Women at peak fertility (~10 days prior to their period) are judged more beautiful - proved by stripper income as well as lab results.

Briefly glimpsed people excite us as though the uncertainty will all pan out in the direction of more beauty (encouraging further investigation) - this also works for briefly flashed photos.

Pale skin shows imperfections better, so allows for better judgment of health (if so, then the above "glimpse" effect would make darker skinned people initially seem more exciting). I always believed this preference to be learned, not innate.

Women with a .67-.8 waist:hip ratio are most exciting to men (given a fixed overall slenderness).

Dissimilar genes ("MHC" - "histocompatability") are identified by scent (by their chemical effects and not directly, I presume) in mice, and lead to sexual preference (presumably because dissimilarity in those genes is important to avoid inbreeding-type recessive defects). Similar receptors exist in humans, and sweaty t-shirts are preferred with increasingly dissimilar MHC.

Women prefer the sweaty t-shirts of more physically masculine men when fertile; otherwise they don't care as much or can't detect it as well.

Women tolerate feminine-looking men (e.g. soft, youthful face) relatively more when they're less fertile.

Women's menstrual cycles may change after smelling another woman's sweat.

Activating vasopressin receptors in the brain causes pair-bonding;polygamous species can be made monogamous and vice versa by manipulating the receptors for vasopressin, or its prevalence. For human males, there's already a genetic test (in the area known to code for vasopressin receptors) that predicts infidelity and partners' dissatisfaction (did they measure vasopressin response directly?)

Foxes pair-bond for a single breeding season (the male stays long enough to help raise the kits).

From David Eagleman's book

Sound and vision are integrated at a low level. Double-beep with single-flash is perceived as double-flash.

What gets sent to higher-level processing are differences between expected input and actual input (number of connections sending info from higher-level part to lower-level vision is greater than low->high). Also e.g. you can't tickle yourself. [perhaps this anticipation helps learning precisely timed hand-eye (more generally: motor-sensory) moves as in sports, music, and dance]. Further, decisions, movements, and inputs are shifted (after learning) so that causally-connected inputs+decisions are perceived as happening at the same time (they're not; different senses have different lags). e.g. if a button->flash mechanism has a 1/10 sec delay, you'll adjust and feel that the light comes on at the same time as you push the button; remove the delay, and then on your next push you think the light came before the push.

More visually-salient events (a larger/brighter/moving square) are perceived as longer duration.

Implicit learning: e.g. unconscious (visual) learning: experts at sexing day old chickens, or spotting German vs. British planes in WWII, are clueless to describe the features they use. But after weeks of teaching by example (student gets the same view, guesses yes/no, is corrected by expert) most people can learn.

People who can't recall any new memories learn the skill of Tetris exactly as well as normal people; their dreams are also filled with falling blocks, although they won't remember that they came from a game they were playing.

Liking those who are like you: if Rasputin shares your birthday, you describe him in more favorable terms. If something or someone has a similar name, you like them more. Weird. Presumably there's some innate same-physical-type (obviously including race, maybe sex) respect or liking as well. First-letter match of name matters for profession, mate, etc. and first-sound or first-few-letters is even stronger.

Priming/exposure: even though you don't remember seeing something recently, you're more likely to recall it (e.g. look at your word choices). If you've seen a face before, you'll find it more attractive than if it's new (stranger danger?) If you've heard a claim before (even if you judged it dubious or false the first time), you're more likely to think it's true the second time (possibly part of you remembers that it's familiar and that's weak evidence for its validity; this seems reasonable to me, and of course that vote can be overwhelmed if you remember specific strong reasons against it).

Association: standard advertising tricks.

Hunches: shuffled decks of cards with win/lose (money) outcomes; you know some are more favorable than others. You'll take 25 draws before you'll say which decks are good, but you have sweaty hands drawing from a bad deck by the 13th draw.

Soliciting hunch-feelings: if you're not self-aware, flip a coin to decide. If, seeing the result, you think letting the coin decide is stupid, your hunch was for the opposite. If you go along with the coin, then you had no strong hunch to the contrary. That's why telling someone "flip a coin to decide" after they've reached an impasse is useful advice (if they don't follow it perfectly).

Brains of experts are faster and more energy efficient (in their expert skill, of course) than people who are worse. We can speculate that they were spending more energy while learning (and consciously coaching themselves, or listening to coaching). People who learned Tetris well exhibited this pattern (eventually: electrically quiet brain; skill burned into [low-level?] efficient brain circuits). This is why experts can sometimes choke under pressure; they start interfering by trying to consciously control what's become implicit.