Disregard. (Must read whole thread before posting . . .)
Electric fields and magnetic fields are the same thing. And electric eels definately can, their electric discharge organs are evolutionarily derived from electric sense organs.
No, they are not.
Homing is a capability rather than a sense. It can depend on several senses, which are multiply redundant - if one sensory cue is absent, others can be used. Birds can use sight (both celestial cues and landmarks), smell, magnetic sense, and their sense of air pressure to navigate.
But do you know what sensing an electric field (not an electric shock) is like? Certainly you have no idea whatever of what a shark or an electric eel percieves when it senses an electric field - this is likely to be as different from anything we sense as sight is from touch.
Why do you suppose that animals can’t perceive qualitative differences in the nature of electric fields or magnetism in addition to just magnitude? It is quite possible that an animal could perceive features of an electric signal that would translate to qualitative differences in the same way that light of different wavelengths differs in color and sound differs in pitch.
Of course one can see something faintly or clearly, and the same with smell. But more importantly, these senses are certainly not “binary,” but have critical qualitative elements. You can see something even if you lack color vision; but color vision adds a lot of additional information. Birds (and most vertebrates) have four color receptors compared to our three, including one for UV, and perceive a range of colors we can no more comprehend than a color-blind person can understand what “red” is.
Certainly the electric and magnetic senses of animals can be counted as ones that we cannot easily comprehend. The pressure senses of fish (in water) and birds (in air) probably qualify as well. While we have rudimentary senses of this nature, they are rather analogous to the ability to be able to tell light from dark compared to true vision with perception of images.
Likewise the sonar senses of bats and dolphins. While these depend on “hearing,” these animals can “visualize” details of their environment in such a way using these senses that makes them fundamentally different than our sense of hearing.
I would assume that there are not only senses we do not have that other animals do, but also that we have sense that we are unaware of. What do you think cause people to “have a feeling” about something? It’s the instinctual part of us that uses tools that we are currently unconsious of. Perhaps, someday, we will evolve to discover new senses that we have. For a guess, I think that we can sense emotions in other people, especially fear. This would correspond to our history, as sensing the fear of others in your tribe would help you escape danger and increase your odds of survival. Remember that the senses we have developed for the purpose of our ability to survive on Earth. I’ve little doubt that there is much going on that we cannot percieve simply because it never threatened or sustained our lives during our evolution.
Now that you explain it, it seems you are probably right about everything you said. It makes sense.
I’m reasonably convinced that my dog’s sense of smell is so much better than mine to be effectively a different sense - like the difference between someone who can see that something is a book and someone who can see well enough to read it. He has smelled a racoon two blocks away through the sewers. (More than once.) He has been able to home in on a slice of pizza at the other end of a baseball field through smell alone. I’m convinced, though I have no firm evidence for, that he can distinguish the scent of many different dogs at popular bushes.
In the spirit of that, how about a sensory perception for altitude unrelated to vision or ears popping.
Another similar idea would be sensing barometric pressure. Isn’t that what animals are sensing when they get fidgety just before a storm?
I once read about an experiment where scientists attached little magnets to homing pigeons’ heads, and it did seem that their sense of direction got screwed up.
Anything in the spectrum of tastes that we can’t taste? Not intensities but flavours?
There are plenty of things that can be sensed that we can’t. Here are a few:
1.) Infrared vision – Pit vipers have crude “pinhole camera” IR vision. They can certainly sense direction and rough shape. The “pits” house IR sensors and give it a (largish) apetrture.
2.) Ultraviolet Vision – Bees , butterflies, and other insects see further into the UV than we do. They basically see flowers as luminous billboards standinmg out against the dul and dark background of chlorophyll-laden leaves and stems.
3.) Polarization vision – although people have a limited capability to sense polarization (look up * Haidinger’s Brush* on the web), it’s nothjing compared to the ability of bees, horeshoe crabs, and other beaastiers that use it for navigating.
4.) magnetic fields – again, people apparently have some slight capability here (I’ve got a book called The Compass in your Nose that talks about this), but other creatures have a considerable ability to sense this, especially microscopic aquatic life that uses the vertical gradient in the field to sense up and down.
5.) electric fields – mentioned above. Used by much aquatic life to sense prey and predators.
6.) “smell” in the water – we really don’t sense smells/tastes as well as aquatic creatures, and they have developed impressive arrys of sensors to take advantage of this.
