Krasis

1One claim, six cases

In 1960, in a report to the US National Association of Educational Broadcasters, McLuhan stated his central hypothesis plainly: “It is the ratio among our senses which is violently disturbed by media technology.” He meant it as a claim about the nervous system. He grounded it in the stress physiology of Hans Selye. His critics, from Jonathan Miller to Irwin Bross, read it the same way and attacked it as bad neurology. When the neurology McLuhan later attached to it, a theory of left and right brain hemispheres, failed, the claim was quietly reclassified as metaphor. It was less refuted as physiology than set aside.

This series has argued that the claim can be recovered, and that modern neuroscience, especially work on how the brain weights and combines its senses, can state it precisely. The first paper, Sensory Syncrasis, made that historical and theoretical case. The papers that followed applied the framework to six cases.

Each paper stands alone. Read together, they make a single argument: that McLuhan's sense ratio is a real, measurable configuration; that people start from different settings of it; that media and chemistry re-temper it; and that the changes matter most precisely because the people inside them cannot easily see them. This synthesis sets out that argument as a whole.

2The framework: syncrasis and its five dimensions

McLuhan's word was "ratio." It is the right starting point and the wrong ending. Research on how the brain combines the senses shows that one part of the configuration is a true ratio: when two senses are combined, the weights given to each trade off against one another, in proportion to how reliable each is (Ernst & Banks, 2002)3. But the configuration has other parts that a ratio cannot describe.

The series therefore uses a broader term, sensory syncrasis, from Greek synkrasis, "a mixing together, tempering," the root of idiosyncrasy. A person's syncrasis is, literally, the idiosyncrasy of their senses. It has five dimensions:

1. 1Sense ratio: the relative weight each sense receives when they are combined. This is McLuhan's own term, kept for the part that is truly proportional.
2. 2Overall gain: how strongly all channels are amplified at once, set by arousal and the brain's neuromodulators.
3. 3Integration mode: whether signals from different senses are fused into one experience or kept apart.
4. 4Inside–outside balance: how attention is shared between signals from the body and signals from the world.
5. 5Persistence: how long a setting lasts after its cause is gone.

In the vocabulary of predictive processing, all five are aspects of how the brain assigns confidence, or precision, to its signals. The series uses that vocabulary to describe mechanisms but keeps it out of its names, so that the framework does not depend on any single theory of the brain.

The framework is a proposal. No study has measured all five dimensions in any population. What the series does is assemble evidence gathered for other purposes and read it through these coordinates, grading where the reading is firm and where it is interpretation.

3The family of terms

The series coins one term for the framework and one for each case. All share the root krasis, except typomora and its partner epanaphony, which name a delay and a voice rather than a mixture. The table gathers them.

The family works as a vocabulary, not only a set of labels. Each term names a relation to the same configuration: where it starts (heterocrasis), what holds it in place (typomora), where it moves (exocrasis), what alters it (pharmakrasis), what fixes it (narcocrasis), and what loosens it again (anacrasis). Collision checks found no prior academic use of most terms, though Syncrasis is also the name of an insect genus; exact-phrase searches in the scholarly databases are still to be run.

4Where a configuration starts, and what re-tempers it

Starting points

No one meets a medium from a neutral position. Heterocrasis asked whether ADHD is a systematically different starting configuration, and found partial support. The clearest difference is in overall gain: a nervous system in which weak signals struggle against noise, so that background noise helps people with ADHD slightly while hindering others (Nigg and colleagues, 2024)4, and choices run noisier while learning stays intact (Hauser and colleagues, 2014). Integration is not looser, bodily self-perception is unclear, and inner speech is present but loosely coupled to action. The broader lesson is that a starting configuration shapes what every later medium does.

Media

Two papers dealt with the computing environment. Typomora focused on the input layer. For about fifty years, people put language into networked machines almost entirely by keyboard, a production habit inherited from literacy, because speech recognition and bandwidth could not yet carry voice. Literacy itself measurably reconfigures the brain (Dehaene and colleagues, 2010)5, so a typographic habit is a physiological configuration, not just a cultural one. As those technical limits fell around 2016 to 2022, the interface began returning to voice. Comprehension is largely the same whether people read or listen (Deniz and colleagues, 2019), so what changes is how language is produced, timed and checked, not what is understood.

