Octopus Consciousness: The Role of Perceptual Richness

Jennifer Mather

doi:10.3390/neurosci2030020

Abstract

It is always difficult to even advance possible dimensions of consciousness, but Birch et al., 2020 have suggested four possible dimensions and this review discusses the first, perceptual richness, with relation to octopuses. They advance acuity, bandwidth, and categorization power as possible components. It is first necessary to realize that sensory richness does not automatically lead to perceptual richness and this capacity may not be accessed by consciousness. Octopuses do not discriminate light wavelength frequency (color) but rather its plane of polarization, a dimension that we do not understand. Their eyes are laterally placed on the head, leading to monocular vision and head movements that give a sequential rather than simultaneous view of items, possibly consciously planned. Details of control of the rich sensorimotor system of the arms, with 3/5 of the neurons of the nervous system, may normally not be accessed to the brain and thus to consciousness. The chromatophore-based skin appearance system is likely open loop, and not available to the octopus’ vision. Conversely, in a laboratory situation that is not ecologically valid for the octopus, learning about shapes and extents of visual figures was extensive and flexible, likely consciously planned. Similarly, octopuses’ local place in and navigation around space can be guided by light polarization plane and visual landmark location and is learned and monitored. The complex array of chemical cues delivered by water and on surfaces does not fit neatly into the components above and has barely been tested but might easily be described as perceptually rich. The octopus’ curiosity and drive to investigate and gain more information may mean that, apart from richness of any stimulus situation, they are consciously driven to seek out more information. This review suggests that cephalopods may not have a similar type of intelligence as the ‘higher’ vertebrates, they may not have similar dimensions or contents of consciousness, but that such a capacity is present nevertheless.

Highlights

Perception can be defined as the reception, organization, interpretation. and experience of incoming information [1]
Sensory systems tend to trade off sensitivity with acuity and high acuity would result in richness of information in terms of sensation
Sensory richness is no guarantee of perceptual richness, complex perceptual ability does not guarantee access to consciousness, but it may be an a priori necessity

Summary

Introduction

Perception can be defined as the reception, organization, interpretation. and experience of incoming information [1]. A third dimension of richness is perceptual, and specifies how sophisticated an animal is in the treatment of the incoming information, what Birch et al [2] call categorization power. There is an important guide for evaluation of perceptual richness in every animal, including octopuses, von Uexcüll’s [5] umwelt or sensory world. It is different for each animal; he says that “there is no real world but as many worlds as species”. The extensive arm brachial cords together make a parallel to the mammalian spinal cord

Vision

Chemical Sensing

Mechanoreception

Conclusions