Each stage is modulated by several interacting systems including a cognitive system that selectively controls and regulates survival strategies along an abstract to concrete threat continuum. Internal probabilistic models subconsciously learn about, and facilitate responses to, threat. As one moves from predictive to defensive systems, innate and fixed systems are increasingly engaged.
No human behavioral model based on threat context, such as those laid out by Fanselow and Lester and Lima and Dill has been put forward. We further link these ecological models to the neuroanatomical circuits that underlie survival. We also incorporate recent advances in cognitive neuroscience including recent work on cognitive reappraisal and cognitive control and how these can tune both learning and survival strategies.
The SOS incorporates recent advances in learning theory e. The conscious prediction and simulation of future threat occurs during preferred safety context and pre-encounter threat and allows animals to prepare for, and flexibly attend to, potential danger. In humans, the highly developed ability to envisage, simulate and predict future scenarios allows us to modify our current behavior to prepare, escape, or even avoid possible future dangers Suddendorf and Corballis, The prediction of threat results in precautionary behaviors, such as increasing alertness, environmental surveillance and what we call pre-encounter avoidance i.
Furthermore, the prediction system results in prevention strategies, such as niche construction Odling-Smee, , risk dilution through living in the safety of groups, building safe havens e. While basic predictions occur through simple Pavlovian stimulus-response learned associations and instrumental actions, complex predictions involving imagination, simulation, and analogical reasoning, may, in terms of extent, be most enhanced in humans.
Prediction formulations allow humans to use memories of past events to simulate or imagine the future and to consider what steps one might take in order to optimize escape from a threat Hassabis et al. Imagination potentially allows one to remotely simulate unpredictable predatory behavior while minimizing predatory contact and energy exertion, thereby increasing the likelihood of escape. Simulation and imagination. Although rodents seem to show rudimentary forms of simulation e. One benefit of prospective systems is the ability to anticipate threat as well as highlighting escape strategies without experiencing actual danger.
Simulation allows us to foresee and pre-live danger that is presently absent Suddendorf and Corballis, Episodic memory stores personal memories about everyday experiences and therefore is critical to simulation and higher forms of prediction Hassabis and Maguire, Episodic memory is not only crucial for remembering past events, but also supports so-called mental time travel, whereby humans both counterfactually remodel the past, and foresee, plan and change the future Suddendorf and Corballis, While not a universal ability, mental time travel has been demonstrated in Great Apes Mulcahy and Call, and Corvids Dally et al.
Recent studies have shown that thinking about future consequences of one's decisions can influence current decision-making Peters and Buchel, and it is possible that future-oriented survival encoding produces superior memory retrieval for survival-relevant information Nairne et al. Predictive coding. Predictive coding is the theoretical proposal that the brain actively infers sensory input.
Consequently, humans can efficiently disambiguate present from future information, thus allowing faster and optimal responses to threat.
Summerfield et al. These findings were interpreted as evidence that the medial PFC resolves perceptual ambiguity by matching what is expected or predicted to what is observed. Later research replicated these findings, further demonstrating that predictive coding is associated with activity within the medial PFC Summerfield and Koechlin, These findings suggest that the brain makes active inferences about the sensory experiences we are likely to encounter.
The formulation of predictions by the brain may serve to make quicker and more accurate decisions about potential danger in the environment. During the preferred safety state and pre-encounter threat, the ability of an organism to make accurate predictions concerning potential threat is highly adaptive and enables it to flexibly change behaviors to protect itself from future predation. We propose that prevention takes two forms:. Niche construction.
Humans, and many other animals, deploy various prevention strategies to reduce threats, including alteration of the environment. Put simply, if it is possible to predict a predatory attack, it is often possible to prepare for it in advance.
This process, referred to as positive niche construction, Odling-Smee, involves active alteration of the environment to increase the likelihood of survival. Animals will alter their environment by building nests, burrows or tree holes to protect themselves and their offspring. Rodents also show an increased fear of open areas e. Humans utilize advanced technology and cooperation to optimize prevention strategies both in terms of scale and effectiveness by building large walls and fortresses, living inside safe homes and constructing prisons to contain the threat from dangerous criminals.
