“Survival behaviours thus have very old roots that make them universal. But the kinds of experiences humans call conscious feelings-that is emotions-I propose are a much more recent development, possibly emerging via evolutionary changes in the human brain a mere few million years ago” (Le Doux ‘A Brief History of Ourselves’ p.4 )

In Jablonka and Ginsburg’s[1] recent book ‘The Evolution of the Sensitive Soul’, they argued that once animals developed an ability called ‘Unlimited Associative learning’ as a by-product they would acquire sentience. Their fascinating and detailed story attempted to discover how sentience evolved and traced it back 550 million years ago to the Cambrian Explosion. While the story they told involved detailed scientific analysis it also had a dramatic feel. In the world of the Cambrian explosion you not only had the most complex predator/prey interaction in the history of the world up to that point; but according to Jablonka, creatures of the Cambrian explosion were creatures whose lives involved constant anxiety. These creatures were the first creatures to have feelings about the world they inhabited; however, they had not developed systems that helped them manage these feelings. So, they lived in a state of constant fear. Jablonka goes as far as to imply that such creatures lived in an emotional paranoid state that was a-kin to psychosis:

“The Cambrian probably witnessed the first nervous breakdowns: the first Cambrian subjectively feeling animals would have been nervous wrecks, with the equivalents of paranoia and posttraumatic stress disorder (PSTD) Dominating their mental lives (‘The Evolution of The Sensitive Soul p. 430)

 

Jablonka’s grim but dramatic story portrays the Cambrian Explosion as a kind of subjective nightmare for its inhabitants.

The story she tells in one that has interest for the philosophy of mind, biology, neuroscience etc. Another area where her story of the evolution of consciousness will have importance is in the subject matter of psychiatry. When scientists try to understand human suffering, and mental pathologies, they partially rely on models derived from the study of other mammals.  The assumption is that such mammals because they have similar brain structures as humans; provide reliable but fallible ways of understanding the neuroscience of human suffering. Scientific studies of mammals in various different threatening situations indicate that they behave in ways that are similar to the way humans behave (the fight or flight response), and that their brain states when they engage in fear behaviour, are similar to our brain states when we engage in fear behaviour. In all mammals the walnut area at the centre of the brain (The Amygdala) plays a key causal role for in their fear behaviour. For this reason when psychiatrists and psychologists are trying to understand psychological disorders such as anxiety disorders, or phobias they heavily rely on animal models.

The reason that we rely heavily on animals when trying to understand human behaviour is that it is easier to study animals directly than it is to study humans. There are obvious ethical constraints on doing invasive experiments on humans. When it comes to studying other animals, millage varies on the degree to which we can study them invasively. Humans are typically reticent when it comes to studies on animals who they have emotional attachments to; such as fellow primates e.g. Chimps, or Dogs.  Such reticence will be tempered when experiments seem likely to cure diseases that plague humanity such as cancer or various neurological disorders. But unless there seems to be a direct practical benefit in doing invasive experiments most humans would deem it an unjustified practice[2]. Hence the majority of invasive research on animals is performed on animals who humans have a less close attachment to; Rats are a paradigm experimental animal. As mammals they have brains which are structured similarly to our own and Rats don’t typically trigger our empathy; hence they are the go to animal neuroscientists study when trying to understand the neuroscientific nature of our subjective experiences.

Studies of Rats indicates that not only do they have brain areas structured similarly to our own but they also have behavioural patterns similar to ours. Jaak Panksepp has argued based on behavioural and neuroscientific evidence that all mammals share with humans seven basic emotional systems: (1) Fear, (2) Panic/Grief, (3) Seeking (4) Lust, (5) Care (6) Play (7) Rage. There is little debate with Panksepp’s characterisation of the similarly structured brain states and behavioural patterns in all mammals. The issue is with whether all mammals actually subjectively experience fear when they engage in fear behaviour. For Higher Order Theorists of Consciousness like Joe Le Doux there isn’t sufficient evidence for us to attribute conscious states to non-human mammals as they lack certain cortical features that Le Doux deems necessary for a state to be conscious.  In his book ‘Anxious’ Le Doux argues that the ineffective nature of contemporary neuro-pharmacological treatments for mental illness stem from the fact that theorists think that the drugs are attacking conscious feelings; when in fact the drugs are merely attacking behavioural responses (a rat freezing) that may not be accompanied by subjective states of any kind.