One can easily imavgine other abilities in other circumstances – creatures capable of receiving and interpreting radio waves, millimeter waves, X-rays, gamma rays, streams of subatomic particles, the ability to discriminate between coherent and incoherent light (using “photon sieves”). Hal Clement, that wonderful hard-SF writer, once wrote a story about creatures on a vacuum planet who were able to “see” using a sort of pinhole ion camera – the mean free path of molecules in the almost perfect vacuum was o long that they traveled in straight lines for meters. Their “nasal” receptors were housed in spherical enclosures with a small aperture at one end, so the emitted moleccules would form a “picture” on the interior of this nasal “eye”. The best description I know of in science fiction of a non-human but perfectly plausible and workable sense.
Good grief.
I kind of noticed it but never thought to question what it was.
I wonder if humans also have some sense of this. Things seem “different” to me before a storm and I don’t think it’s all the stillness and humidity. It’s a slightly “empty” feeling despite it sometimes still seeming hot and muggy.
But what exactly is “fear”?
A sense is a nerve receptor that discharges when it gets a certain physical stimulus. What physical stimulus does “fear” cause?
We “sense fear” by our regular senses…we see someone’s face and movements, we hear their voice, we smell their sweat, we use our brains to infer the person’s internal emotional state by their outward physical state. And we can do this with other animals too, especially if we have learned to read their body language. Pretty much anyone can tell when a dog is scared or when a cat is scared, many people can tell when a horse is scared, we could probably do a pretty good job telling if a monkey is scared. But sometimes we misinterpret those signals, how do you distinguish between fear and aggression, since an aggressive animal is likely to be fearful as well?
The fact is, there is no “fear particle” that can be detected by a nerve cell. Just because a trait would be advantageous to have does not mean an organism will have the trait. So the ability to sense emotions is impossible because emotions are all in your head, they aren’t broadcast into the universe by any mechanism. The only way we can detect emotions is to infer them by observation of the organism experiencing (or not experiencing) the emotion.
Just to add to Lemur’s excellent post, we also use our brains to guess at emotional states by our knowledge of the person’s history and circumstances (They’re in a dark alley and Mike Tyson is getting in their face? Wait, I mysteriously sense fear!).
It occurs to me that there are plenty of ther possible senses that we either have in only rudimentary form, or not at all:
1.) Pressure sense – ability to sense small changes in baromettic pressure on land, or water pressure under water. We have some sense of this, of course, but it’s coarse and uncalibrated. It might be nice to be able to predict thunderstorms, though.
2.) Smell – I mean sensitive smell, sucvh as dogs and cats have, rather than our stifled sense.
3.) More Degrees of Freedom in Color Vision. Even in the range of visible light, we’re not completely discriminating. In our sense of hearing we can clearly distinguish between different pitches. Even people without perfect pitch can tell the difference between two notes. But we can perceive an infinite number of different spectral combinations as the same “green”, because we only have three degrees of freedom in our color sense. We could conceivably have color sense more like a spectrometer, and be able to distinguish between different spectral compositions that now look the same to us. I don’t know how or why this would be accomplishede, but it would be different than the way we see now.
4.) Improved depth perception
We don’t actually have infinitely discriminating hearing, the smallest amount of discrimination would be between hair cells in the cochlea.
So we could imagine a spectroscopic eye that worked the same way. You’d need a prism lens that split the spectrum, then the spectrum would fall on an array of optical sensor nerves. You wouldn’t need them to be as finely sensitive as our cone cells, but due to the prism they’d only activate if light of a known wavelength stimulated them. Pack in enough cells and you’d have a spectroscopic eye, fine enough and you’d be able to see emission and absorbtion lines. Of course, this eye would be useless for seeing images. And Nyarlathotep knows what an organism could actually USE this eye for.
I’m curious about these, “failry,” good responses. I’m guessing, without reading the link, that this means they sucked but you, wanting to be both supportive and polite, didn’t want to point this out.
Which of course is differentiated from the experiment where scientists attached gigantic magnets to the pigeons’ heads and thus impacted their ability to fly. 
Strictly, the question seems to be unanswerable. Any attempts above by analogy to other animals or derived concepts like ‘electricity’ assume that data from our existing sensory modalities when integrated and analysed present a complete “picture” of the phenomenal universe. Which is begging the question.