Humans are more flexible and ingenious in the implementation of prevention strategies and may do so without any reason or in response to threats that may be encountered in the future. The knowledge that one is safe reduces the stress of predation, allows for delayed dispersion of the offspring and allows for activities that might otherwise be risky to survival. Group living. Evolutionary theorists have proposed that one key reason why animals live in groups is to protect themselves from predation. For example, Hamilton's Selfish-Herd hypothesis predicts that aggregations emerge from the organism's attempt to avoid predators resulting in a type of social gravity whereby individuals move toward other members Hamilton, This theoretical stance has been supported by studies showing risk dilution i.
Therefore, group living is a key prevention strategy resulting in increased protection from threat. Detection of a potential threat initiates the post-encounter phase, which in turn instigates a set of predictable behavioral strategies.
These strategies involve biological systems that have evolved to orient toward salient events Ohman et al. Mogg and Bradley propose that the goal of attention is to facilitate the detection of danger, and these threat biased attentions may take several forms. Todd et al. These authors further propose that this may be a form of emotion regulation.
Affective-biased attention is driven by bottom-up systems, prone to learning and acts as a filtering process tuned and retuned over development Todd et al.
Attention therefore, may, be driven both by a fast, hard-wired system as well as by a sophisticated top-down filtering mechanism supported by predictions. Threatening stimuli cause on-going behaviors to cease, and lead to freezing and the orientation of attention toward the threat Blanchard et al. Heightened vigilance is costly in terms of energy, loss of foraging opportunities, and disruption to ongoing goal-directed behavior Eysenck, Vigilance is therefore fleeting and restricted to times when high-risk situations are predicted Lima and Bednekoff, An advantage of the prediction system is that it allows the animal to efficiently direct the vigilance system to detect danger early, disambiguate stimuli, and ignore less salient information.
Heightened vigilance is accompanied by tonic catecholaminergic action that increases environmental scanning and sensory signal processing at the expense of selective filtering Sara and Bouret, While the signals processed contain more noise, broader sampling likely increases the probability of detecting potentially relevant stimuli outside of the current task set and represents a conservative strategy to detect threat.
The prediction system may act as a balancing mechanism to optimize behavioral selection and reduce the disadvantage of noisy signals. Early detection via increased vigilance provides for additional time allowing consideration of different strategies to escape threat. Moreover, different pathways within the visual system may be engaged by different types of threat, with magnocellular pathways suggested to process low spatial frequency visual information and parvocellular pathways suggested to process high spatial frequency visual information.
Brain imaging studies of attention to threat have been employed to examine the neural substrates of emotion processing in humans, and typically implicate the amygdala. Pictures of angry faces evoke increased activity in the amygdala and parietal cortex which suggests their involvement in attention to danger signals Mohanty et al. Ventrolateral PFC and the temporo-parietal junction TPJ , on the other hand, are proposed to be involved in directing attention toward novel or new stimuli Sylvester et al.
High levels of anxiety in humans may predispose one to possess a greater attentional bias to threatening or potentially threatening stimuli. In support of the role of the amygdala as an emotional saliency detector, damage to the amygdala has been shown to attenuate the processing of rapidly presented aversive words shown in quick succession, known as the attentional blink. Measures of state anxiety have been shown to positively correlate with frontal and amygdala activity during the presentation of threatening faces Bishop et al.
Increased amygdala activation to fearful faces has also been observed in individuals scoring high on measures of trait anxiety Ewbank et al. Interestingly, highly anxious subjects Bishop et al. In conjunction with the prefrontal cortex, the amygdala may work to cue an individual to environmental signals of interest Schafer and Moore, In the case of unpredicted danger, a prediction error occurs, triggering the engagement of the attention system and providing the animal with rudimentary information about the threat.
