Conditional same-different categorisation in the short-
beaked echidna
Darren Burke
Fiona Russell
CISAB
Why Echidnas?• Phylogeny
– Monotremes –separate evolutionary path from all other mammals for 120-200 million years
– Mixture of reptilian and mammalian features, considered ‘primitive’
• Interesting Neurophysiology– Large relative brain size– Very large cortex for body size– Unusual cortical organisation– Unusual sensory systems: Electro-receptors
• Adaptable and successful– Doing something right!
Why categorisation?• Interested in having some measure of their
ability to perform a relatively complex cognitive task
• Needed something that didn’t rely on social sensitivity or high visual acuity – or even sophisticated high-level visual categorisation
• Knew echidnas could do visual discriminations (Buchmann & Rhodes, 1978; Gates, 1978)
• Chose conditional same/different categorisation as a measure of their ability to acquire an “abstract” “concept”
General methods• Two choice y-maze• Food dishes covered to prevent use of
olfactory cues (piloted this previously)• stimuli varied to prevent use of low-level
perceptual cues • side of correct stimulus determined by
Gellerman schedule• Rewarded every correct choice• Removed from apparatus between trials
General methods• Two choice y-maze• Food dishes covered to prevent use of
olfactory cues (piloted this previously)• stimuli varied to prevent use of low-level
perceptual cues • side of correct stimulus determined by
Gellerman schedule• Rewarded every correct choice• Removed from apparatus between trials
Exp 1: Basic discrimination
• Provide easy trials to teach basic discrimination
• used correction trials
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Number of correct trials/10
S+ S-
Before board After board
Exp 2: shape discrimination
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Number of correct trials/10
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S-
Exp3: Conditional shape discrimination
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Number of correct trials
S+ S-
S- S+End of correction trials
Exp 4: Same/different categorisation
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Number of correct trials
Transfer stimuli
Training stimuli
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- Transfer stimuli interspersed with training stimuli in test phase (20%)
Exp 5c: conditional same-different discrimination
• Testing for quite complex categorisation
• combining two previously demonstrated abilities – same/different categorisation – conditional discrimination
• First attempt was unsuccessful (Experiment 5a) – Had trouble learning conditionality
• so then separately successfully trained other half of conditional discrimination– different rewarded if black on white
(Experiment 5b)
Training stimuli
Transfer stimuli
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Exp 5c: results
○ = old stimuli
▲ = novel stimuli0
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Sessions
Number of correct trials
All Stimuli
0.00
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0.60
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Sessions
Percentage of correct responses
Conclusions• Pitpa successfully performed a conditional same/different
discrimination– A quite complex cognitive feat
• Whether this is a consequence of echidnas possessing a cognitive sophistication to match their neural complexity or of the particular pattern of training she received is a question for future research – With more subjects!