Auditory discrimination: role of time and intensity in the precedence effect.

The team worked with rats in a small lab arena. They played two clicks from different speakers. One click came first, then a second click echoed after a tiny delay.

The rats had to poke the speaker that made the first click. The scientists changed two things: how long the delay lasted and how much softer the echo was. They tested delays from 0.04 to 8 milliseconds and echo drops from 1 to 10 decibels.

Rats almost always picked the first click if the echo came 0.04–8 ms later. When the echo was more than 5 dB softer, the rats were right almost every time.

Putting both tricks together—short delay plus softer echo—pushed correct choices above 95 percent. Timing and intensity each helped, but together they gave rock-solid stimulus control.

Badia et al. (1972) showed that differential reinforcement alone can teach rats to pick the correct speaker in just one or two sessions. V et al. (1979) now show that you can get the same spot-on choices without extra rewards, as long as the echo is timed and softened just right.

Raslear (1981) later found that louder tones make rats respond more even when rewards stay equal. This backs up the 1979 idea that intensity itself can steer behavior.

Hayes et al. (1975) got peak shift with response-independent reinforcement, proving auditory control can emerge without tight reward schedules. V et al. add the rule book for echo cues that make the control almost perfect.

If you run auditory discrimination tasks, tweak echo delay and volume before you add extra reinforcement. A 5 dB drop and a sub-8 ms delay can lock in stimulus control with little training. Try it next time you set up speaker pairs for localization or conditional discrimination.