The individual is given little if any time to prepare the most optimal course of action. Cortical regions such as the inferior parietal cortex are known to be involved in attentional processing directed toward salient and novel environmental stimuli Gottlieb and Balan, The directed attention system is also influenced by midbrain regions, including the superior colliculus Knudsen, , parietal cortex, pulvinar and motor responding areas Aston-Jones and Cohen, The superior colliculus is a crossmodal structure with motor layers that prioritize locations based on stimulus saliency and motor goals Fecteau and Munoz, , and cholinergic and GABAergic circuits involved in spatially selective enhancement of attention Knudsen, The superior colliculus relays information to the forebrain about salient events Knudsen, Midbrain attentional capture systems are therefore mechanisms that help to protect against the predator's stealth and surprise.
Threat orienting is clearly broader than just attention and involves the whole cognitive system including perception, attention, and memory. Individual differences at this level would mirror the processes at the Prediction System level with, for example, anxious people having a higher incidence of false alarms or bias because the system is configured conservatively Mogg and Bradley, During threat assessment one needs to evaluate the context in which the threat is encountered and generate an appraisal of danger Blanchard et al.
Human crisis management theory proposes that responses to extreme threat include assessing a negative event, determining a response option and evaluating the utility of the response option Sweeny, We propose that there are several sub-stages some functioning in parallel involved in assessing and acting upon information during post-encounter threat:. Post-encounter freezing.
When a potential threat is encountered, the first behavioral response of the animal will be to freeze—a form of passive coping, defined as an absence of all behavior except respiration Bolles and Collier, Freezing allows for improved risk assessment by the animal and reduced detection by the predator, which in turn allows more time to make the optimal response. Defensive freezing occurs when a threat is detected and, in instances such as these, the amygdala and extended systems may compile relevant environmental information and signal the degree of threat to the vPAG Fanselow, Indeed, efferents from the medial central nucleus of the amygdala CeA to the vlPAG are not only critical to instigating freezing, but also to suppressing other motivated behaviors such as foraging and mating LeDoux, Threat monitoring.
Threat monitoring is likely to engage yet another set of neural systems that includes, but is not limited to, the PFC and amygdala. One additional proposed region is the bed nucleus of the stria terminalis BNST. The BNST is implicated in threat monitoring and vigilance and strongly interconnected with the CeA and insula and has been suggested to act as a relay center that coordinates motor, autonomic and defensive reactions during sustained threat Davis et al.
Along these lines, the BNST may monitor signals representing threat escalation in the environment Davis and Whalen, ; Walker et al. Together, the amygdala and BNST may keep track of escalating threat levels e. Optogenetic work, however, suggests that the anatomy of the BNST is more complex than previously believed. For example, recent evidence shows that while the oval BNST independently promotes states of anxiety, other anxiolytic roles are found for the anterodorsal BNST Kim et al. Safety seeking.
With the added benefit of increasing the likelihood of escape from predators, monitoring the location of safety is one strategy by which to decrease fear. Ecological theorists propose that animals maintain a margin of safety from predators, which is the difference in time to reach cover by prey and predator Dill, Elland and Eller have shown that gerbils use the most optimal trajectories to a safe refuge Elland and Eller, Safety searching is also particularly prevalent in a number of affective disorders in humans.
When under threat, the sight of safety signals reduces fear Gray, Indeed, when subjects are placed close to a safety exit, measures of fear decrease Carter et al. Safety cues have also been observed to abolish innate defense mechanisms in rodents, such as threat-related analgesia Wiertelak et al.
One region involved in safety learning may be the vmPFC. Activity in this region is increased in spider phobias after successful reduction of fear via cognitive behavioral therapy Straube et al. Others have shown that a safety stimulus during an aversive experience results in increased activity in the vmPFC Schiller et al. Threat value. How the organism responds to a potentially threatening stimulus is largely dependent on the threat value it ascribes to the stimulus, with the amygdala and vmPFC central to this process.
