This is part of a series on Simona Ginsburg and Eva Jablonka’s book: The Evolution of the Sensitive Soul, a book focused on the evolution of minimal consciousness. This particular post is on the capabilities Ginsburg and Jablonka (G&J) see as necessary to attribute consciousness to a particular species. The capability they focus on is learning, but not just any kind of learning, a type of sophisticated learning they call unlimited associative learning.
There are many different types of learning, but they can be grouped into two broad categories: non-associative learning and associative learning, with associative being the more sophisticated.
Non-associative learning includes habituation and sensitization. Habituation is when a sensory receptor responds less frequently to a constant or repetitive stimulus. It’s why you don’t feel your clothes against your skin (until I called your attention to it) or the pressure of the piece of furniture you’re sitting in against your body.
Sensitization is the opposite. If there is no stimulus for a long time, the sensory neuron is more likely to respond when one suddenly arrives. Or if it arrives in an unexpected pattern (such as the feeling of something crawling on your leg). Or if the previous stimulus was painful, then a relatively mild stimulus may still lead to an intense reaction.
Non-associative learning takes place in all kinds of living systems, including unicellular organisms. In animals, in the cases I described above, it actually takes place in the peripheral nervous system. Although it also happens in the central nervous system. More sophisticated learning is built on top of it.
Historically, associative learning has been categorized into two categories: classical or Pavlovian conditioning, and operant or instrumental conditioning.
Classical conditioning is best exemplified by the case of Ivan Pavlov’s dogs. Initially, in an experiment, the dogs would salivate when food was presented to them. But if each time the food was presented, a bell was also rung, the dogs would start to salivate on the bell ring. Eventually they would salivate on the ring so even if no food was presented. Classical conditioning is association of two sensory stimuli, the conditioned stimulus (the bell) with the unconditioned stimulus (the food).
Operant conditioning involves association between an action and a reinforcement stimulus. For example, if a rat in a cage, through random action and exploration, accidentally jumps on a lever, and a food pellet is released, the action (pressing the lever) becomes associated with a reinforcement stimulus (the food). For it to be a reinforcement, the stimulus must involve some existing value for the organism, either attractive (like food) or aversive (like electrical shock).
G&J, somewhat pushing back against the traditional nomenclature, labeling classical conditioning as “world learning”, because it involves association between external stimuli. They label operant conditioning as “self learning” because it involves associating an action by the self with reinforcement, a sensory stimulus.
- Non-associative learning
- Associative learning
- Classical conditioning / World learning
- Operant conditioning / Self learning
G&J state that associative learning requires a brain. So although we might see non-associative learning in creatures like ctenophores (comb jellies), we only see associative learning in creatures with some sort of central coordinating system. That said, the definition of “brain” here is fairly liberal. So many worm like creatures with slightly larger ganglion toward the front of their body seem to meet the standard.
(I found this brain requirement surprising, since classical conditioning is often said to be widespread. But after reading G&J’s assertion, I tried to track down cases of classical conditioning in primitive organisms. The main example was a starfish; G&J mention the one study showing it but dismiss it for methodological reasons. They also briefly allude to studies finding it in unicellular organisms, but don’t seem to find those studies convincing.)
Primitive creatures generally only have what G&J call limited associative learning (LAL). With LAL, the associations that form are relatively simple. Although “relative” is a key word here, because even with LAL, things can get complex pretty fast.
But this isn’t the type of learning that signals minimal consciousness. For that, we need a type of learning that allows associations between compound stimuli integrated across multiple modalities (hearing, sight, smell, etc) and complex combinations of motor actions. When the capabilities for these types of associations start to arise, the possible combinations quickly increase exponentially, becoming virtually unlimited.
It is this type of learning: unlimited associative learning (UAL) that G&J see as a key indicator of minimal consciousness. UAL requires sensory integration through multiple hierarchies, forming an integrated sensorium. It also requires integration across possible motor systems, an integrated motorium. And the sensorium and motorium become integrated with each other, with a concept G&J refer to as association units. (G&J don’t use the words “sensorium” or “motorium”, but I find them helpful here to summarize a lot of detail.)
Each layer in the sensory hierarchies make predictions based on the signals from lower layers. The lower layers respond with prediction error signaling, making the communication between each layer both feed forward and feed back in a recurrent fashion. It’s with this sustained recurrent signalling that temporal thickness and synaptic plasticity is achieved, leading to memory and learning. And when it spreads to motor systems, we get the global workspace effect.
It’s important to note that G&J do not claim that UAL is minimal consciousness, only that it is a key indicator of it. In order to be capable of UAL, a species must have the underlying architecture, including the attributes listed in the last post.
However, UAL represents crucial capabilities that likely make minimal consciousness adaptive. While it’s possible to see animals that are minimally conscious who, due to injury, pathology, or immaturity, show signs of minimal consciousness but aren’t capable of UAL, the healthy mature members of the species should be capable of it. In this view, UAL is a key driver of the evolution of minimal consciousness.
In many ways, UAL resembles one of the criteria that Todd Feinberg and Jon Mallatt used for affective consciousness in their book, The Ancient Origins of Consciousness. Feinberg and Mallatt called this criteria “global non-reflexive operant learning”. (Although they didn’t elaborate on this, and I didn’t find them to necessarily be consistent with the “global” or “non-reflexive” part in the studies they cited.)
As many others do, G&J take issue with Feinberg and Mallatt dividing primary consciousness up into three separate divisions: exteroceptive, interoceptive, and affective consciousness. For G&J, there is only one consciousness, which at any time might be focused on exteroceptive, interoceptive, or affective content.
That being said, G&J reach conclusions very similar to Feinberg and Mallatt’s on which species have minimal consciousness: all vertebrates, including fish, amphibians, reptiles, mammals, and birds, as well as many arthropods such as ants and bees, and cephalopods such as octopusses.
In the last post for this series, we’ll discuss some additional areas that G&J explore, and I’ll provide my thoughts on their overall approach.
What do you think of UAL (unlimited associative learning)? Do you think it’s a valid mark of minimal consciousness?