Exocrasis dealt with the rest of the environment. People remember less of what they photograph and let a device keep (Henkel, 2014)6, and habitual GPS users show weaker spatial memory over time (Dahmani & Bohbot, 2020). Reading on screens is slightly shallower for expository text, a gap that grew over two decades (Delgado and colleagues, 2018). Action games strengthen exactly the skills screens demand (Bediou and colleagues, 2018). And whole-environment studies, of Facebook's rollout and of paid deactivation, find small but real effects on well-being.

Chemistry

Pharmakrasis treated drugs as the clearest case of what McLuhan said media do, because they change the configuration within minutes and can be studied in controlled trials. Cannabis speeds the felt passage of time; psilocybin disrupts timing of longer intervals; ketamine loosens the sense of owning one's body; LSD deepens the emotional response to music; sedatives turn sensory responses down. When a drug meets a medium, the result is a hybrid in McLuhan's sense. The best-documented case is psychedelic therapy with music, where the quality of the music experience predicts outcomes (Kaelen and colleagues, 2018)7.

Narcocrasis followed one drug configuration to its extreme. In dependence-type addiction, the allostatic model describes a persistent shift in the brain's hedonic set point and a recruited anti-reward state (Koob & Le Moal, 2001)8. The drug stays vivid. What becomes invisible is the shifted baseline: the medium, with the drug as its content. McLuhan and Koob turn out to descend from the same physiological tradition, through Selye and the concept of allostasis.

Re-tempering

The same paper described two routes back. One turns reward gain down, as GLP-1 drugs and naltrexone appear to do. The other makes the ground briefly visible, as psychedelics may, acting as what McLuhan called an anti-environment. Recovery itself, anacrasis, appears to depend heavily on other people: rats choose social contact over heroin and crave less afterwards (Venniro and colleagues, 2018)9, and psychedelics in mice reopen a window specifically for learning from social reward (Nardou and colleagues, 2023).

5What runs through every case

Read side by side, the six cases share five patterns. None of them belongs to one paper; each appears wherever the framework is applied.

The ground changes, and it is hard to see

In every case, what changes is the background condition of perception rather than any single thing perceived. The typed era became the unnoticed way language was made. The screen sets a reading pace readers follow without choosing it. In addiction, the shifted baseline is felt as "how the world is," not as a state. McLuhan's claim that media effects are invisible because they become environments holds across all of them. That is also why they are hard to study: brief lab exposures measure the figure, and the ground has to be measured over time and across whole environments. The findings that failed replication in this area mostly measured the figure.

Every extension is also an amputation

No case shows pure gain or pure loss. Action games sharpen visual timing while slow reading goes unpractised. GPS extends navigation while the inner map fades. A drug restores a baseline it has itself shifted. Saving information frees memory for the next thing while letting the saved thing go. McLuhan's pairing of extension and amputation is not a figure of speech here. It is the most consistent empirical pattern across the series.

Small per person, large in aggregate, and persistent

The measured effects are modest, typically a tenth to a third of a standard deviation, and well-being associations with technology are at most a fraction of a percent of variance. But they apply to entire populations, daily, for years, and they accumulate: GPS-related decline over three years, reduced social media use persisting after incentives end, a hedonic baseline that outlasts the drug. Across the series, persistence appears to be the decisive dimension. It is what turns a small shift into an environment.

Gain is the best-measured dimension

Of the five dimensions, overall gain has the strongest evidence in almost every case: the noise benefit and noisier choice in ADHD, sedatives turning sensory responses down (less firmly), raised reward thresholds in addiction, and a lower-effort default for reading on screens. Integration mode and the inside–outside balance are where the evidence is thinnest. That unevenness is itself a finding: it shows where the next generation of measurement is needed.

