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The second process: why it stops hitting

By the Myo team

Tolerance isn't your brain running low. It's a second, slower process that grows stronger every time you repeat the first one, a model Solomon and Corbit worked out in 1974.

You know the shape of it even if you've never named it. The first time was extraordinary. The tenth time was fine. The fiftieth time you did it anyway, felt almost nothing, and then felt slightly worse than before you started.

Most people read that as depletion: the tank runs low, the good chemical runs out. That reading is intuitive, popular, and wrong. The actual explanation is stranger and more useful, and it was worked out in 1974.

Two processes, not one

Richard Solomon and John Corbit proposed that every affectively charged experience sets off two processes rather than one (Solomon & Corbit 1974).

The first, the a-process, is fast. It tracks the stimulus closely: it arrives when the stimulus arrives and fades when it goes. This is the hit.

The second, the b-process, is slow. It starts late, builds gradually and is slow to decay. It opposes the first in direction and outlasts it. When the stimulus ends, the fast process stops but the slow one is still running. What's left is the comedown.

What you feel at any moment is the difference between the two. Solomon called this the state rule: when a outweighs b you are in State A, and when b outweighs a you are in State B, the after-reaction of the opposite sign (Solomon 1980). For a new experience that gives a fast peak, a sag, a steady level, then a drop through baseline into the opposite feeling and a slow drift back.

The asymmetry that changes everything

If that were all, nothing would change over time. But repetition treats the two processes differently, and this is the whole insight. The fast process stays roughly stable. The slow opposing process gets stronger, starts sooner, and lasts longer. Solomon's model puts it in exactly those terms: b-processes are strengthened by use and weakened by disuse.

Same stimulus, but the felt result keeps shifting, because one term keeps growing. Less high, more comedown. Eventually there is barely any high, and the comedown is the main event. That's tolerance: a second process that learned, rather than a tank that emptied.

The evidence it was built on

The famous curves were drawn from a handful of striking patterns.

In work Solomon reviews, dogs in a harness received a 10-second shock to the hind feet. Heart rate shot up, peaked about five seconds in, and began to fall while the shock was still on. When it stopped, heart rate dropped below baseline before creeping back. A "veteran" dog that had received hundreds of shocks over many days showed almost no rise at onset and a much deeper, longer drop afterwards. The after-reaction had become the larger event.

Then parachutists. On first jumps, military parachutists showed terror in free fall and a few minutes of stunned relief after landing. After many jumps the fear was usually gone. They reported a thrill during the fall and an exhilaration afterwards that could last two to three hours.

Ducklings show the direction that matters for most habits: a positive hit with an aversive opponent. Imprinted ducklings make distress calls when the "mother" object is taken away, and with repeated one-minute exposures and removals, the calling after each removal grew.

The most useful single result is about spacing. In a duckling experiment by Starr, reported in Solomon (1980), four small groups each got exactly six minutes with the imprinting object in total. Only the gaps between short exposures differed. With one-minute gaps, distress calling grew until it filled about three quarters of the observation time. With two-minute gaps it grew less. With five-minute gaps it did not grow at all. Same total exposure, very different b-process.

This is animal work in small groups plus field observation, with feelings inferred from heart rate or distress calls. A model built from patterns, not a measured feeling.

Tolerance and withdrawal are one mechanism

Solomon listed three things that tend to appear when a strong stimulus is repeated: contrast (the opposite feeling right after), habituation or tolerance (the hit shrinks), and a withdrawal syndrome (the after-reaction becomes long and intense).

In the opponent-process view these are one thing seen from two sides. A stronger b-process subtracts more during the stimulus, which you experience as tolerance, and outlasts it for longer, which you experience as withdrawal. The comedown is the tolerance, showing up after the stimulus has gone.

From Solomon to allostasis

Neuroscience took the idea further. Koob & Le Moal (1997) described addiction as a spiral in which counter-adaptation produces a negative state that drives further use. In Koob & Le Moal (2001) this became the allostasis model: with heavy, repeated drug use, the opposing processes don't fully return to their normal range between doses, so the reward set point itself shifts.

Their later review (Koob & Le Moal 2008) names the "antireward" side: reduced dopamine and opioid function in reward circuits, plus recruitment of brain stress systems. It comes from drug research, mostly in animals, and nobody has shown that a phone produces it. What carries over to everyday habits is the shape of the idea, not the chemistry. For the set-point question itself, see what a dopamine baseline is.

Where the theory is weak

Opponent-process theory is a model, and it has real limits. The first is that the b-process was described, not found. Solomon inferred it from curves, and there is no single neural process anyone can point to as "b". The allostasis work offers candidates, but they are drug-specific. The theory is also flexible enough to be hard to refute: almost any after-effect can be read as a b-process after the fact.

