The “Solitary Forager” Hypothesis of Autism: www.solitaryforager.com

I created a new web page recently to post my “theory of autism.” The theory attempts to explain why autism exists by elucidating its evolutionary history. Consistent with Simon Baron-Cohen’s systemizing theory of autism and with Temple Grandin’s positions, I see most autistic individuals as intelligent and autism as having compensatory advantages. Clearly, sometimes autism is accompanied by disease states, but the psychological "symptoms" of autism are seen here as attributes that would have benefitted a solitary forager (see the table at the bottom).


"To the extent that neurotypical individuals can be thought of as social foragers, autistic individuals can be thought of as solitary foragers."


There has been a lot of recent speculation and controversy over autism and what its existence "means.” A number of theoretical articles have been written on the subject such as the “Neanderthal theory of autism,” the “neoteny theory of autism,” the “extreme male brain theory,” the “imprinted brain theory” and the argument that autism is the “next stage in human evolution.” These are all interesting interpretations some of which may have some explanatory utility. I think that the “solitary forager hypothesis,” however; explains autism from the perspective of natural history.


Please take a look at:  www.epjournal.net/filestore/EP09207238.pdf


You can also find an early and unabbreviated version here: http://www.solitaryforager.com/
Abstract:This article reviews etiological and comparative evidence supporting the hypothesis that some heritable genes associated with the autism spectrum were naturally selected and represent the adaptive benefits of being cognitively suited for solitary foraging. The systemizing theory of autism is extended here and people on the autism spectrum are conceptualized as ecologically competent individuals that could have been adept at learning and implementing hunting and gathering skills in the ancestral environment. Upon independence from their mothers, young autistic individuals may have been psychologically predisposed toward a different life-history strategy, common among mammals and even some primates, to hunt and gather primarily on their own. Many of the behavioral and cognitive tendencies that autistic individuals exhibit are viewed here as adaptations that would have complemented a solitary lifestyle. For example, the obsessive, repetitive and systemizing tendencies in autism, which can be mistakenly applied toward activities such as block stacking today, may have been focused by hunger and thirst toward successful food procurement in the ancestral past. 


Individuals on the autism spectrum share a variety of behavioral traits with solitary species. Both solitary mammals and autistic individuals are low on measures of gregariousness, socialization, direct gazing, eye contact, facial expression, emotional engagement, affiliative need and other social behaviors. The evolution of the neurological tendencies in solitary species that predispose them toward being introverted and reclusive may hold important clues for the evolution of the autism spectrum and the natural selection of autism genes. Solitary animals are thought to eschew social contact as part of a foraging strategy often due to scarcity and wide dispersal of food in their native environments. Similarly, it is known that, due to frequent and prolonged dry spells, the human ancestral environment was often nutritionally scarce as well, and this may have driven human parties to periodically disband. Inconsistencies in group size must have led to inconsistencies in the manner in which natural selection fashioned the social minds of humans, which in turn may well be responsible for the large variation in social abilities seen in human populations. This article emphasizes that individuals on the autism spectrum may have only been partially solitary, that natural selection may have only favored subclinical autistic traits and that the most severe cases of autism may be due to assortative mating. This solitary forager hypothesis of autism is explored in the context of
anthropology, comparative neuroscience, epidemiology, evolutionary biology, neuroethology, and primatology.

 

