Phenomena¶

Distinctive states and quirks of conscious experience the KB treats as data — what the ontology has to explain. The brief groups four families: illusions, dreams and sleep phenomena, lucid states, psychedelic phenomena. Only the first is seeded so far; the rest get sections as content arrives.

Visual illusions¶

Cases where the visual system delivers a percept that diverges from physical reality in regular, predictable ways. Each is a window onto a specific computation the brain runs by default. Grouped by what the illusion exploits.

Schema

Each row: illusion, origin, what it shows, what it exploits about visual processing. Example images will be added in a later pass.

Geometric / perceptual illusions¶

Illusion	Origin	What it shows	What it exploits
Müller-Lyer illusion (the `>—<` vs `<—>` arrows)	Franz Müller-Lyer, 1889	Two line segments of identical length appear unequal: the one with outward-pointing arrowheads (`<—>`) looks longer than the one with inward-pointing arrowheads (`>—<`).	Almost certainly size-distance scaling — the visual system interprets the inward arrows as a "near corner" and the outward arrows as a "far corner," then unconsciously compensates the apparent size. Cross-cultural variation (less effect in non-rectilinear environments) supports the carpentered-world hypothesis.
Ponzo illusion	Mario Ponzo, 1911	Two identical horizontal bars placed between converging lines (railroad-track perspective): the upper bar — closer to where the lines converge — appears significantly larger.	The same size-distance scaling: converging lines signal depth, the upper bar reads as "further away," the brain enlarges it because a real object that far must be larger to project the same retinal image.
Hering illusion	Ewald Hering, 1861	Two parallel straight lines appear bowed when superimposed on a radial pattern.	Visual cortex's interpretation of radial lines as depth cues — the brain expects parallel lines that recede to converge, so when they don't, it bends them.
[TODO: add Ebbinghaus, Kanizsa triangle, Café-wall, Adelson's checker-shadow as the page grows.]

Ambiguous / multistable figures¶

These flip between two stable interpretations. Direct evidence that perception is constructed, not read off — the same sensory input supports multiple percepts and the brain picks one at a time.

Illusion	Origin	What it shows	What it exploits
Necker cube	Louis Albert Necker, 1832	A wireframe cube ambiguous as to which face is "front" — the percept spontaneously flips between two 3D interpretations.	Bistability in 3D-from-2D inference; the brain commits to one interpretation, then "fatigues" and flips. Direct anchor for predictive-processing accounts of perception as inference.
Rubin's vase	Edgar Rubin, 1915	An image readable as either a vase (white on black) or two facing profiles (black on white) — figure–ground assignment flips.	The figure / ground distinction is itself a constructed inference, not given in the image. Either choice is consistent with the data; the brain has to pick.
Duck-rabbit	Joseph Jastrow, 1899 (popularized by Wittgenstein)	Same image readable as a duck or a rabbit. The two percepts share no visual features in common; only the interpretation differs.	Top-down conceptual influence on perception — what you "see" depends on what category you're priming for. Wittgenstein used it to argue seeing-as is interpretive, not raw.

Impossible figures¶

Geometric configurations that read as 3D objects locally but are globally inconsistent. Demonstrates that local visual processing assembles the percept piecewise without checking global consistency.

Illusion	Origin	What it shows	What it exploits
Penrose triangle	Oscar Reutersvärd (1934, independent); Lionel & Roger Penrose (1958)	A triangle whose three corners each look like valid 3D right angles, but the figure as a whole cannot exist in 3D space.	The visual system stitches the percept together from local cues without enforcing a global consistency check — local feasibility wins over global impossibility.
M. C. Escher's impossible figures (Ascending and Descending, Waterfall, Relativity)	Escher, mid-20thC, often inspired by Penrose	Staircases that always go up, water that flows uphill, gravity that points different ways for different observers in the same scene. Art-grade exploitation of the Penrose-style local-vs-global gap.	Same mechanism as the Penrose triangle, applied at scene scale. Each region is locally coherent; the scene globally can't exist.

