besides black and white for the first time, new neural pathways will be activated.
I suppose one could argue that ‘activating new neural pathways’ and ‘knowledge’ are two different things. Maybe. But let’s also remember that ALL human knowledge of the physical world originates as a ‘new neural experience’ in some experimenter’s mind. That’s what scientific observation and empiricism is! We have the benefit of summaries and abstractions and distillations of experimenters like Galileo and Madame Curie — whose theories rest on other experimenters being able to confirm and repeat the same neural pathway experiences (observations) by replicating decisive experiments.