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Escape and avoidance learning in the earthworm Eisenia hortensis
W Jeffrey Wilson1, Nicole C Ferrara1, Amanda L Blaker1
1Department of Psychological Science & Neuroscience Program , Albion College , Albion, MI , USA.
Peerj
|February 6, 2014
Summary
Earthworms can learn to escape aversive stimuli through instrumental learning. In as few as 12 trials, earthworms adjusted their behavior to control an aversive light, demonstrating learning capabilities.
Area of Science:
- Animal behavior
- Neuroscience
- Learning and memory
Background:
- Early research in 1912 suggested earthworms could learn spatial discrimination.
- Later studies in the 1970s proposed this observed behavior was likely chemotaxis, not true learning.
- This study investigates a different form of instrumental learning in earthworms.
Purpose of the Study:
- To examine earthworms' ability to learn to escape and avoid an aversive stimulus.
- To determine if earthworms can exhibit instrumental learning beyond simple chemotaxis.
- To assess the speed at which this learning occurs.
Main Methods:
- Utilized a T-maze setup with an aversive white light stimulus.
- Experimental group ('master' worms) could terminate the light by increasing movement.
- Control group ('yoked' worms) had their behavior independent of the light stimulus.
Main Results:
- Master worms demonstrated a significant change in behavior within 12 trials.
- The behavior of master worms came under the control of the light-contingent escape contingency.
- Yoked controls did not show similar behavioral changes, isolating the learning effect.
Conclusions:
- Earthworms are capable of instrumental learning, specifically escape and avoidance learning.
- This learning can be acquired rapidly, within a small number of trials.
- The findings challenge previous notions and support a more complex understanding of earthworm cognition.