Cognitive illusions and biases¶

Systematic, predictable errors in reasoning, judgement, and memory — the cognitive analogue of optical illusions. Two related framings, often used interchangeably (see the cognitive bias vs cognitive illusion distinction):

Cognitive bias — the underlying systematic tendency (the disposition).
Cognitive illusion — the experience of that bias when demonstrated directly (the trigger-revealed instance).

The framing was popularized by Amos Tversky and Daniel Kahneman in the heuristics-and-biases programme (1970s onward); Kahneman's stock comparison was that the visual and the cognitive systems both have illusions. The umbrella has since grown well beyond Kahneman's original list to cover social, motivated, memory, and attention biases.

Heuristics-and-biases (Kahneman / Tversky tradition)¶

The classic perception-analogue cognitive illusions — most have direct lab demonstrations and feel like illusions when encountered.

Illusion / bias	Origin	What it shows	Status
Anchoring effect	Tversky & Kahneman, Judgement under Uncertainty: Heuristics and Biases (Science, 1974)	Numerical estimates are pulled toward an arbitrary number (an anchor) presented first, even when subjects are told the anchor is irrelevant. The classic demo: spin a wheel of fortune, then ask "what percent of African countries are in the UN?" — the wheel result biases the answer.	✅ Robust across many replications and domains.
Framing effect	Tversky & Kahneman, The Framing of Decisions and the Psychology of Choice (Science, 1981)	Equivalent options described as gains vs. losses produce systematically different choices. The Asian-disease problem: identical outcomes, framed in lives saved vs. lives lost, flip the modal preference.	✅ Robust. Foundation of prospect theory.
Availability heuristic	Tversky & Kahneman (1973)	The probability of an event is judged by how easily examples come to mind, not by base rate. Why people overestimate plane-crash and shark-attack risks: vivid examples retrieve easily.	✅ Directionally robust; magnitude varies with task.
Conjunction fallacy ("Linda problem")	Tversky & Kahneman (1983)	Subjects rate "Linda is a bank teller and active in the feminist movement" as more probable than "Linda is a bank teller" — violating basic probability (a conjunction can't be more probable than either conjunct).	✅ Robust, though the interpretation (people misunderstand "probable" vs. people use representativeness as a heuristic) is debated.
Hindsight bias ("I-knew-it-all-along effect")	Baruch Fischhoff (1975)	After learning an outcome, subjects systematically overestimate how predictable it was beforehand. Distorts retrospective evaluation of decisions.	✅ Robust. Direct relevance to introspective reports about one's own past mental states.
Confirmation bias	Documented across many forms; canonical experimental form: Peter Wason, 2-4-6 task (1960)	The tendency to seek, interpret, and remember information in ways that confirm existing beliefs while underweighting disconfirming evidence.	✅ Robust as a family of findings, though "confirmation bias" covers several distinct mechanisms.
Dunning-Kruger effect	Kruger & Dunning, Unskilled and Unaware of It (1999)	Low performers overestimate their ability; high performers slightly underestimate theirs. Often misquoted: the empirical effect is small and partly explained by regression to the mean + measurement error (Nuhfer et al., 2017; Gignac & Zajenkowski, 2020).	⚠️ The effect is real but smaller and more methodological than the popular "stupid people are confident" reading suggests.
Base-rate neglect	Tversky & Kahneman (1973); Bar-Hillel (1980)	When given specific case information and a base rate, subjects ignore the base rate and over-weight the case. Mammogram problems: a positive result on a 90% accurate test for a 1%-prevalence disease still means most positives are false.	✅ Robust; foundational for understanding clinical-decision and forecasting errors.

Cognitive illusions vs. perceptual illusions

A genuine visual illusion (Müller-Lyer) persists even when you know the segments are equal length — perception isn't overridden by belief. Cognitive illusions are different: many of them weaken or vanish when subjects are warned, given training, or shifted to a different format (frequencies vs. probabilities, e.g. Gigerenzer's work). This asymmetry is itself diagnostic: perceptual machinery is encapsulated; cognitive machinery is more permeable to top-down correction.

Errors in how we infer the causes of behaviour — our own and others'. Less perception-illusion-like, more reasoning-tendency.

