Transitive inference in cleaner wrasses (Labroides dimidiatus).

Area of Science:

• Comparative cognition
• Animal behavior
• Neuroethology

Background:

• Transitive inference (TI) is crucial for decision-making, involving inferring unknown relationships from known ones.
• While demonstrated in mammals, birds, and insects, TI capabilities in fish, particularly in non-social contexts, remain largely unexplored.
• Cleaner wrasses (Labroides dimidiatus) exhibit complex social interactions, suggesting potential for advanced cognitive skills.

Purpose of the Study:

• To investigate the capacity for transitive inference in cleaner wrasses (Labroides dimidiatus).
• To determine if cleaner fish can pass a transitive inference task, extending cognitive research to this species.
• To explore the potential benefits of TI for cleaner fish, given their complex social decision-making.

Main Methods:

• A transitive inference task was designed using visual stimuli and a 5-term series (A-B+, B-C+, C-D+, D-E+).
• Four cleaner wrasses were trained on premise pairs, with positive and negative reinforcement indicating reward or non-reward.
• Performance was assessed by presenting a novel, non-adjacent pair (BD test) to evaluate inferred relationships.

Main Results:

• Cleaner wrasses successfully passed the transitive inference task, choosing the predicted outcome (D) over the other option (B) in the novel BD test.
• The fish's choices were consistent with transitive inference, indicating they inferred the relationship between B and D.
• Reinforcement history alone did not predict the observed choices, supporting a genuine inferential process.

Conclusions:

• Cleaner wrasses exhibit transitive inference capabilities, comparable to those observed in mammals and birds.
• This study provides evidence for advanced cognitive abilities in fish, challenging previous assumptions about their intellectual capacity.
• The findings contribute to a broader understanding of cognitive evolution and the diversity of problem-solving strategies across taxa.