Learning efficiency: The influence of cue salience during spatial navigation

In three experiments, male Wistar rats were trained to find a hidden platform in the Morris water maze using two cues for five or ten days. Experiments 1 and 2 investigated two factors of cue salience; proximity to the goal and brightness. Results from Experiment 1 showed that rats tested with a bright distal cue were significantly better at locating the platform than rats tested with the proximal cue after five- and ten-day training with both cues. In Experiment 2, the position of the cues was reversed. Rats tested with a brighter proximal cue outperformed those tested with a distal cue. Findings from Experiments 1 and 2 suggest that brightness acquired more control over rats' behaviour than proximity to the goal. Animals in Experiment 3 were trained with equally bright proximal and distal cues. Unexpectedly, probe tests revealed that rats tested with the farther cue were more accurate than those tested with the proximal cue, but only after extended training. Possible explanations for this result are discussed with reference to errors in directional information estimation and cue assignment, cue elevation and the use of the pool wall as a navigational aid. Taken together, findings point towards the use of an elemental learning strategy involving the more salient of the two cues which emerged earlier when the relative saliences of the cues differed considerably.