Octopus Consciousness: The Role of Perceptual Richness

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.

Cephalopod Behavior: From Neural Plasticity to Consciousness

“…Perhaps the most intriguing aspect is their almost complete lack of stereotyped behaviors or fixed action patterns. Indeed, the development of well-oriented flexible responses to changes in stimuli or environmental contexts to mention some (e.g., Sanders and Young, 1940 ; Maldonado, 1963b , 1965 ; Messenger, 1973 ; Sanders, 1975 ; Darmaillacq et al, 2004 ; Agin et al, 2006 ; Marini et al, 2017 ; Hanlon and Messenger, 2018 ) suggests that cephalopods employ domain specificity - as recently proposed by Birch et al ( 2020 ) and overviewed by Mather ( 2021a , b ) -, a faculty strongly associated with active brain processing (Hirschfeld and Gelman, 1994 ) and, as we will further mention in this paper, a theory of mind (ToM), i.e., the ability to intuit the thoughts and beliefs of others by a sort of ‘mind reading' faculty that requires some neural encoding of social domains (e.g., Frith and Frith, 2006 ; Apperly, 2011 ; for cephalopods see Godfrey-Smith, 2013 ).…”

“…Of course, as noted above, this varies according to the sensory systems with which each species is endowed (e.g., chemical-tactile, visual, and auditory). Cephalopods appear to possess a large p-richness in chemo-tactile and visual discrimination (review in: Marini et al, 2017 ; Mather, 2021b ) and are able to retain episodic-like memories (e.g., Pronk et al, 2010 ; Jozet-Alves et al, 2013 ).…”

“…In this synthesis, the five dimensions are: perceptual richness (p-richness), evaluative richness (e-richness), integration both at a given time (unity) and across time (temporality), and self-awareness (e.g., selfhood). Notably, a discussion around p-richness in octopus has recently been initiated by Mather ( 2021b ). Table 1 lays out a possible correspondences between these five dimensions and the criteria specified by Seth et al ( 2005 ).…”

“…We highlight the strengths, drawbacks, and lacunae when considering these animals as candidates for a distinct level or degree of consciousness. The topic has been covered previously in a series of papers (Mather, 2008 , 2021a , b ; Edelman and Seth, 2009 ; Birch et al, 2020 ; Feinberg and Mallatt, 2020 ). We will highlight the essential aspects of these works.…”

The Case for Octopus Consciousness: Unity

“…Researchers have given us a lot of information about the use of vision in octopuses, less in terms of mechanoreceptive and chemical cues [56], but few studies about the combination of cues from more than one modality even though people and animals live in a multimodal world. Because the octopus moves out from its sheltering 'home' and conducts saltatory (stop-and-go) search in the nearby areas [57], it must be using a combination of visual information from the eyes [58] and chemotactile cues to the arms [59] to find prey.…”