Bias	Origin	What it shows	Status
Fundamental attribution error	Lee Ross, The Intuitive Psychologist and His Shortcomings (1977); earlier as the correspondence bias (Jones & Harris, 1967)	When explaining others' behaviour, we over-weight dispositional / character causes and under-weight situational ones. When explaining our own behaviour, the asymmetry reverses (the actor-observer asymmetry).	⚠️ The directional effect is real but cross-cultural studies (Choi, Nisbett & Norenzayan, 1999) show it's much weaker in East-Asian populations — partly cultural, not pure cognitive universal.
Just-world hypothesis	Melvin Lerner, The Belief in a Just World (1980)	The tendency to believe the world is fundamentally fair, leading to victim-blaming when bad things happen to people: if X suffered, X must have deserved it (or behaved unwisely). Protective for the believer's sense of safety; corrosive for empathy.	✅ Robust as a tendency; magnitude varies with threat to the believer's worldview.
In-group bias / out-group homogeneity	Henri Tajfel, Social Identity Theory (1970s+)	Members of one's in-group are evaluated more favourably and seen as more individually variable; out-group members are judged less favourably and as more homogeneous ("they all look the same"). Triggers on minimal-group manipulation — even arbitrary group assignment is enough.	✅ Robust; foundation of social-identity research.
Self-serving bias	Documented across many forms (Bradley, 1978; Miller & Ross, 1975)	Successes are attributed to dispositional / self causes; failures to situational / external causes. Protects self-esteem at the cost of accurate self-assessment.	✅ Robust; though magnitude varies with self-esteem and depression status.

Motivated reasoning and belief biases¶

Biases driven not by computational shortcuts but by what the believer wants to be true. Closer to interest than error.

Bias	Origin	What it shows	Status
Motivated reasoning / motivated cognition	Ziva Kunda, The Case for Motivated Reasoning (Psychological Bulletin, 1990)	Reasoning is shaped by the conclusions one is motivated to reach. Subjects spend more cognitive effort scrutinizing evidence that contradicts their preferences and accept supporting evidence at face value. The mechanism behind much of what looks like simple confirmation bias.	✅ Robust as a family.
Cognitive dissonance reduction	Leon Festinger, A Theory of Cognitive Dissonance (1957)	Holding two contradictory beliefs (or acting against one's beliefs) creates an aversive state; the system reduces it by changing one belief, rationalizing the action, or trivializing the inconsistency. Classic demo: the $1 vs $20 study (Festinger & Carlsmith, 1959).	✅ The general phenomenon is robust; specific Festinger-era studies have replication caveats.
Backfire effect ("the corrected misinformation entrenches the belief")	Originally claimed: Nyhan & Reifler, When Corrections Fail (2010)	Hypothesized that corrections sometimes strengthen the original misinformation. Failed to replicate cleanly — Wood & Porter (2019), Nyhan himself in later work has walked back the strong claim. The popular meme that "fact-checking backfires" outran the empirical evidence.	❌ ⚠️ Mostly debunked in its strong form. Don't cite as established.

Memory biases¶

The brain reconstructs memories rather than retrieving them verbatim — and the reconstruction is biased.

Bias	Origin	What it shows	Status
Peak-end rule	Kahneman, Fredrickson, Schreiber & Redelmeier, When More Pain Is Preferred to Less (1993)	Retrospective evaluation of an experience is dominated by its most intense moment (the peak) and its final moment (the end); duration is largely ignored ("duration neglect"). The 60-second cold-pressor study: subjects preferred a longer trial that ended at slightly milder cold over a shorter one ending at peak cold.	✅ Replicated; foundation of Kahneman's experiencing self vs remembering self distinction.
Misinformation effect	Elizabeth Loftus, Reconstruction of Automobile Destruction (1974)	Memory of an event can be altered by post-event information — a question phrased with "smashed" vs "hit" changes recalled speed and even insertion of glass that wasn't there. Anchor for the unreliability of eyewitness testimony.	✅ Robust; legally consequential.
Mandela effect	Term: Fiona Broome (2010, popular usage)	Large groups of people sharing the same false memory of a public fact (Nelson Mandela dying in prison in the 1980s; the Berenstain / Berenstein Bears spelling). Empirically: just confabulation — convergent reconstruction errors driven by similar priors and the dynamics of social memory transmission. The popular framing as evidence of "parallel universes" is unserious; the underlying memory phenomenon is real.	✅ as memory-reconstruction phenomenon; ❌ as parallel-universe evidence.