Given that the debate as to whether all mammals have subjective experiences has a practical bearing on subjects such as neuropharmacology; Jablonka’s argument that subjective experience predates mammals by millions of years isn’t just a theoretical but a very practical question.

 

 

Ginsburg and Jablonka’s Evidence

“Using these criteria, we identify four new transitions in the evolution of neural animals: the transition from multiple exploratory and directed reflexes to limited associative learning; the transition  from limited associative learning to UAL and minimal consciousness;  the transition from imagination to symbolic representation and communication” ( ‘The Evolution of the Sensitive Soul’ p. 343)  

Like Le Doux, Jablonka focuses on the evolution of movement and on creatures who have the capacity to move towards nutrients and away from danger. Even simple Bacteria have this capacity. Jablonka agrees with Le Doux such simple creatures probably do not have sentience.  Jablonka’s story diverges from Le Doux’s story in that she argues that with the evolution of Unlimited Associative Learning creatures develop consciousness, whereas Le Doux argues that higher cortical areas are the magical sauce that creates consciousness.  However, before discussing Unlimited Associative Learning, I first need to outline the nature of its simpler ancestor Limited Associative Learning.

Limited Associative Learning: Skinnerian Organisms

The evolution of Limited Associative Learning[3] provided a massive advantage for creatures who had it. The advantage it provided can be seen in the amount of living creatures today who still use it as a form of learning. Jablonka notes that as well as fish, amphibians, reptiles, birds, and mammals, even invertebrate groups including nematodes, Platyhelminthes, crustaceans, chordates, arthropods, annelids and molluscs display LAL (ibid p. 294).  She also notes that all animals that demonstrate evidence of limited associative learning are bilateral, have brains, and probably evolved in the Cambrian era (ibid p. 293).

In order to understand LAL one must first understand how it relates to conditioning. Since Pavlov discovered classical conditioning and Thorndike and Skinner discovered operant conditioning there has been much debate on how they relate to each other. The primary question that people have wanted to resolve is which is more fundamental; classical or operant conditioning? The consensus; backed more by tradition than evidence, is that classical conditioning is the fundamental form of conditioning and operant conditioning was derived from classical conditioning.

Jablonka, parses classical conditioning as a type of perceptual learning, and operant conditioning as a kind of world learning. In classical conditioning a particular stimulus (food being presented), causes an unconditioned response (salivating). By pairing the food stimulus constantly with a neutral stimulus (a bell ringing) the animal eventually develops a conditioned response of salivating when the bell rings. In this experimental setting the animal is being passively conditioned to associate one stimuli with another stimuli. In operant conditioning the animal is more active. The animal engages in a type of behaviour and this behaviour have certain consequences. A form of behaviour which becomes more frequent as a result of a certain class of response is said to be positively reinforced.

Jablonka noted that despite the distinction between classical and operant conditioning seeming to be very clear; it is a hard distinction to parse from an experimental perspective. Pavlov’s experiments did stop the dog from exploring their environment and so to a certain degree did manage to focus on the dog’s perceptual associations instead of consequences of the dogs’ exploratory actions in the world. Jablonka argues that despite some limited success (Colomb and Brembs 2010), in disassociating the two different forms of conditioning; in reality they form a continuum. Operant conditioning is a type of conditioning involved in self-learning; which involves assigning value to a particular action or movement, and classical conditioning is a form of  world learning which involves assigning value to sensory stimuli (ibid p. 298).

Jablonka defines LAL as follows:

“We define LAL as conditioning that includes both self and world learning and involves the formation of predictive relations between non compound stimuli, actions, and reinforcers” ( ibid p. 321)

To explain LAL Jablonka leans on the phenomena of blocking which she argues demonstrates an organism inhibiting the effects of learning irrelevant stimuli. The psychologist Leon Kamir first studied blocking, where the presentation of a new CS along with an already perfectly predicted CS fails to support new learning (ibid p. 322). Jablonka describes this in terms of an organism predicting reinforcement. She situates this in the prediction error paradigm. What an animal already knows (certain smells lead to food), doesn’t need learning, but if an animal learns that (a bell ringing) also lead to food this will be a ‘surprise’ and will require the animal to update its model of the world. Jablonka parses this as an animal constantly generating predictions about the value of the stimuli it encounters. With a novel, surprisingly reinforced input the most efficient strategy is to adjust the predictions to minimize future surprise (ibid p. 322).