Table 1: Behavior in autism, then and now

Trait or Symptom	Psychological  Consequences	Implications for Moderns	Implications for Solitary Foragers
High systemizing ability	A tendency to systematically explore the laws governing nonsocial processes	Eccentric or narrow but substantial knowledge and skills	An impetus guiding the acquisition of food procurement techniques
Obsessive, repetitious tendencies	Perseveration in behavior and thought	Repetitious play and need for sameness	Order, structure and autonomous self-regulation
Gaze aversion and absence of shared eye contact	Minimal eye contact and diminished attention to the faces of others	Unfortunate social hurdle	Instinctually prepared not to challenge or provoke conspecifics
Low oxytocin	Reduced social interest, learning and expressiveness	Unfortunately hindered social cognition	Programmed for a socially impoverished environment
Anomalies in anterior cingulate cortex, orbito and medial frontal cortex	Reduced social learning, capacity for empathy and affiliative need	Hindered social integration	Decreased reliance on others
Amygdala hyperactivity	Potentiation of innate and conditioned fears	Excessive anxiety and withdrawal from social world	Healthy caution, and fear of unfamiliar conspecifics
Hippocampal hyperactivity	Hyperaccessibility of contextual and episodic information	Proficiency with spatial tasks and contextual memory	Skill in tests of spatial intelligence

Flashbangs and Flashbulb Memories

M84 Flashbang Grenade

I woke up this morning, at 5:15 a.m. to a loud sound that I was sure was a gun shot. I could feel vibration from the noise in my chest and I could tell that it was happening just outside my window. Without stirring, I waited and listened for something else to happen. I heard violent yelling, then at least three more shots followed, each accompanied by a bright flash of light that filled my room. I heard a person scream and then the words: “break it open, just break it open.” I could tell that the sounds were clearly coming from my next door neighbor’s backyard but then I heard people walking right next to my bedroom window – on my side of the fence. Lying still in bed, I felt like a person with post traumatic stress disorder who brings the battlefield home win their nightmares, except what woke me up was not a dream. Harshly disquieted, I grabbed a bat and went looking for a cordless phone to call 911. After a half-hour of suspecting a violent crime I finally got a hold of the local watch commander who told me that police had served a warrant next door and used flashbangs to gain entry. Flashbangs, also known as stun grenades, are used as incapacitants by law enforcement and the military to subdue and disorient. The grenades detonate with a flash of light that maximally activates all light sensitive cells in the eye, making vision impossible for about five seconds while also producing a blast of sound that disturbs fluid in the inner ear producing mental disorientation.

Once I was apprised of the fact that the noises I heard were law enforcement and not criminal I felt much better. I knew I was no longer in danger. My cat Niko on the other hand, couldn’t understand this and he was engaged in all kinds of nervous behavior that I have never seen from him. I tried my best to calm him but was disappointed that I couldn’t communicate to him that we were safe now. I quickly grabbed my things and left for the bus in an effort to make the 8:00 a.m. statistics discussion section that I teach. On the way out, I saw a swat truck and about 15 camouflaged, masked, heavily-armed men. These images were poignant but I tried to move on mentally with my day. I also tried to become aware of my memories of the event and aware of my responses to it.

Memories of surprising or traumatic events are thought to be much more accessible and are called flashbulb memories. Flashbulb memories are exceptionally vivid “snapshots” of a surprising or consequential event. Highly resistant to forgetting, these autobiographical memories are distinctive, contextually inflexible and thought to represent an adaptive, biological response aimed at preserving information about injurious or otherwise noteworthy circumstances. Studies have shown that, unlike most contextual memories that necessitate the involvement of higher-order association areas (such as the PFC and mediotemporal lobe), flashbulb memories can be brought quickly to consciousness without sustained thought. Thus it seems that our brains are equipped to rapidly reconstitute imagery about fearful or emotionally arousing situations. Normally, when higher-order areas are involved, we need a large number of coactivated representations to drive specific memorial imagery. Flashbulb memories on the other hand, can be brought back in full force with the coactivation of just a few relevant representations.

When I got back from school, stimuli at home were evoking flashbulb memories. I looked at my bedroom window and clearly heard the words, “break it open.” I didn’t summon these words, I didn’t want to hear them. My amygdala and other subcortical brain areas activated the circuits responsible for the words after being triggered by the environment. Clearly, intrusive imagery like this is more frequent and more vivid in schizophrenia or in drug-induced episodes of psychosis. Normally, the areas that cue up this invasive imagery serve as protective devices that are innately sensitive to loud noises, fast movement and threats of danger. Here this form of memory is working against me but in the hunter-gatherer past they would have been forced me to take precautions necessary to ensure my survival.

