Sentience in cephalopod molluscs: an updated assessment

Area of Science:

• Marine biology
• Neuroscience
• Animal ethics

Background:

• Cephalopods, including octopus, cuttlefish, squid, and nautilus, are marine molluscs with complex nervous systems.
• Assessing sentience—the capacity for subjective experience and feelings—in non-human animals is a growing area of scientific and ethical concern.
• Previous research has explored indicators of sentience in various animal groups, necessitating updated reviews.

Purpose of the Study:

• To systematically evaluate the evidence for sentience in four major groups of cephalopods.
• To apply a consistent framework of eight criteria assessing both neural and behavioral indicators of sentience.
• To identify knowledge gaps and inform ethical considerations for cephalopod welfare.

Main Methods:

• Utilized a framework of eight criteria to assess evidence for sentience.
• Reviewed existing scientific literature on cephalopod nervous systems and behavior.
• Assessed confidence levels (very high, high, unknown) for each criterion across different cephalopod taxa.
• Updated and expanded upon previous reviews of cephalopod sentience.

Main Results:

• Octopuses and cuttlefish demonstrate strong evidence of sentience, meeting six of eight criteria with very high or high confidence.
• Squid show substantial evidence of sentience, meeting five of eight criteria with very high or high confidence.
• Evidence for sentience in nautiluses remains largely unknown due to limited research, meeting only one criterion with high confidence.

Conclusions:

• Octopuses and cuttlefish are highly likely to be sentient, warranting ethical consideration.
• While squid show significant evidence, further research is needed for conclusive assessment.
• Nautilus sentience is currently undetermined, underscoring a critical need for dedicated research to inform welfare practices.
• The lack of evidence for criterion failure, rather than evidence of failure, suggests that insufficient research is the primary limitation.