The routes back run through other people

The most unexpected pattern concerns recovery and regulation. Rats choose social contact over drugs and crave less afterwards. Psychedelics reopen a window for learning from social reward. Thinking aloud to a listener who responds reverses Vygotsky's path from social speech to inner speech, returning thought to its social form. Inner speech in ADHD is present but loosely coupled, and an external listener may supply some of the coupling. Across very different evidence, the configuration seems to re-temper best in company. The ancient meaning of anakrasis, mixing with others, turns out to describe it.

6What the series does not claim

A synthesis is where overreach is most tempting. The limits are worth stating together.

It does not claim media cause harm. Every case shows change with specific costs and specific gains. The series asks what an environment tunes people toward, not whether it is good or bad.

It does not claim technological determinism. Each case ties change to conditions that could have been otherwise: bandwidth limits that lifted, settings a drug is taken in, social contact that changes recovery. Configurations can be re-tempered, and much of the series is about how.

It does not claim dramatic individual effects. The measured effects are small per person. The claim concerns their scale, persistence and invisibility.

It does not claim the five dimensions are established measurements. They are a proposed framework. No study has measured all five in any population, and several cells in every table rest on interpretation rather than direct evidence. Integration mode and the inside–outside balance are the least measured.

It does not claim certainty about mechanism. Predictive processing supplies the clearest vocabulary for the five dimensions, but the series keeps its terms independent of that theory, so that the framework would survive if another account of the brain proved better.

It does not offer clinical advice. Several papers discuss drugs, addiction and ADHD. They describe research. They are not recommendations for anyone's treatment or use of any substance.

It does not rest on every source being settled. Each paper lists references still to be confirmed, and some McLuhan quotations depend on secondary reproductions. Those checks are part of the work still to be done.

7Conclusion: McLuhan for an age of measurement

McLuhan worked by probes, not proofs. He threw out claims to see what they revealed, and he was often loose with evidence. That method made him famous and made him easy to dismiss. When his one attempt to anchor the sense ratio in neurology failed, there was nothing to hold the claim up, and it drifted into metaphor.

What has changed since is the measurement. Neuroscience can now describe how the brain weights its senses, how arousal sets the gain on all of them, how body and world compete for attention, and how settings persist. Economics can now change whole media environments and measure the result. Pharmacology can alter the configuration in a controlled trial. None of this existed in usable form when McLuhan was writing. Together, it lets his central claim be described and examined in a way he never could.

The series has tried to put the two together: to keep McLuhan's structure and replace his authorities. The result is a framework, sensory syncrasis, and a family of terms that name what happens to it: where it starts, what holds it, where it moves, what alters it, what fixes it, and what loosens it again. Much of the framework is still interpretation, and the series has tried to say so wherever it is.

The practical upshot is the one McLuhan himself drew. If the most important effects of a medium are the ones we cannot see, the first task is to make them visible. "There is absolutely no inevitability," he wrote, “as long as there is a willingness to contemplate what is happening.” Each paper in this series is an attempt at that contemplation, using tools McLuhan did not have: to turn some part of the ground back into figure, long enough to see it, and perhaps to re-temper it.

The papers in the series

References

Core references used in this synthesis. Each paper carries its own full list.

1. 1McLuhan (1960), Report on Project in Understanding New Media, National Association of Educational Broadcasters
2. 2McLuhan & Fiore (1967), The Medium Is the Massage ("no inevitability" quotation)
3. 3Ernst & Banks (2002), Nature 415: 429–433
4. 4Nigg et al. (2024), JAACAP 63(8): 778–788; Hauser et al. (2014), JAMA Psychiatry 71(10): 1165–1173
5. 5Dehaene et al. (2010), Science 330: 1359–1364; Deniz et al. (2019), Journal of Neuroscience 39: 7722–7736
6. 6Henkel (2014); Dahmani & Bohbot (2020); Delgado et al. (2018); Bediou et al. (2018)
7. 7Kaelen et al. (2018), Psychopharmacology 235(2): 505–519
8. 8Koob & Le Moal (2001), Neuropsychopharmacology 24: 97–129
9. 9Venniro et al. (2018), Nature Neuroscience 21: 1520–1529; Nardou et al. (2023), Nature 618: 790–798