My conscious self knew better, knew that there was no real danger. But, like my cat, other unconscious brain areas and neural circuits - that don’t speak English - didn’t know this. These unconscious brain modules, like small, scared animals, continued to be emotional simply because they do not have access to the explicit, declarative knowledge that there was no real threat.

Poster Presentation on the Mechanics of Thought

Click on the picture below to see the poster that I created for a recent neuroscience symposium at USC. To find out more about these concepts visit my new website at: http://www.cognitivemechanics.net/.

Abstract
The present analogy for the neurophysiology of thought involves a many-armed octopus grabbing and releasing footholds as it pulls itself from place to place. This is meant to illustrate that the thought process involves a cyclical pattern of cortical activation, coactivation and deactivation. Coactivations (footholds held simultaneously by the octopus) fluctuate as cortical areas that continue to receive sufficient activation energy are maintained, areas that receive reduced energy are released from activation and new areas that are tuned so as to receive sufficient energy from the current constellation of coactivates are converged upon, recruited and incorporated into the remaining amalgam of active areas from the previous cycle. Newly recruited areas contribute their inputs to those of the remaining previous inputs altering the mental representations that are produced. Such a newly activated area, or primed node, corresponds to a cortical module (composed itself of neural assemblies) that, when coactivated with other such modules, unites discrete features of long-term memory into composite, global mental imagery. This model defines an individual thought as the imagery produced in primary and secondary sensory areas in response to a particular set of coactivates in association areas. The thought changes once association areas respond to this imagery with newly activated modules and send their new sum of inputs back to the sensory areas for the creation of modified imagery (reperception). The process whereby these modules fluctuate spatio-temporally is taken to be analogous to the nonlinear stride of an octopus that plants the majority of its arms temporarily while actively repositioning arms that have lost their footholds. The fact that some modules ,within association areas, are conserved (the arms remain planted), during these reciprocal oscillations between top-down association areas and bottom-up sensory areas, is taken to account for the continuity found between successive thoughts. The result is a stream of consciousness where each thought is slightly different than the ones preceding them as newly relevant modules are added and the least relevant ones are taken away.

Introduction

1) How can the thought process, the experience of consciousness and the functionality of working memory be described in terms of brain events? 2) How do features from long-term memory combine together to create original thoughts? 3) What brain events take place when we move from thought to thought?

- Models such as Baar’s global workspace theory, Baddeley’s theory of working memory, Damasio’s convergence-divergence paradigm and Edelman’s theories of reentrance and neural Darwinism have done much to lend perspective and insight into the mechanics of thought progression.

- This model uses an analogy, explained in the abstract above, to describe the process of the progression of thought. Please visit http://www.cognitivemechanics.net/ for a full treatment.

The Octopus’ Arms Represent Cortical Modules

- Unlike subcortical areas, strictly one-to-one, linear activation is probably rare in the cortex. Rather, cortical modules coactivate together to spread the activation energy necessary to recruit the next set of modules that will be coactivated with the remaining modules from the previous cycle. This is highly analogous to the “seafloor walking” behavior seen in the octopus because these animals plant the majority of their arms on the ocean floor while repositioning arms in the back towards the front.

- The longer modules in association areas can be continuously activated, over a series of thoughts, the longer they can influence sequences of bottom-up imagery in a sustained and consistent way allowing modeling, planning and working memory in general.

- It may be correct to say that someone with a working memory deficit has fewer modules to select from, fewer modules bound during coactivation and modules that cannot maintain their activation for as long as they do in other people. Because modules work cooperatively, having fewer modules of less duration will reduce network searching power and specificity.

- Fluid intelligence derives from the number and duration of modules whereas crystallized intelligence derives from the connections between modules and their tuning properties.

