Signalled Delay to Reinforcement in Delayed Matching to Sample

Abstract

Five hens were trained on a delayed matching to sample task. The retention intervals started at 0.25 s and were gradually increased until they were 1 s, 2 s, 4 s and 8 s in each session. At the end of training the fifth response to the sample stimulus (red or green square) extinguished the key light and initiated one of the delays which were quasi-randomly selected. At the end of the retention interval the comparison stimuli were presented: a red and a green square. A response to the comparison stimulus that matched the sample stimulus resulted in 3-s access to wheat. An incorrect match resulted in a 3-s blackout. There was then an intertrial interval of 10-s regardless of the trial outcome. Accuracy remained consistently high across all the delays. The percentage of correct responses at the 8-s delay interval remained above 70%. Once behaviour was stable a cue was inserted into the retention interval. The blue key with a cross on it signalled that a correct response would receive reinforcement delayed by 2.5-s. A yellow key with a vertical line on it signalled that a correct response would receive reinforcement immediately. It was hypothesised that signalling a delay to reinforcement would decrease response accuracy on those trials. No differences in response accuracy were found for the different cues indicating that the cue did not affect response behaviour. In the next condition the blue cue now signalled that a correct response would result in 0.5 s access to wheat. The yellow cue now signalled a correct response would be followed by 4.5-s access to wheat. Accuracy for the small and large reinforcer remained the same. Through each condition matching accuracy remained between 60 and 80% regardless of the length of the retention interval. It is thought the gradual increases in retention interval length during training may have been responsible for the maintained high accuracy.