Sentience ...describes our ability to sense the world around us.... [it is] the foundation on which the mirage of consciousness shimmers. Scientists and philosophers debate whether animals experience consciousness, but most readily ascribe to them the pared-down version of sentience. [loc. 36]
Contrary to received wisdom, humans don't have five senses -- modern cognitive neuroscience suggests that there are more than twenty, possibly as many as thirty-three. Higgins uses a number of examples from non-human animals such as mantis shrimp, star-nosed moles, cheetahs, spiders and octopuses to explore various senses and compare the human and animal sensoria. The mantis shrimp, it turns out, has four times as many colour photoreceptors as the average human, but may actually have 'worse' colour vision: Higgins discusses not only the mantis shrimp (especially an experimental subject named Tyson) but colour-blindness and tetrachromism in humans.
Each of the twelve chapters discusses different sense in the animal and human worlds: 'The Common Vampire Bat and Our Sense of Pleasure and Pain'; 'The Cheetah and Our Sense of Balance'; 'The Common Octopus and Our Sense of Body', and so on. I found the chapters on hearing (the Great Grey Owl, a bird whose wings scatter sound so that its prey can't hear it coming) and the sense of direction (the bar-tailed godwit) most intriguing -- and of course the chapter dealing with the octopus, whose arms can function independently of its brain.
Sentience is packed with case studies and examples, from neurology to zoology (Oliver Sacks is one name that recurs throughout) and discussion of the similarities and differences between human and animal sensoria. Human senses, it turns out, are more flexible and more inclusive than I'd believed. There is some examination of how the perceived world -- the umwelt -- might differ according to the senses available to a particular organism: imagine tasting with your whole body, like a catfish, or hearing the high-pitched sound of your own nervouse system... I found it fascinating, though the Afterword (starting with the duck-billed platypus and concluding that, with technological advances, 'a brave new world of sentience awaits') felt rather slight after the in-depth discussions that preceded it.
Fulfils the ‘glance’ rubric of the Annual Non-Fiction Reading Challenge.
‘Our brains are tuned to detect a shockingly small fraction of the surrounding reality,’ said the neuroscientist David Eagleman. ‘The interesting part is that each organism presumably assumes its umwelt to be the entire objective reality “out there”. [loc. 3805]
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