rationalskepticism.org

GrahamH wrote:given things got stuck on whether free will means we make our own selves move or not moving on to 'sholder angels' seems hugely ambitious right now

Harvard law of animal behavior
when stimulations are repeatedly applied under precisely controlled conditions the animal reacts as it damn well pleases

Behavioral variability is a well-known phenomenon. It is so pervasive that the semi-serious Harvard Law of Animal Behavior was coined: “Under carefully controlled experimental circumstances, an animal will behave as it damned well pleases.” It is the source of this variability which is under scrutiny here. The current neuroscientific consensus posits that the source of the variability is noise, rendering the variability random or stochastic. We show here that random noise cannot be the sole source of behavioral variability. In addition to the inevitable noise component, we detected a nonlinear signature suggesting deterministic endogenous processes (i.e., an initiator) involved in generating behavioral variability. It is this combination of chance and necessity that renders individual behavior so notoriously unpredictable. The consequences of this result are profound and may seem contradictory at first: despite being largely deterministic, this initiator falsifies the notion of behavioral determinism. By virtue of its sensitivity to initial conditions, the initiator renders genuine spontaneity (“voluntariness” [30]) a biological trait even in flies.

New models of brain function

Because theoretical work suggests a range of competitive advantages for indeterminate behavior in virtually all animals [19], [61]–[65], [71], the structure of the indeterminacy should be incorporated explicitly into models of general brain function and autonomous agents. What would such future models of brain (or agent) function look like? Nonlinear models displaying probabilistic behavior patterns can in principle be fairly simple [55]. The nonlinear mechanisms need still to be influenced by the environment both in a feed-forward form (the sensorimotor link) [7], [13], [14], [72] and by reafferent feedback control (Fig. 7) [73], [74]. Our data raise the suspicion that future models of the brain may have to implement this or a related component for spontaneous behavior initiation, if they strive to be biologically realistic, out-competing other models/agents. Recently, a new class of agents was introduced, which incorporated some of these ideas [75].

Brains are simultaneously indeterministic and deterministic for a reason

This insight has implications for our understanding of the general function of brains. The most fundamental brain function is to produce adaptive behavior. Adaptive behavior is the ability to orient toward specific goals in the environment and to control actions flexibly in pursuit of those goals. By and large, the every-day world we live in is Newtonian: predictable and deterministic. If we lose balance, we fall, if we neglect obstacles in our path, we collide with them and if we reach for an object, we can grasp it. Hence, no ambulatory animal could survive without its set of adaptive, hard-wired sensorimotor rules shaped by evolution and tuned by experience. No male house fly would ever catch its mate. At the same time, the world is full of surprises: the unexpected pursuit by a male house fly, the rejection of your manuscript or the next move by your chess opponent (or a predator). In such cases, not even the most complex stimulus-response programs (learned or innate) will help an animal in evading the undesired surprises and obtaining the desired ones. If the evasive actions taken by the female house fly were predictable, males could short cut and catch them with much less effort. It is essential to not leave the generation of behavioral variability to chance (i.e., noise), but to keep it under neural control (i.e., nonlinearity). As such, evolution can fine-tune the balance between sensorimotor mapping and superimposed indeterminacy, defining the required compromise between spontaneous and reactive behavior. The variability of systems under tight constraints will be explained mostly by noise (because the variability under neural control is minimized, such as escape and pursuit responses in flies) [76], whereas noise may play a very small role in generating variability of less constrained behaviors (such as the ones observed here or the evasive actions taken by female house flies) [19], [20], [77]. This notion of brains operating on the critical edge between determinism and chaos has also been used to describe human magnetoencephalographic recordings [78]. Analogous to Heisenberg's uncertainty principle [79], [80], much behavioral variability arises not out of practical constraints, but out of the principles of evolved brain function. In “What is Life?” Erwin Schrödinger claimed that fundamental indeterminism would never arise in the living world [81]. Today however, the picture emerges that as much as simple taxis, mate pursuit or course control require deterministic sensorimotor programs [7], [13], [14], [56], [57], [76], more complex interactions require behavioral indeterminism, as evidenced by recent studies in game theory [61], [63], [65], exploration/foraging behavior [71], feeding [82] and pursuit-evasion contests (“Protean Strategy”) [19], [23], [77], [83]. Clearly, deterministic behavior will be exploited [23], [84] and leaves us helpless in unpredictable situations [30], [85]. Brains indeed do throw the dice–but by refuting the notion of stochasticity our results imply that they have exquisite control over when, where and how the dice are thrown [86].

Spontaneity is the basis for operant behavior

If unpredictability is so important, why is the ‘random number generator’ in the fly brain not perfect? For one, perfect unpredictability might not be required for survival. In addition, variable behavior might serve a second function. Variable, spontaneous behavior is the only way to find out which portions of the incoming sensory stream are under operant control by the animal's behavior. If much of the variation in this stream is due to random noise (i.e., Gaussian), behaving in a non-Gaussian way may aid in the detection of those variations which can be brought under behavioral control. Given these considerations and that our data imply a memory for past events influencing behavior initiation, it is tempting to perceive such mechanisms of spontaneous behavior initiation as the basis for operant behavior, operant conditioning and habit formation [74]. Following this notion, the ecologically so advantageous heavy-tailed searching strategy may be brought about by constantly engaging motor outputs and monitoring their effects in a decision-based queuing process. Such a process prioritizes certain items in a list over others (for instance yaw turns over thrust control, roll or proboscis extension) and has been shown to lead to heavy-tailed behavior patterns [33], [67]. These considerations lend credence to an early, rarely cited cognitive hypothesis on the significance of behavioral variability in vertebrates [28] and suggest that it is actually much more profoundly valid throughout the taxa, with the prospect of studying its biological basis in a genetically tractable model system. Identifying the neural circuitry housing the initiator will be the logical next step in this research.