The amygdalae basolateralis BLA is suggested to be involved in the encoding of emotional events. For example, researchers have shown that activity in distinct neuronal populations in the anterior BLA coincided with emotional state transitions between high and low fear. The CeA, on the other hand, is a major output center, and may be involved in the behavioral expression of fear Balleine and Killcross, The CeA may steer threat responses in the midbrain through its connections to the hypothalamus via neuropeptidergic oxytocin signaling Viviani et al.
More recently, exciting research in rodents using optogenetics and electrophysiology has implicated BLA-CeA microcircuits in the control of anxiety Tye et al. The amygdala may therefore function as a gatekeeper or switch that first determines the threat value of a stimulus and then coordinates the appropriate reactions to that stimulus, both defensively and viscerally Price, While the degree of danger posed by a threat is an important component of models of threat value, another component is implicated in the calculations relating to the likelihood of threat escape by the animal.
Here, the PFC may be particularly important, playing a major role in coordinating and instigating responses to risk assessment. Threat exposure tests in rodents have implicated a coupling between the infralimbic il PFC and the ventromedial orbital PFC. That is, the ilPFC is involved in the careful evaluation of situations involving threat and the ventromedial orbital PFC facilitates ilPFC-mediated adaptive behavioral responses via inhibition of prepotent avoidant responses Wall et al.
As we discuss later, the dorsolateral and ventrolateral zones within the PFC have been associated with the active inhibition of attention toward distractors and emotional reappraisal of prepotent responses to distractors, or cognitive control of emotion Ochsner and Gross, ; Goldin et al. Predicting the actions of the threat. Furthermore, action prediction involves producing multiple simulations in order to predict the actions the threat is likely to take, and the ensuing consequences of each action. Therefore, the prediction system plays a critical role in how we respond to threat, especially when the organism has time to choose between various escape options.
There may be many possible actions but whether the most optimal action is chosen will depend on the quality of information available to the prey. Cortical brain regions, such as the superior temporal sulcus, have been shown to respond to multisensory information such as sound and vision, e. These regions may support the calculations suggested by Bayesian computational approaches to describe behavior, discussed later. Action preparation and directed escape. Directed escape is when the organism avoids the post-encounter threat by actively choosing the most appropriate escape actions.
Volitional action under predation is likely to involve the neural systems that underlie preparatory motor and aversive systems. Self-initiated actions may be enabled via activation of the supplementary motor area SMA. For example, cells in the SMA respond to self-initiated movements Romo and Schultz, , while ablation of the SMA and cingulate motor areas results in disruption to volitional movement Thaler et al. Furthermore, the basal-ganglia acts as an interface between emotion and motor responses, thereby playing a key role in action selection and allowing the animal to transform affective information into a motor response Stocco et al.
Concerning aversive systems, the amygdala is one likely candidate involved in aversive-biased action choice. For example, ablation of the rat CeA suppresses the behavioral responses elicited during exposure to a threatening stimulus, but preserves the ability of the rat to redirect its course of action in order to avoid subsequent exposure to an aversive stimulus.
Conversely, ablation of the BLA renders an aversive stimulus unavoidable by the rat, despite the rat exhibiting normal behavioral responses to the feared stimulus Killcross et al. Recent fMRI evidence in humans has shown that the insula is involved in the bodily urge to initiate motor actions Yu et al. Furthermore, the vlPFC which includes right inferior frontal gyrus [IFG] receives direct input from the striatum Middleton and Strick, and is part of the cortico-striatal-pallidothalamocortical loop. Research in non-human primates also suggests that the lateral PFC is involved in planning future actions Mushiake et al.
Dorsal parts of the ACC dACC are connected to the premotor cortex and amygdala Bates and Goldman-Rakic, and, as such, are thought to modulate both the control and monitoring of action Amodio and Frith, Defensive strategies instantiated in the midbrain and hypothalamus are typically evoked during circa-strike attack. A fast-acting reaction system has obvious evolutionary benefits and perhaps, not surprisingly, this reaction system resides in the oldest regions of the human central nervous system.
