Nice post, JD. Imo, they have more in common than not.
One thing that irritates me is when horror is lumped in with fantasy and science fiction. It makes as much sense as lumping comedy in with mystery or romance. Horror doesn't necessarily have anything to do with magic or speculative themes like future technology or contact with aliens. Saw is 'realistic' horror, Nightmare on elm street is fantasy-horror, Invasion of the Body Snatchers is science fiction-horror.
Well, that "lumping in" is because the three genres (or sub-genres of fantastic fiction, to be more accurate) are all closely related historically and literarily. Granted, you do have the realistic (or, more properly, naturalistic) horror of things like
Saw (or, to use a literary example, much of Guy de Maupasssant's horror work, though that is by far
much,
much more subtle and effective), but they do come from much the same source. And, if one must be pedantic about this, "horror" -- at least in the broader sense of fantastic fiction or verse whose intent was to stir feelings of dread, unease, fear, terror, and the like -- was by far the earliest and most venerable of the three, dating back as it does to the earliest forms of storytelling. And, as Groff Conklin showed very well with his anthology
Science Fiction Terror Tales, both sf and fantasy owe a great debt to the horror genre.
To take a slight divagation... it rather saddens me when I see the terror tale spoken of in such a disparaging fashion (at least, so I read your comment above; I may be misinterpreting here), as it is as broad and subtle a field as any, from the wistful eeriness of Oliver Onions' "The Beckoning Fair One" or the poignant terror of W. H. Hodgson's "The Voice in the Night" to the comically grotesque (yet no less chilling) "A Visitor from Down Under" or "The Traveling Grave" of L. P. Hartley, or the poetic grandeur and terror of much of Théophile Gautier's work, or the visions of the sublime and terrible of the best of the Gothic novelists and short story writers.
As for horror not having anything to do with "magic or speculative themes like future technology or contact with aliens"... even your own examples call that into question. A great deal of Fritz Leiber's work was based on precisely that connection, while Chad Oliver's "Let Me Live in a House" (a.k.a. "A Friend to Man") is very much about an encounter with aliens; Brunner's novel
The Sheep Look Up (called one of the 100 best horror novels of all time) is speculation about future trends technologically and otherwise... and so on.
Teresa: very good post. As Faulkner put it in his Nobel acceptance speech:
the problems of the human heart in conflict with itself [...] alone can make good writing because only that is worth writing about, worth the agony and the sweat
While I agree with this sentiment, I do not think (as is obvious from my posts elsewhere) that this need be the primary reason for writing a tale; there may be many others. But it
is what drives great literature.
Which, incidentally, brings up the contention that sf is "technological". This is a common misperception, but a misperception nonetheless. Plenty of science fiction has little or nothing to do with technology, from Lester del Rey's "Day Is Done" (1939) to (again) "Flowers for Algernon" (1958; pub. 1959) to the bulk of Ballard's work (or, for that matter, Aldiss'
Report on Probability A (1968)-- sorry, Chris, but it really is a good example, no?) to Lovecraft's "The Colour Out of Space" (1927) to Theodore Sturgeon's
More Than Human (1953)... or even Robert A. Heinlein's
Stranger in a Strange Land (1961). There are numerous other examples here, too. At most, with exceptions such as the work of George O. Smith, sf is about the effects of technology on society; and often even that is rather elliptically approached in favor of wider concerns.