- Some modules are retained as coactivates even after a number of thought cycles. This happens when one’s thoughts transition and change but hold a common element constant and is often due to potentiation by the PFC.

- Sometimes modules are not conserved from thought to thought and the “octopus” drops most of them all at once. This happens when one abandons a train of thought and quickly reorients to a new, salient, perhaps emotionally laden stimulus.

- Another component of this analogy is the idea that the octopus will fall if it loses its grip on a sufficient number of branches. Since the body of the octopus is analogous to consciousness this is appropriate because brains become unconscious once coactivation and the accompanying binding (especially in the frontal and parietal fields) is sufficiently diminished.

- The number of octopus arms is set and this represents our fixed, innate capacity for working memory. Even though the number of chunks that can be held in working memory, 7 plus or minus 2, coincidentally coincides with the number of arms an octopus has (8), this is not a reliable indication of the number of modules that can be coactivated in the cortex. It is not clear: 1) how many modules are normally coactivated at once, 2) what organization of neurons or their assemblies constitutes a module or 3) exactly how rhythmic binding plays a role in module coactivation.

- The hippocampus has an ability to detect a set of cortical coactivations and reactivate the rest of the assemblies that were coincident with these in the past in a process called pattern completion. The hippocampus then, has the ability to guide the legs of the octopus toward historically coactivated patterns.

- The PFC helps the octopus control the spatio-temporal layout of coactivations by prolonging activation in modules that correspond to salient concerns in the environment in order to allow the uninterrupted persistence of such features in the imagery, enabling forethought, planning and modeling.

Interactions Between Association Modules and Sensory Imagery

- The process of thinking involves cycles between internally generated imagery and one’s higher-order perception of it- reciprocal priming between bottom-up sensory and top-down association areas. This process is similar to what it would be like to watch a television program that one could control with their ideas, conceptions and conceptualizations.

- The modules in association areas cooperatively converge on sensory modules which combine this unique set of higher-order coactivations into a composite, lower-order, feature-based image. The ability to do this is fine-tuned during early development, makes use of the vast architecture of recurrent (back-propagating) pathways and is accomplished rapidly, based on prior probabilities.

- Importantly, things that follow from our conceptualizations, but that we did not expect to see are routinely rendered in imagery. For instance our sensory areas might pull up the imagery specified by association areas, but elaborate on it with closely associated but unforeseeable embellishments. Thus, the cyclical oscillations of information between sensory and association areas allow them to learn from each other and allow them to integrate their knowledge like two people in a conversation.

- This suggests that one can only perceive the relationship between two abstract ideas if one already has implicit information in the sensory cortex about how to co-represent them in an image.

- As an association node is converged on from nodes upstream, it becomes active and in turn divergently activates the downstream sensory nodes that ordinarily converge upon it. The resultant sensory imagery is then either superimposed over objects perceived in the environment or combined with other features in the mind’s eye. Thus contemplative thought takes place on the same Cartesian stage that sensory experience takes place on. Sense, remembered or reactivated is the substrate of thought.

- The octopus arms (modules) in posterior sensory areas move faster, from module to module, but are can hold a larger number of simultaneous representations. This accounts for the transience of sensory memory but also for its greater capacity (echoic and iconic memory decay faster but hold a larger number of chunks).

- A module becomes implicit, and its features become unconscious, when it is no longer needed - during coactivation with its normal coactivates - to recruit another particular module. 

-Some modules within association areas remain activated because they are restimulated by the imagery that they contributed to. Other association modules that are not restimulated by this imagery deactivate as the projection neurons associated with them stop firing as rapidly.

-In other words, we create imagery in our minds, but we don’t pay attention to every aspect of the imagery just like we don’t notice every aspect of the perceptions that we create of our environment. Thus this analogy of the “TV you control with your mind” is closely related to the octopus analogy because the elements of the imagery that are attended to drive the placements of the octopus’ free arms.


Read the full article that I wrote on this topic here:

http://www.sciencedirect.com/science/article/pii/S0031938416308289