Statistical-reasoning errors¶

Inferential errors driven by mishandling sampling, base rates, or the structure of the data — closer to faulty methodology than to perception-style illusions, but pervasive in everyday reasoning.

Bias	Origin	What it shows	Status
Selection bias	Statistical concept; long history in epidemiology and survey methodology	Drawing inferences from a non-representative sample. Everyday version: "everyone I know thinks X" — but the people you know aren't a random draw from the population. Research version: studying volunteer samples, internet surveys, or convenience samples without correcting for who self-selects in. The conclusions you reach can be confidently wrong because the sample never gave you access to the question you thought you were answering.	✅ Foundational. Affects almost any reasoning from a self-selected dataset, including most popular journalism.
Survivorship bias	Classic worked example: Abraham Wald's WWII bomber-armor analysis (Statistical Research Group memos, 1943)	A specific kind of selection bias: drawing conclusions from the survivors of a process while ignoring the failures who are no longer visible. Wald's case: the US military wanted to armor returning bombers where they had bullet holes; Wald pointed out armor should go where returning planes had no holes — because planes hit there didn't return. Everyday versions: "successful entrepreneur habits" surveys, mutual-fund track records, "X always works" advice from the people it worked for.	✅ Robust; routinely produces confident wrong conclusions in everyday reasoning.
Gambler's fallacy	Long history; named in modern form by Tversky & Kahneman	Believing that independent random events become "due" — after a string of red on roulette, black is "more likely" next spin. The wheel has no memory; the prior outcomes don't change the probability. Underlies most slot-machine intuitions and "I'm on a streak" reasoning.	✅ Robust. Closely related to apophenia (perceiving structure in randomness).
Hot-hand fallacy / hot-hand effect	Gilovich, Vallone & Tversky, The Hot Hand in Basketball (1985); revisited by Miller & Sanjurjo (2018)	The opposite intuition: that streaks predict continuation. Twist: the original 1985 paper called it a fallacy, but Miller & Sanjurjo (2018) showed Gilovich's analysis itself contained a subtle sampling artifact — the hot hand effect is real in basketball, smaller than fans think but not zero.	⚠️ The "hot hand is a fallacy" claim itself was partly wrong. Cite the 2018 reanalysis.

Term	Origin	What it shows
Cargo cult (as cognitive descriptor, not bias proper)	Anthropological term from post-WWII Melanesia; recast as a thinking pattern by Richard Feynman, Cargo Cult Science commencement address (Caltech, 1974)	A pattern of imitating the form of a successful practice without grasping its function — like the cargo-cult communities who built bamboo airstrips and wooden headphones expecting cargo planes to land, because that's what the wartime US bases looked like. Feynman applied it to pseudoscience that imitates the surface of scientific work (jargon, equations, citations) without doing the underlying work of falsifiable hypothesis testing. The KB uses this framing in the cargo-cult neurochemistry callout for folk-neuroscience phrases that wear lab vocabulary while skipping mechanism. Not a cognitive bias in the Tversky-Kahneman sense; rather, a descriptor for a class of motivated mimicry that often co-occurs with apophenia and motivated reasoning.

Pareidolia and apophenia¶

Cases where the brain perceives structure that isn't there in noisy or random input — and where it does so reliably enough to be diagnostic of how perception works.

Term	Origin	Definition	KB cross-links
Pareidolia	Term: Klaus Conrad, Die beginnende Schizophrenie (1958), borrowing earlier German usage	The tendency to perceive specific meaningful patterns — most often faces — in ambiguous, random, or noisy stimuli. Examples: the Face on Mars (Viking 1, 1976; later Mars Global Surveyor imagery, 1998, showed it was a mesa with light-and-shadow patterns), Jesus on toast, the Man in the Moon, faces in electrical outlets. Strong face-pareidolia is consistent with the visual system's tuned face-detection circuitry (FFA, Kanwisher, 1997) firing on under-determined input.	Activity patterns, the Phenomena layer; future entry on FFA.
Apophenia	Term: Klaus Conrad (same 1958 monograph)	The broader tendency to perceive meaningful connections, patterns, or causation in unrelated events or data. Pareidolia is the perceptual sub-case (patterns in images); apophenia covers all of: seeing conspiracies in coincidences, lucky-streak intuitions in random sequences, "everything happens for a reason" reasoning. The cognitive substrate of conspiracy theories, gambling fallacies, and — in clinical extreme — paranoid delusions.	Pareidolia, Frith's Schizophrenia VSI, Predictive processing (apophenia as over-strong priors / over-weighted predictions).