Price points out that the first mammals were often preyed on by reptiles and birds and consequently the mammalian brain evolved to enable quick instinctive reactions Price, Immediate threat responses were, and continue to be, hard-wired spinal reflexes that provide rapid reactions to threat Lee et al. The FFF-system also provides fast reflexive responses, but tends to be more sophisticated. For example, when under direct attack i.
Escape in this context is therefore indirect where the organism attempts to terminate exposure to the attacking or perceived attacking threat, yet has limited plan of action Gray, The PAG is a midbrain structure that encircles the cerebral aqueduct Bandler et al.
Human fMRI studies also show a switch from the ventral prefrontal cortex to the midbrain PAG area the closer a threat moves towards its target Mobbs et al. More specifically, the PAG is responsible for at least two evolutionary conserved types of coping behaviors:. Passive coping. Passive coping is typically associated with freezing during threat detection and assessment and is instigated by the vlPAG and its connection with the medial CeA Bandler et al.
A recent optogenetic study showed that inhibitory microcircuits in the lateral subdivision of the CeA gate the medial CeA output, thereby controlling conditioned freezing responses Haubensak et al. Recent models of freezing hold that different subtypes of freezing behavior are evoked by distinct columns within the PAG, and that each freezing subtype serves a different function Brandao et al.
For example, Brandao et al. Furthermore, stimulation of the vPAG results in a form of freezing that is associated with the recovery element of the defense—recuperative process. Freezing induced by either dPAG or vPAG stimulation is hypothesized to occur when threat is highly imminent or when the animal has been attacked. Thus, freezing may take several forms, some enacted by post-encounter threats, others when the threat is high in intensity such as that experienced during circa-strike threat.
Active coping. For example, microinjections of excitatory amino acids placed in caudal portions of the dlPAG result in flight behaviors Keay and Bandler, and chemical stimulation of the dlPAG elicits uncoordinated panic-like behaviors such as vigorous running and jumping Deakin and Graeff, ; Bandler et al.
Moreover, lesions to the dlPAG eradicate such bursts of activity Depaulis et al. In humans, activity in the PAG is observed during highly proximal threat Mobbs et al. In humans, panic symptoms are thought to be mediated by the dPAG and panic disorder patients show abnormal gray matter density in this region Uchida et al. Panic disorder is proposed to be associated with the dorsal raphe nucleus DRN -periventricular pathway which includes projections between the hypothalamus and PAG Deakin and Graeff, Others suggest that the PAG detects respiration and panic results from feelings of suffocation Schimitel et al.
The hypothalamus and PAG are key brain regions involved in the fight responses that occur as a last ditch attempt to deter predators. Lin et al. The dPAG is directly connected to the hypothalamus and is critical for active coping behaviors including fight responses Bandler et al. Stimulation of the PAG has been shown to elicit aggressive behavior Potegal et al. It has been suggested that the PAG, amygdala and hypothalamus together may comprise a rage circuit Panksepp, Indeed, the PAG has been suggested to play a role in evaluating the emotional content of frustrating events, perhaps, through its connections with hypothalamus, medial PFC, and insular cortex Bandler, The presence of an escape route may, in part, determine an animal's decision to either freeze or flee from danger Blanchard and Blanchard, Studies of learned helplessness in rodents demonstrate that, when faced with inescapable electric shocks in one environment, rodents do not attempt to escape electric shocks in a different environment Seligman and Maier, Neurobiological, combined with pharmacological, work has shown that the DRN receives signals about the controllability of the threat from infralimbic and prelimbic sectors of the ventral mPFC in rodents and that Muscimol knockout of this region results in indiscriminate firing by the DRN Amat et al.