Learning matters more than Solomon allowed. He argued conditioning was neither necessary nor sufficient for addictive motives. Shepard Siegel's work pushed back: in rats, morphine tolerance turned out to be partly a learned response tied to the setting where the drug was given (Siegel 1975), and drug-related cues affected whether a heroin dose was fatal (Siegel et al. 1982). On this account, much of the opposing reaction is triggered by cues in advance. Your bed, the bus stop and the sofa may be cues as well as places.

It doesn't explain craving on its own. Robinson & Berridge (1993) argued that repeated use can sensitize wanting itself, so craving can grow even with no withdrawal to escape. Wanting vs liking covers that account.

And none of the classic studies involved feeds, so applying it to scrolling is a reasonable analogy, not a tested result.

Why this reframes "cutting back"

Under the depletion model, the intervention is obvious: stop consuming, let the tank refill. That's the logic of a dopamine detox, and it doesn't survive contact with the literature. Under the opponent-process model there's no tank. There's a learned second process, and learned things decay on their own schedule: slowly, unevenly, and in proportion to how thoroughly they were trained. Three consequences follow.

The comedown is the part that grows. People log the reward. The opponent process is what accumulates, and almost nobody logs it, because it shows up later, attached to nothing obvious. The dull hour after a feed is a good example (why everything feels boring after scrolling).

Spacing trains the second process. In the duckling data, short gaps built the opponent and long gaps didn't, with the same total exposure. Many small, closely spaced hits can train it more than a few spread-out ones, which is why the habit that feels trivial is often the expensive one.

Stopping abruptly also makes the imbalance loud. Remove the fast process and the slow one plays alone for a while. That's not proof you were addicted, and it's not proof that quitting works. You subtracted one term. It's also part of why short breaks feel worst at the start and why their gains often fade afterwards (why 30-day challenges fail).

What it means for a normal day

You can use the theory without believing every part of it, and four readings follow from it.

  1. Space the quick hits. If gaps let the opponent decay, the number of checks matters more than the minutes. Three planned sessions a day train less than thirty reflexive ones. The practical guide to stopping doomscrolling has setup changes that make spacing easy.
  2. Treat the after-reaction as information. When you feel flat an hour after something, look at what came before it. Over a week, the pattern usually points at one or two frequent, effortless rewards.
  3. Expect the first days of cutting back to feel worse. That's the b-process running without its partner, and it fades with disuse. Judge a change after weeks.
  4. Change the cues as well as the habit. If part of the opposing reaction is learned, moving where and when you do something weakens it faster than willpower in the same setting.

How Myo uses this

Opponent-process theory is one of the mechanisms Myo's model is built on, and the science page cites Solomon & Corbit as the source. In the model, each reward you log adds a fast peak and feeds a slower opposing term that grows with frequency and decays more slowly than the peak. That's why a day of many small, effortless rewards can come out worse than its pleasures suggest. The coefficients are Myo's modelling choices, not measured constants. Myo models from what you log and does not measure dopamine; what a self-check can and can't tell you explains why no app can.

FAQ

What is opponent-process theory in simple terms?

It's the idea that any strong feeling triggers a slower opposite feeling that outlasts it. A pleasure is followed by a dip, a fright by relief. With repetition the first feeling stays about the same while the opposite one grows stronger and longer, so the overall experience shifts from mostly high to mostly after-effect. Richard Solomon and John Corbit proposed it in 1974 to explain tolerance, withdrawal and how new motives form.

What are the a-process and the b-process?

The a-process is the immediate reaction to a stimulus: fast, tied closely to the stimulus, and fairly stable over time. The b-process is the opposing reaction it sets off: slow to start, slow to build and slow to fade. What you feel is the difference between them. In Solomon's model the b-process is strengthened by use and weakened by disuse, which is why repetition changes how something feels even when the stimulus doesn't change.

Is tolerance the same as running out of dopamine?

Not in this theory. Opponent-process theory explains tolerance as an opposing process that has grown stronger, not as a supply that has run low. The later allostasis model does describe reduced reward-system function in addiction, but that comes from drug research and involves a shifted set point and recruited stress systems, not an empty reservoir. For everyday habits, the useful picture is a learned counter-reaction that fades with time and spacing.

Does opponent-process theory apply to social media?

Possibly, but nobody has tested it directly. The classic evidence comes from dogs, ducklings, parachutists and drugs, not feeds. The pattern people describe with scrolling, a small lift followed by a longer flat stretch that grows with frequent use, fits the theory's shape. Treat it as a useful lens rather than a proven mechanism. Other accounts, such as the unpredictable reward schedule of feeds, explain part of the pull too.

Is opponent-process theory still accepted?

As a description of how feelings change with repetition, it is still widely taught, and it shaped modern addiction models such as allostasis. As a complete explanation, it has known gaps. The b-process was inferred rather than identified, the theory can explain almost any after-effect after the fact, and later work showed that learning and environmental cues shape tolerance more than Solomon allowed. It is best seen as one useful model among several.

Sources

Myo models dopaminergic state from behavior; it does not measure dopamine. Not medical advice.

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