Why these belong in a KB on consciousness

Pareidolia and apophenia aren't bugs — they are the visible failure mode of the brain's normal pattern- inference machinery. The same circuitry that lets you recognize your friend's face from a glimpse, or notice that the same person keeps appearing at the same coffee shop, is what produces the Face on Mars and the conspiracy theory. A theory of conscious perception that doesn't predict these failures isn't predicting normal perception either.

Pareidolia in art¶

Artists understood the hidden-face / composite-image effect for centuries before psychology named it — these works are direct cultural evidence that pareidolia is reliably triggerable, not idiosyncratic. The KB cites them as applied demonstrations of the underlying perceptual mechanism.

Artist	Period	Representative works	Technique
Giuseppe Arcimboldo	1526–1593, Italian Mannerist	Vertumnus (portrait of Rudolf II, 1590–91); The Four Seasons (1573); The Four Elements	Composite portraits — heads built entirely from fruits, vegetables, books, or fish. The face-detector reads the assembly as a portrait while the inventory reads as a still life simultaneously. Canonical example of weaponized face-pareidolia.
Tobias Stimmer	1539–1584, Swiss Renaissance	Composite "Gorgoneion"-style heads	Composite-head tradition contemporary with Arcimboldo, Northern variant.
Marcus Gheeraerts the Elder	c. 1520–1590, Flemish	Emblem-book illustrations; composite-head and hidden-figure prints	Northern emblem tradition; combines moral allegory with perceptual play.
Matthäus Merian (the Elder)	1593–1650, Swiss-German engraver	Anthropomorphic landscapes — landscape engravings whose hills, trees, and rocks resolve into a face when viewed as a whole	Direct exploitation of the landscape-as-face hidden-image effect — distinct from Arcimboldo's composite portraits in working at scene scale.
Wenzel Hollar	1607–1677, Bohemian etcher	Hidden-figure landscape prints in the Merian / Momper tradition	Continued the anthropomorphic-landscape tradition into the mid-17thC.
Josse de Momper (the Younger)	1564–1635, Flemish	Anthropomorphic landscape series — The Four Seasons as landscape-faces; Spring, Summer, Autumn, Winter	The Northern complement to Arcimboldo: where Arcimboldo built faces from organic objects, Momper built faces from entire landscapes — mountains as foreheads, cliffs as noses, foliage as beards.
Hans Holbein the Younger (adjacent — different mechanism)	1497–1543, German	The Ambassadors (1533) — the floor of the painting contains a stretched, distorted skull readable only from a steep oblique angle	Anamorphosis, not pareidolia. Anamorphosis exploits geometric distortion — the image is recoverable only from a specific viewpoint that undoes the distortion. Related to pareidolia in being a "hidden image" trick, but the perceptual mechanism is different (viewpoint-dependent geometric correction vs. pattern-on-noise inference). Included here for completeness; properly belongs in a future Anamorphosis row alongside Erhard Schön and the broader 16thC anamorphic tradition.

Why these belong in the KB

These works show pareidolia (and anamorphosis) being engineered for, reliably, by trained artists across centuries — strong evidence the underlying perceptual mechanisms are stable enough to design against. They are pre-scientific empirical data points for the pattern- inference machinery the KB's Phenomena layer covers.

Rorschach test¶

Note: not an optical illusion. A projective psychological test — distinct category — that uses pareidolia clinically.