Interestingly, in healthy humans, the mPFC, including the rostral ACC, becomes active when subjects are chased by a highly inescapable threat Mobbs et al. The DRN, which contains around 30, neurons in the rodent, is unlikely to modulate complex processes Maier and Watkins, , yet it receives dense connections from regions where complex signals are processed in the forebrain, such as the amygdala and PFC Amat et al. The DRN is a major component of the 5-HT system and, as a site of action for serotonin-specific reuptake inhibitors SSRIs , is thought to be critical in the pathogenesis of anxiety and panic Deakin and Graeff, ; Maier and Watkins, The importance of analgesia is clear—it facilitates escape by reducing pain in the injured animal.
The alternative is that the animal is unable to move due to intense pain or tissue damage, and will most likely die as a consequence. Analgesic systems are likely to be evoked prior to attack, for example, when the animal is pursued by a predator.
The PAG, together with the dorsal horn of the spinal cord and several cortical areas Petrovic et al. Analgesia might require imagined or anticipatory activation of the US representation in order to prepare the organism for a nociceptive outcome Hollis, This process, which accompanies the Post-Encounter stage, is thought to evoke the endogenous opioid system Fanselow and Lester, Stimulation of the rodent lateral or dorsal PAG results in heightened threat and non-opioid-dependent analgesia Comoli et al.
In humans, the PAG is active during both placebo and opioid analgesia Petrovic et al. The degree of affect and the ability to regulate it may determine the amount of cognitive flexibility available being cool under pressure vs. One interesting proposal is that individual differences in these different proclivities will relate to psychopathology. We propose that survival strategies are influenced by two core systems.
Modulatory systems have direct control over the five survival strategies of the SOS. On the other hand, the learning system optimizes survival strategies and modulatory systems by providing probabilistic information and drawing on other information that is relevant to the situation i. Modulatory Systems can override Learning Systems. For example, our own personal encounters can override those learned vicariously. Given the sheer diversity of threat humans encountered on their voyage to conquer the world, it is clear that we needed a flexible system that controls how we appraise e.
An efficient system should flexibly tailor responses to specific circumstances via a set of ecologically-learned actions which would confer the greatest benefit to the survival of species. Two ways of actively controlling a survival behavior are through suppression actively keeping threat or information about threat out of mind and reappraisal—actively changing the way one thinks about a threat or information pertaining to threat.
While most prominent during prediction and threat assessment, these deliberate conscious processes clearly influence all survival strategies of the SOS, albeit with decreasing efficacy as one moves down the defense gradient. Indeed, Ohman and Mineka point out that automatic responses, such as those instantiated in the FFF-system, are likely to be impenetrable to conscious cognitive control. In the face of this decreasing control, there is little doubt that conscious reappraisal would play a major role in both prediction and threat assessment systems when the threat is distal and there is time to think.
Candidate neural regions involved in cognitive appraisal include dorsomedial, ventrolateral vl and dorsolateral dl PFC. The vlPFC has been suggested to be involved in reappraisal of emotion Wager et al. The dlPFC has been implicated in cognitive operations such as behavioral selection, top-down control of memory, attention maintenance and suppression of unwanted memories Anderson and Phelps, ; Baird and Fugelsang, ; Gordon et al.
In relation to the rostro-caudal model of cognitive control, the dlPFC has been implicated in sensory and contextual levels of control Badre and D'Esposito, Given these roles, the dlPFC is an important part of the behavioral inhibition circuit that controls prepotent emotional responses, otherwise known as a cortico-striatal-thalamocortical loop Masterman and Cummings, ; Owen et al. Systems that detect and resolve conflict represent an important extension of top-down control processes by PFC Cavanagh et al.
Again, these processes would presumably be highly beneficial during threat assessment. Closely allied with the active processes of reappraisal and suppression is the ability to passively regulate the survival circuit. A candidate region for this operation is the subgenual ACC sgACC —a region known to play a role in mood regulation, extinction, stress responses and learned fear Phelps et al.
Interestingly, the sgACC is connected to the amygdala and other parts of the threat circuitry i. Mayberg et al. Following stimulation of the sgACC, remission of depression was observed in the majority of patients Mayberg et al. More recently, we have shown that when subjects are trained using an emotional working memory task, they become better at reappraisal when viewing negative stimuli. This increased ability is predicted by increased activity in the fronto-parietal network and the sgACC Schweizer et al.