Adopting this approach to LAL can help us explain the nature of blocking:

“A model of blocking posits that the effect of the new concurrent stimulus Y is inhibited because there is no difference between the reinforcing effect of X and that of XY. This makes evolutionary sense: mobile animals with LAL encounter many incidental that co -occur with and already reinforced stimulus but do not contribute to reinforcement, and learning about these stimuli would be a waste of time and energy.” (ibid p. 323).

                          Unlimited Associative Learning and Minimal Sentience

 

Jablonka argues that UAL has four key features:

(1) Hierarchical processing, which enables compound perception and compound action.

(2) Integration between perception and action models.

(3) Memory for compound percepts.

(4) A flexible global reinforcement system. (ibid p. 360)

In essence UAL involves a creature being able to string together non-reflex eliciting input such as a specific conjunction of several features (green, stick shaped, large), or the stringing together of a non-reflex series of actions. For Jablonka with the arrival of UAL we get creatures with the capacity for minimal consciousness. But a problem that she associates with this arrival of consciousness is that unlike with LAL, UAL doesn’t have a built-in capacity to stop overlearning. Hence, she argues these creatures were not only capable of minimal sentience these creatures were capable of severe anxiety.

A Few Brief Criticisms

A key problem with the story that Jablonka tells is that while her behavioural capacity story is well justified her projection of consciousness goes beyond the evidence. Detailed studies over the last fifty years give us strong evidence that intuition aside complex behaviour is not a reliable indication of consciousness. Le Doux recounted some of these reasons in his recent book ‘The Deep History of Ourselves’: (1) Split Brain Patients: when the corpus collosum is cut in human subjects stopping the left hemisphere from communicating with the right hemisphere. Subjects respond to commands that are flashed to the left hemisphere (the non-verbal part of the brain). If ‘Stand Up’ is flashed to the subject then they will stand up. When asked why they will give a confabulated reason. One interpretation of this is that the behaviour of ‘standing up’ is an unconsciously controlled behaviour. (2) Blindsight: After a stroke patients are blind to things on the left side of their visual field. Although the patients claim they cannot see on their left hand side of their visual field they can accurately grasp for objects on this side and perform better than chance on experiments indicating that they were perceptually registering objects on this side even though they had no phenomenal consciousness. Again, this indicates that some complex behaviours don’t need consciousness to perform them. So why assume that creatures in the Cambrian Explosion were conscious? (3) Patients who had their hippocampus removed causing global amnesia. Such patients when giving verbal reports indicating they were not updating their memories. Nonetheless these patients retained learn complex motor tasks. So despite their conscious memory being destroyed they could still learn procedural tasks. Indicating that their complex motor behaviours need not be conscious (Le Doux ‘The Brief History of Ourselves pp 266-268). Overall what these studies indicate is that complex motor behaviours do not require consciousness. So Jablonka’s assumption that creatures in the Cambrian who had UAL also had minimal consciousness is somewhat of a stretch. Jablonka hasn’t done enough to distinguish unconscious motor behaviour from consciousness driven behaviour.

At this stage the empirical doesn’t conclusively support or refute Jablonka’s claims. To use a tired cliché; more research is needed. A possible way out of this impasse is in Le Doux’s claim that a central weakness with neuro-pharmacology is that it is based on animal models that track fear behaviour instead of the feeling of fear. In his book Anxious Le Doux suggested a different way of understanding Anxiety. If future neuro-pharmacological studies based on Le Doux’s recommendations are more pragmatically successful than current techniques, then this would be evidence that his theory of consciousness is superior to Jablonka’s theory.

Once this data is in we will have more evidence to help us decide between the competing pictures of the Cambrian Explosion. We will have data that will help us decide whether the creatures of the Cambrian Explosion were perpetually horrified creatures like characters from a David Lynch Film or whether they were merely beautifully designed unconscious robots competing with each other.

[1] Jablonka and Ginsberg are co-authors of ‘The Evolution of the Sensitive Soul’ throughout this blog-post for ease of reading I will refer to Jablonka as short hand for Jablonka and Ginsberg. I use Jablonka’s name as opposed to Ginsberg because I am more familiar with her work. But the post is about the book they co-authored.

[2] Obviously experiments still go on today on Chimps, Dogs etc. and sometimes these experiments are done for commercial profit and not to cure diseases that plague humanity. However, overall scientists need to justify their experimental practices on animals now to a greater degree than a hundred years ago.

[3] Henceforth Limited Associative Learning will be referred to as LAL.