Test	Origin	What it is	Status
Rorschach inkblot test	Hermann Rorschach, Psychodiagnostik (1921)	Ten standardized symmetric inkblots; subjects describe what they see. The clinician scores responses on what is reported, where on the blot, what features (form, colour, movement) drive the response, etc. The premise: under-determined stimuli force projection of internal contents, which is then diagnostic of personality / pathology.	⚠️ Trust with caveats. Reliability and validity of clinical inferences from Rorschach scoring have been heavily contested — Wood, Nezworski, Lilienfeld & Garb, What's Wrong with the Rorschach? (2003) made the canonical critical case. The Comprehensive System (Exner) has weak psychometric support; the newer R-PAS (2011) is better but still contested. Useful in the KB as an anchor for "tests that exploit pareidolia," not as a reliable clinical instrument.

Altered states of consciousness (ASC)¶

The umbrella term for non-ordinary conscious states — those that differ in structure or content from baseline waking awareness. Coined formally by Arnold Ludwig, Altered States of Consciousness (Archives of General Psychiatry, 1966); popularized by Charles Tart's 1969 edited volume of the same name. The Russian equivalent (состояния изменённого сознания, ИСС) tracks the same construct.

The KB cares about ASC for one reason: non-ordinary states are the most informative probes of ordinary consciousness. What shifts (the body schema, the sense of self, the experience of time, the unity of perception) reveals what was being held together in the first place. The ontology has to predict the deformations as well as the default.

Major sub-families — each gets fleshed out as content arrives:

Sleep and dreams¶

Sleep stages and EEG signatures¶

Sleep is not a single state — it's a structured cycle of distinct stages with characteristic oscillations. The standard classification (American Academy of Sleep Medicine, 2007):

Wake — mixed alpha (8–12 Hz) and beta (>13 Hz); desynchronized.
NREM 1 — light sleep, transition; theta (4–8 Hz) predominant; hypnagogic imagery appears here.
NREM 2 — deeper but not deepest; theta background plus two diagnostic transient features: sleep spindles (веретёна сна) and K-complexes.
NREM 3 (slow-wave sleep, SWS) — deepest sleep; dominant delta waves (0.5–4 Hz, large amplitude). Associated with systems-level memory consolidation, synaptic-homeostasis rebalancing, and glymphatic-system metabolic clearance.
REM — desynchronized "wake-like" cortical activity paired with skeletal-muscle atonia; rapid eye movements; vivid dreaming.

Diagnostic NREM oscillations¶

Sleep spindles (веретёна сна) — 0.5–3-second bursts of ~11–16 Hz oscillation, generated by the thalamic reticular nucleus gating thalamocortical communication. Gate sensory input during sleep (you don't wake from a benign noise) and are implicated in memory consolidation. Density correlates with cognitive ability and is reduced in schizophrenia.
K-complexes — single large biphasic waveforms in NREM 2, often paired with spindles. Marker of sleep-protective arousal regulation.
Slow-wave / delta activity — the 0.5–4 Hz dominance of SWS. Builds with prior wake duration (homeostatic Process S in Borbély's two-process model, 1982). Directly tracks "sleep pressure" — the more sleep you've missed, the more delta you generate when you finally sleep.

Phenomenology and content¶

REM dreaming — vivid, narrative, often emotional; hippocampal and limbic activation with prefrontal hypoactivity. Dream content as a window onto memory consolidation and predictive-model maintenance.
NREM mentation — earlier-night, more thought-like, fragmentary. Often forgotten.
Hypnagogic / hypnopompic states (гипногогические / гипнопомпические образы) — transitional states on falling asleep / waking, with characteristic imagery: geometric patterns, faces, fragments of speech, full hallucinatory scenes. Hypnagogic = entering sleep; hypnopompic = exiting. Often confused with dreams but phenomenologically distinct (more passive, less narrative). Useful empirical probe because consciousness is partial in these states — the content is hallucinatory but meta-awareness is often intact.
Sleep paralysis — REM atonia persisting into wakefulness; often accompanied by intruder / pressure / floating hallucinations. Cross-cultural phenomenology with consistent features (the "old hag," the bedroom intruder).

Theories of dream function¶

Activation-synthesis (Hobson & McCarley, 1977) — dreams as the cortex synthesizing a narrative from random brainstem activation in REM.
Threat-simulation theory (Revonsuo, 2000) — dream content preferentially simulates threats; evolved to rehearse threat- response without real-world cost.
Memory consolidation — dreaming as offline replay / reactivation of waking patterns; supports systems-level consolidation. Strong empirical support; possibly the function of REM, with content being less load-bearing.
Predictive-processing / generative-model rehearsal — dreams as the brain's generative model running offline, fine-tuning priors in the absence of sensory input.