Although more research is needed, this suggests that the sgACC interacts with cognitive networks involved in affective regulation and suppression. Signals from physiological and hormonal systems serve as critical contexts Maren et al.
For example, Schachter and Singer demonstrated that when people are given a sham vitamin injection which in reality was a norepinephrine agonist that increases autonomic arousal , the cognitive labeling of their emotion experience was altered. As Schachter and Singer explained, subjects search the context for an explanation of their physiological experiences, irrespective of whether the context was responsible for generating those experiences Schachter and Singer, The dACC activates during sympathetic-excitation including heart rate, blood pressure and pupil dilation Critchley et al.
Research has shown individual differences in the ability to detect one's internal bodily state.
When Critchley et al. The authors suggest that the anterior insula is involved in the subjective awareness of visceral feelings Critchley et al. The importance of interoception on decision-making has been exemplified by Dunn et al. Critical to the SOS is the idea that animals have to weigh the risk of predation with a need to satisfy their metabolic needs Sapolsky, ; Barrett, These two pressures are in direct competition with each other. Closely related to this phenomenon is Lima et al. Their model was based on the observation that ground squirrels sometimes eat food immediately when the threat of predation is high, but other times take food to the safety of their tree.
The latter strategy is inefficient in the sense that more energy is consumed when carrying food back to safety—energy that could be used to escape predators. While the authors supported this trade-off, they also found that when the food was close to the tree, the squirrels would carry the food back to the tree, suggesting that when energy consumption was relatively low, the optimal behavior was to prioritize safety. However, studies show that hunger changes the dynamics of the energy-predation risk trade-off Sih et al. Milinski and Heller showed that hungry Sticklebacks will change feeding behavior in an effort to maintain predator vigilance.
This cost-benefit behavior extends to arthropods. For example, hungry spiders Pardosa Milvina show a pattern of consuming the same amount of food when under predation, compared to non-predation. However, when sated, they consumed significantly fewer prey when under predation risk Persons et al.
Although little work has been carried out in humans, Symmonds et al. Furthermore, people make poorer health judgments when hungry Tal and Wansink, Together, it seems that when metabolic needs are high and when starvation is imminent, the SOS would be reconfigured to aid the immediate optimal survival response e.
While innate neural mechanisms prepare us to react to ecological dangers, our experiences are responsible for shaping how we navigate the world. A critical component of the SOS is the ability to continually update and modify responses through learning e. Flexible learning systems modulate both soft-wired higher order systems such as prediction, and basic associative systems i. While associative learning is a component at all levels of the SOS, more complex predictions and simulations involve probabilistic models that increase the effectiveness of behavioral responses. Probabilistic models can be learned and refined via direct experience with threats or by observing others under attack.
Threat encounters that do not result in death provide valuable information that results in an increased ability to avoid future threats with specific predators. Associative learning is conserved across most species, providing quick and decisive actions based upon experience. Given its importance and effectiveness across evolutionary history, this type of learning plays a role in all levels of the SOS model, influencing and guiding many behavioral actions.
For instance, animals will associate a particular context, event or particular actions with threat. These features become bound together such that future encounters with a similar context, event, or particular actions evoke representations of their consequences, resulting in physiological changes and prompting the organism to action. This type of learning is highly adaptive, quickly generating a more accurate representation of the world and its potential threats in order to optimize survival behaviors.
Simple computational models proposed by associative learning theories are effective in describing how organisms learn about threats. Pavlovian conditioning involves the strengthening of a stimulus-outcome association, while instrumental conditioning involves the strengthening or weakening of a behavioral action based on its consequences.
These simple types of learning can be further enriched, For example, in Pavlovian-Instrumental Transfer PIT an instrumental behavior is influenced by a Pavlovian stimulus. For example, PIT occurs when the animal hears the sound produced by the predator, and then further avoids the predator's territory. PIT effects can be specific or general, depending on whether the Pavlovian stimulus influences the vigor of responding of an instrumental action previously paired with the same or different outcome as the stimulus.
