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

Yang and team worked with three kids with autism.

They taught new tacts—names for pictures—using discrete trial training.

Each child got three conditions: immediate praise and a sticker, or the same reward after random waits of 4–8 s, or 10–14 s.

The team counted how many trials each child needed to master the new words.

Two out of three children learned fastest when the reward came right away.

Even the short 4–8 s variable delays slowed learning.

The longest delays of 10–14 s slowed it even more.

One child learned at the same speed no matter the delay.

Majdalany et al. (2016) ran almost the same study eight years earlier.

They used fixed 6-s and 12-s delays and got the same result: immediate beats delayed.

Xue et al. (2024) extends that work by showing variable delays hurt too.

Barnard et al. (1977) showed the same pattern in pigeons—response rates crashed after 4 s.

Davis et al. (1972) found the same drop in rats.

Across species and tasks, the rule stays: the sooner the reinforcer, the faster the learning.

Bottjer et al. (1979) looks like a contradiction—they used a 15-s delay to help kids talk.

But that delay was a prompt, not a barrier.

They waited 15 s to give the child a chance to speak first, then delivered the reinforcer.

So the papers don’t clash; they just use delays for different jobs.

If you run tact programs, give the chip, praise, or token the moment the child labels the item.

Even small, unpredictable waits can add days to mastery.

Check your timing with a stopwatch—aim for under one second.