Changes in progressive-ratio performance under increased pressures of air.
Air pressure alone can move a progressive-ratio break point, so watch environmental variables when thinning reinforcement schedules.
01Research in Context
What this study did
Researchers put rats in a chamber where the air pressure was cranked up. The rats had to press a lever for food, but each new food pellet cost more presses than the last. This is called a progressive-ratio schedule.
The team wanted to know if high pressure air would change the 'break point' — the spot where rats quit pressing.
What they found
Sometimes the rats pressed to a higher ratio before they stopped. Other times they quit earlier. The outcome depended on how big the ratio jumps were and what gas filled the chamber.
Nitrogen pressure had the biggest effect. More nitrogen usually pushed the break point up or down.
How this fits with other research
Keesey et al. (1968) first showed that progressive-ratio schedules give clean, straight lines when you plot brain-stimulation dose against work output. Thomas (1974) keeps the same schedule but swaps brain wires for air-pressure tanks, proving the tool works for environmental as well as electrical reinforcers.
Iannaccone et al. (2021) took the same progressive idea into a human therapy room. Instead of lever presses under pressure, kids with autism faced progressive delays before earning tokens. Their break point was contextually appropriate behavior. All three studies trace one core idea: keep making the response 'cost' more and watch where the client stops.
Kuch (1974), published the same year, also used rat lever presses but shaped how long the rat held the lever down. That paper shows reinforcement boundaries can sculpt response form; Thomas (1974) shows they can also shift response quantity when an outside variable — air pressure — enters the mix.
Why it matters
If you run progressive-ratio or progressive-delay programs, remember that outside conditions can quietly raise or lower the client's quitting point. A stuffy room, noisy hallway, or even medication side effects might act like the nitrogen in the rat study. Check the environment whenever you see an unexpected break point. A quick fix — quieter setting, shorter ratio steps, or a different reinforcer — can put the learner back on track.
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02At a glance
03Original abstract
Rats performed on progressive-ratio schedules that required an increasing number of responses for each successive reinforcement. The number of responses required increased until the subjects failed to complete the next ratio in the sequence within 15 min. Response-ratio increments of two responses, five responses, and 20 responses were investigated. The size of the final completed ratio generally increased with increases in the progressive-ratio step size. Increased pressures of air in a hyperbaric chamber led to both increases and decreases in terminal ratio size, with the differential effects depending on both air pressure and on the size of the progressive-ratio increment. Changes in the number of responses in the final ratio were related to increased pressures of nitrogen, as similar pressures of helium produced few effects.
Journal of the experimental analysis of behavior, 1974 · doi:10.1901/jeab.1974.21-553