Computational models of increasing complexity have been developed within the theoretical framework of associative learning. These models make various assumptions about the strength of associations between stimuli and outcomes based upon the sum total of coincidences leading up to a current state. Subsequent pairings serve to update the organism's expectation or likelihood that a particular outcome will occur given a particular event or behavior. The most influential of these models was proposed by Rescorla and Wagner Rescorla and Wagner, , which argues that the strength of the conditioned response e.
This model generates two computational signals: expected value signals i. Organisms can use these signals to indicate the magnitude of threat and guide subsequent behavior. For example, if a particular sound produces a strong expected threat signal, but the threat does not materialize, a PE signal will be generated. The PE signal will influence future behavior when the same sound is encountered, modulated by the current strength of the association.
Thus, online updating of learned associative information through these signals is a highly adaptive process that enhances survival behaviors, including actions that result in swift reduction of threat. Several studies suggest these signals and their subcomponents are represented in a number of brain regions in humans and animals, most notably the amygdala, the ventral striatum, the medial PFC, OFC, and VTA Fanselow and LeDoux, ; Buchel and Dolan, ; Elliott et al.
Until recently, appetite and aversive PE signals were assumed to be integrated and underwritten by a single system in the brain. However, recent findings suggest that aversive PEs occur in distinct areas outside the brain's dopamine driven reward system. These findings highlight the flexibility of neural circuits and the functions they can subserve, and suggest that more complex and sophisticated sets of computations can be carried out by phylogenetically older neural structures.
This flexibility may also be responsible, in part, for behavioral adaptability observed in natural ecology. Another model predicts that attention to a stimulus will decrease over time to the extent it proves to be a good predictor of reinforcement Pearce and Hall, The scenarios described are the ones that preppers are getting ready for. A wide variety of situations are described in the series, and nearly every prepper will be nodding in recognition of the events occurring. Conspiracy, beautiful conspiracy. I love a good conspiracy theory and the series is loaded with them.
They are presented in a realistic manner and not as some far-out tinfoil hat kind of thing. There are lots of little educational tidbits. The characters have to do a lot of MacGuyvering since running to Wal-Mart is not an option.
I learned several creative ideas for animal care, home fortification, and repairs on things that inevitably break down. As well, the main character, Morgan, had done a lot of reading before the collapse, so he was able to forage for food, knew some of the customs of local Native American tribes, and ways to manage the issues that send us today rushing to the store. I added some things to my shopping list based on the experiences of the characters in the books. The series is a good overview of human nature.
Children misbehave and get themselves into trouble. People get depressed because of the dramatic changes. Evil people become free to do the things they probably always wanted to, but feared arrest when times were good. Bonds between friends become more like familial ties, and a tribal mentality re-emerges. There is no electricity, no running water, no Internet, and no way to know when normalcy will be restored—if it ever will be. An avid survivalist, Morgan takes to the road with his prepper pack on his back. Now reunited with his loving wife and daughters in this follow-up to Going Home, Morgan knows that their happiness is fleeting, as the worst is yet to come.
With the help of his closest companions, Morgan fights to keeps his home secure—only to discover shocking information about the state of the nation in the process. He befriends a year-old Native American chief's grandson named Attean and learns to hunt and fish, and is eventually invited to join the tribe and move north. Some of the descriptions of native culture in this book are dated, but the underlying message is of acceptance and understanding.
Thirteen-year-old Brian Robeson is flying on a bush plane to visit his father in northern Canada for the summer, but the pilot suffers a heart attack and dies. Brian manages to crash-land the plane into a lake in the forest, and emerges with nothing but his life and a hatchet. He spends the summer surviving in the wilderness with his hatchet and becomes a fine woodsman while struggling with memories of his parents painful divorce. The book was followed by a series of sequels about Brian's various adventuring exploits which culminated in him fighting an actual bear.
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