The effects of changes in consequences on hens' performance in delayed-matching-to-sample tasks

Area of Science:

• Cognitive ethology
• Animal behavior
• Comparative psychology

Background:

• Investigating memory mechanisms in non-human animals is crucial for understanding cognitive evolution.
• The delayed-matching-to-sample (DMTS) task is a standard paradigm for assessing memory in various species.

Purpose of the Study:

• To explore remembering in domestic hens using a delayed-matching-to-sample (DMTS) task.
• To differentiate the effects of delayed reinforcement versus omitted reinforcement on memory performance.
• To assess the utility of response latencies as a metric in DMTS studies.

Main Methods:

• Domestic hens were trained on a mixed-delay DMTS procedure with varying delay intervals (0.25s, 2s, 8s in Experiment 1; 0s, 4s, 16s in Experiment 2).
• Experiment 1 manipulated the delay to reinforcement following correct responses.
• Experiment 2 manipulated both the delay to reinforcement and extinction conditions (no reinforcement for correct responses at specific delays).

Main Results:

• Discrimination performance generally decreased monotonically with increasing delay when reinforcement was consistently available.
• Non-monotonic changes in performance were observed when reinforcement was delayed or omitted, particularly at shorter delays.
• Response latencies increased significantly during extinction conditions, indicating heightened sensitivity to reinforcement availability.

Conclusions:

• Remembering appears to involve a temporal discrimination process in hens.
• The effects of delaying reinforcement and omitting reinforcement on memory are distinct.
• Response latencies offer a valuable supplementary measure in DMTS paradigms for probing memory processes.