Effect of stimulus and response separation in a matching-to-sample task in the brushtail possum (Trichosurus vulpecula)

• Locating stimuli and response manipulanda close together will produce more accurate performance and faster learning in brushtail possums.
• Performance peaked at the current training distance and generalized to distances close to the currently trained distance.
• Performance decreased in accuracy at distances further from the trained level.

This study seeks to investigate the impact of changing the proximity of stimulus and response manipulanda on matching-to-sample performance in possums. Possums were presented with five rows of blue and yellow stimuli arranged vertically 25 mm apart above response levers. Generally, peak performance occurred at the distance from the lever currently being trained. Performance generalized to distances close to the currently trained distance and decreased in accuracy at distances further from the trained level. The findings from this experiment provide evidence for placing stimuli and response manipulanda close together to improve acquisition of a task, and increase the responding accuracy in MTS experiments. This suggests that spatial contiguity in the relative location of stimuli and response manipulanda is critical to animals performing complex operant tasks.