Lucid dreaming and meta-awareness during dreams¶

Lucid dreaming — the dreamer becomes aware they are dreaming and can sometimes intentionally direct content. Empirically established via eye-signal verified lucidity (Stephen LaBerge, 1980). EEG/fMRI signatures (Voss et al., 2009) show frontoparietal activation atypical for normal REM — partial reactivation of the meta-cognition machinery.
Direct empirical data point for theories of meta-consciousness: being aware that one is conscious can be present or absent independently of the contents of consciousness.

Hypnosis¶

Hypnotic states — focused attention with heightened suggestibility. Highly variable across individuals (the Stanford Hypnotic Susceptibility Scale identifies stable high-, mid-, and low-suggestibility populations). Active research on whether hypnosis is a distinct state (Hilgard's neodissociation theory) or a sociocognitive phenomenon (Spanos, Lynn). Robust effects: hypnotic analgesia, post- hypnotic suggestion — the mechanism remains contested.

Meditation¶

Focused-attention meditation (mindfulness of breath, samatha) — sustained attention on a chosen object; trains attention-network control.
Open-monitoring meditation (mindfulness, vipassanā) — non-judgemental awareness of all arising contents; correlates with reduced DMN activity in experienced practitioners.
Non-dual states — dissolution of subject–object structure reported by advanced practitioners across traditions; partly overlaps with psychedelic ego dissolution. Neurophenomenology (Varela, 1996) is the methodological framework that takes these reports seriously.

Psychedelic states¶

(Planned deep coverage of specific substances — classic psychedelics, stimulants, opioids, medical stimulants — including biochemistry, history, usage / misusage, and legal status: see task-0002.)

Classic psychedelics (LSD, psilocybin, DMT, mescaline) agonize 5-HT2A receptors primarily on layer-V cortical pyramidal neurons.
Phenomenology: visual / synesthetic distortions, altered time, ego dissolution, dissolution of self–world boundary, mystical-type experience.
Mechanism: entropic-brain hypothesis (Carhart-Harris & Friston, 2014) — disintegration of the DMN and increased entropy of cortical activity; predictive processing reading: relaxed priors at high cortical levels, sensory data rules over expectation.
KB anchors: Shulgin's PiHKAL, Grof's Realms of the Human Unconscious and The Holotropic Mind, serotonin, DMN.

Dissociative states¶

Drug-induced: ketamine, PCP — NMDA-receptor antagonism; characteristic depersonalization, body schema disruption, k-hole experiences. Different phenomenology from classic psychedelics.
Pathological: depersonalization / derealization disorder; dissociative identity disorder; trauma-related dissociation.
Distinct neural correlates from psychedelic states; both classes deform the self-model but along different axes.

Sensory deprivation¶

Isolation-tank / float-tank states (John Lilly, 1950s+) — reduced sensory input → spontaneous hallucinations, altered body schema, time distortion. Direct evidence that the brain's generative model fills in missing input rather than simply going quiet.

Near-death experiences (NDE)¶

Reports of out-of-body experience, life review, tunnel / light imagery, peace, meeting figures. Cross-culturally reported with consistent features but culturally coloured content (van Lommel et al., Lancet, 2001).
Empirical interpretations: cerebral hypoxia + DMT release + cultural priming + REM-intrusion patterns. Empirical literature is small and methodologically constrained; treat NDE claims with caveat.

Flow states¶

Flow (Mihály Csikszentmihalyi, 1975) — full absorption in a skilled task with merging of action and awareness, time distortion, reduced self-monitoring. Whether flow is properly an altered state is contested (some classify it as an optimal-engagement variant of normal waking consciousness).

Cross-cutting note

Several of these states converge on the same handful of structural changes: reduced DMN activity, weakened predictive priors, altered time perception, deformations of the phenomenal self- model (PSM). The fact that very different routes (psychedelic, meditative, dream, NDE) produce overlapping phenomenology is itself evidence about what the default state is holding together.