Differential responding as a function of auditory stimulus intensity without differential reinforcement.

Researchers played tones at different volumes while rats pressed a lever for food. The schedule stayed the same every time. No extra food was given for pressing during loud or soft sounds.

The rats first heard only a few volumes or many volumes. Then the team watched how fast the rats pressed at each loudness level.

Louder tones made the rats press faster. Softer tones slowed them down. The link was clearest in rats that started with only a few volumes.

Stimulus intensity alone, without any change in payoff, can push response rate up or down.

Stancliffe et al. (2007) later showed the same pattern in mice. Higher force on the lever sped up presses that met the force rule. Together the two studies say, 'Make the physical job easier and behavior speeds up across species.'

Anonymous (1995) and Lowe et al. (1995) looked at the flip side. When the lever needed more force, rats pressed less. That seems opposite to S et al., but the key difference is what was changed. S et al. changed the sound in the room; the later papers changed the work needed on the lever. Both follow the same rule: more effort or less stimulation slows responding.

Zentall et al. (1975) showed that any sound tied to a press can keep the behavior alive, even if food is free. S et al. adds that the loudness of that sound also tunes the speed of the behavior.

When you set up a task, notice the built-in sensory load. A quiet tablet click may slow a client’s rate compared with a louder click. If you want faster responding, first check that the stimulus is easy to notice and the response is easy to do. Small tweaks in volume or force can give you free gains before you ever change the reinforcement plan.