New Limitation: Unihemispheric Sleep

[Phil Masters]

This subject came up in a thread on the Transhuman Space board recently, and after reading up on it, I realised that there was scope for game simulation.

Unihemispheric Sleep

-50%

This limitation can be applied to the Doesn't Sleep or Less Sleep advantages, or to the Sleepy disadvantage. What it means is that the time spent not sleeping thanks to the former, or the extra time that would be spent sleeping thanks to the latter, is instead spent with half your brain asleep, and the other half more or less fully functional.

While you are in this state, you have -2 to IQ and DX, and -1 to Per, and the same penalties to all skills based on those attributes. You also gain the Hidebound disadvantage (unless you already have it), and One Eye. (If you already have One Eye, you become fully blind for half the time you are in this state.) You can move around freely, hiking, swimming, or flying; if a situation arises needing rapid or complex decision-making or creativity, you can come fully awake, but this is the same as waking up from normal sleep.

You can take both Doesn't Sleep or Less Sleep and Sleepy so long as you put this limitation on both. In that case, you sleep properly little or not at all, but spend much of your time with only half a brain running while the other half recovers.

This is primarily a racial feature; for a start, most cetacean templates should probably include Doesn't Sleep with this limitation. It might also be genetically engineered into some templates for "warrior" parahumans, while in some settings, elves are described as going into "trance states" instead of sleeping; this limitation can provide a mechanism to simulate that with a veneer of quasi-scientific rationalisation. However, research suggests that normal humans have a very limited capacity for unihemispheric sleep. This is generally below the level of resolution of the GURPS rules (it mostly explains why some people sleep badly in strange beds), but it could justify buying this limitation for highly vigilant (or hypervigilant) cinematic heroes who literally sleep with one eye open.

[(E)]

While more simplistic I wrote it up as a combination of doesn't sleep and something like split personality. Personality A being the right brain, B being the left brain and C being the fully awake state. The reasoning being half the brain is better at some tasks than the other half.

[Bruno]

I've actually wondered about a perk "Sleeps with eyes open" - in humans this is pretty much always part of a sleep-wake state disorder, and unlike unihemispheric sleep you really are properly asleep. The game effect would be that you can be woken by visual stimulus as much as by sound, touch, or to a limited extent smell (for humans).

In realistic humans this should usually be associated with something like Sleepwalking, Light Sleeper, Nightmares (representing either actual nightmares or just generally bad sleep), etc. In cinematic humans this is associated with Combat Reflexes, the Deep Sleeper perk, Patients of Job perk, and Intimidation bonuses.

[Flyndaran]

I had a cat that sometimes slept with her eyes open. Quite creepy. She also loved sleeping for hours at a time with me at night. So what's normal for one species like humans may be a sign of a sleep disorder in another.

And some sleepwalking humans show unusual levels of alertness not typical of the shambling zombie cliche. I held entire conversations while asleep with people that never realized that I was not awake. I often have trouble falling asleep like far too many, but never had problems staying asleep. I lived above a mechanic's shop, so Light Sleeper is thankfully one problem I don't have.

[whswhs]

At least in humans, I believe the left half of the left eye's visual field and the left half of the right eye's visual field both connect to the right hemisphere, and conversely for the right halves. If I've got that right, then having one hemisphere asleep wouldn't exactly give you one eye; it would be less loss of depth perception than restricted vision.

[Bruno]

I sleep with a blindfold because my eyes don't always stay closed when I'm asleep; particularly around the hour or two before I wake up. I usually don't wake up fully, but it's very disorienting to be asleep and seeing stuff at the same time. The next step of brain malfunction is full hypnopompic paralysis, which I get a good dose of every now and then :P

Chronic hypnogogic/hypnopompic paralysis would be a good use of repurposing Nightmares; for the unprepared it's pretty nightmarish anyways.

[Phil Masters]

Originally Posted by whswhs

At least in humans, I believe the left half of the left eye's visual field and the left half of the right eye's visual field both connect to the right hemisphere, and conversely for the right halves. If I've got that right, then having one hemisphere asleep wouldn't exactly give you one eye; it would be less loss of depth perception than restricted vision.

Having looked at the Wikipedia entry on the topic, I was thinking of that picture there of a bird with, literally, one eye open and one shut. But that effect seems to be common but not universal in animals undergoing unihemispheric sleep.

I guess that the phenomenon could lead to all sorts of side-effects, depending on precise mechanisms and brain structures. Realistically, it seems to correlate with a small or absent corpus callosum (the structure which links the two halves of the brain), presumably so that the waking half doesn't keep pestering the sleeping half, so any creature capable of the trick might have to have a significantly non-human-like brain and mind - and defining effects for a playable character is an exercise in hypotheticals. But imposing reduced attributes and 20-40 points in assorted disads for "half your brain is currently OoS" feels about right, one way or another.

[Varyon]

Originally Posted by Phil Masters

While you are in this state, you have -2 to IQ and DX, and -1 to Per, and the same penalties to all skills based on those attributes. You also gain the Hidebound disadvantage (unless you already have it), and One Eye. (If you already have One Eye, you become fully blind for half the time you are in this state.) You can move around freely, hiking, swimming, or flying; if a situation arises needing rapid or complex decision-making or creativity, you can come fully awake, but this is the same as waking up from normal sleep.

This looks to be a good case for Temporary Disadvantage. That's -20% for the IQ penalty (-10%/level, doesn't affect Will or Per), -30% for the DX penalty (-15%/level, doesn't affect Basic Speed*). I'm going to assume the note of skills is redundant, and that you don't intend to double the penalties when using skills. Hidebound adds -5%, while One Eye would add -15%. Presumably, Blindness would instead be -35%, and you shouldn't be able to take both One Eye and Blindness (so you use the difference in cost). I'm not certain what would be an appropriate trait for Bill's suggestion, but it seems like a lesser version of Bad Sight (Low Resolution, P:ES12) might work. That's [-25] for -4 to Vision and -8 for fine detail; [-5] for -1/-2 might work, for -5%. This puts the Limitation at -60% (Bad Sight), -70% (One Eye), or -90% (Blindness).

*A full -1 to Basic Speed - but not Basic Move - would also make sense, for a further -15%. That boosts it to -75%, -85%, or -105%.