The effect of brief delays to reinforcement on the acquisition of tacts in children with autism

Three boys with autism, came to a university clinic.

Each child had one-to-one discrete-trial tact sessions.

The teacher showed a picture, gave the prompt "What is this?", and delivered praise plus a tiny toy.

Some trials the toy came right away. Other trials it came after 6 seconds or 12 seconds.

An alternating-treatments design flipped the delay every ten trials so the team could see which speed built new labels fastest.

Two kids learned the new picture labels fastest when the toy arrived right after the answer.

The same two kids needed more trials when the reward waited 6 or 12 seconds.

One child showed no clear difference across the three delays, but the trend still favored immediate reinforcement.

Xue et al. (2024) ran almost the same study but swapped the fixed 6-s and 12-s waits for variable waits of 4-8 s and 10-14 s.

Their results matched: any delay, fixed or variable, slowed tact learning. Because Yang added the variable condition, their paper slightly updates the 2016 finding.

Bottjer et al. (1979) looked at 15-second delays too, yet they used the wait as a prompt to get kids to speak. Their delay helped, while Majdalany’s delay hurt. The difference is purpose: one study used the pause to cue talking; the other used it after the answer was already right, so the pause only stalled reinforcement.

Davis et al. (1972) showed the same slow-down in rats: longer signaled gaps between bar press and food dropped response rates. The animal lab backs the kid lab—delays weaken behavior.

If you run tact programs, deliver the reinforcer the moment the child answers correctly. Keep tokens, stickers, or praise within arm’s reach. Even six seconds can cost you extra trials and extend therapy time. Quick delivery is a no-cost way to speed up language gains.