document: maslow 's hierarchy of needs has been a well - known theory since abraham maslow proposed it in 1943   and in his book motivation and personality in 1954 , in which he proposed that human needs can be portrayed in the shape of a pyramid , with the most fundamental levels of needs at the bottom . from bottom to the top are the needs : physiological needs , safety , belongingness and love , esteem , and self - actualization . 
   physiological needs are the physical requirements for the survival of individual and the animal kind , such as food and sex , and safety needs are personal security , financial security , and health and well - being . 
   maslow proposed that if the physiological needs are relatively satisfied , there then emerges a new set of needs , which may be categorized roughly as the safety needs . 
   the organism may be wholly dominated by them , which may serve as the almost exclusive organizers of behavior , recruiting all the capacities of the organism in their service , and we may then fairly describe the whole organism as a safety - seeking mechanism . 
   but maslow also found that  practically everything looks less important than safety , even sometimes the physiological needs which being satisfied , are now underestimated . 
   safety needs are personal security , financial security , and health and well - being , which are more fundamental than physiological needs ( figure 1 ) . for example , the deer can not eat ( physiological needs ) on the wild prairie when the wolves chase them ( safety ) . 
   let me take one example from cosmides and tooby ( 2000 ) , who propose that the emotions serve to regulate behavior . 
   he wrote about fear like this :  imagine walking alone at night and hearing some rustling in the brush . 
   your energies are aroused to be ready for action , you become acutely aware of sounds that could indicate that you are being stalked , the threshold for detecting movements is lowered , you no longer feel pangs of hunger , attracting a mate is the farthest thing from your mind .  . 
   whether physiological needs or safety needs are more important will affect our opinions about mental disorders , for example , freud proposed libido ( physiological needs ) more important . 
   safety needs can block physiological needs ; the classical example is miller 's avoidance and approach experiments ( figure 2 ) . in 1961 , 
   neal miller used behavioral measures to assess motivational disposition in rodents ( figure 2 ) . 
   as the animal moves closer to the potential reward ( e.g. , food ) , the force exerted to obtain the reward increases . 
   similarly illustrated is the avoidance : the force the animal exerted to avoid the aversive stimulus ( a shock ) also increases as the animal comes closer , and furthermore , the slope of the avoidance gradient tended to be steeper than that of approach . 
   later experiments by ito found that the organisms tend to be more sensitive to the threatening information and generally process such information faster than the rewarding information . 
   he called this phenomenon negativity bias and attributed it as a protective strategy through evolution , since even a single failure to respond adaptively to a survival threat may preclude passing on genetic information . 
   he found that  as a potential treat looms , the adaptive response of the brain is to amplify these threats and initiate appropriate behavioral responses , such as fleeing , freezing , or attacking .  and he found that the negativity bias can be seen across all levels of the neuraxial organization . 
   these data support the notion that safety needs are faster and more fundamental than hedonic needs . 
   maslow thought adults usually inhibit the reaction for safety needs , so he used infants as an example and found that the child 's need for safety is his preference for some kind of undisrupted routine or rhythm . 
   maslow mentioned ,  he seems to want a predictable , orderly world . for instance , 
   injustice , or inconsistency in the parents seems to make a child feel anxious and unsafe . 
   this attitude may be not so much because of the injustices per se or any particular pains involved , but rather because this treatment threatens to make the world look unreliable , or unsafe , or unpredictable .  . 
   maslow also mentioned ,  confronting the average child with new , unfamiliar , strange , unmanageable stimuli or situations will too frequently elicit the danger or terror reactions . 
   this is consistent with the behaviorists , who propose that behavior is a process - form  stimulus - reaction  , while cognition scientists extend it to  stimulus - opinion - reaction . 
   is stimulus that has the hedonic value , which fits into our personal physiological needs . 
   and it also has another feature : happening in an expected way , or unexpected way , which is related to threat and can be called safety value . 
   we draw these two features of stressful events in two dimensions : hedonic value and safety value ( figure 1 ) . 
   the safety value has nothing to do with the hedonic value , for both the liked things and disliked things can induce unsafety . 
   for example , we worry about losing the liked things and also worry about getting the disliked things ; and we also will not be angry if we lose the good thing as expected and also get the disliked thing as expected . 
   even though it is something you liked , if it is unexpected , you still feel afraid and angry . therefore the safety is related to unexpectancy 
   . one feature of the safety need induced emotion is the rapid detection of potential threats and can initiate appropriate approach / avoidance behaviors . 
   prediction error . 
   the studies were done from electrophysiological recordings of dopamine neurons in awake , behaving monkey in schultz 's lab . 
   these phased activation does not discriminate different types of rewarding stimuli . and it is quite unexpected that the reward delivery will not elicit dopamine neuron firing , once the animal has learned the stimulus and reward association . 
   therefore , dopamine neurons are related to expectation about external stimulus rewarding , especially when it is uncertain or prediction error [ 6 , 7 ] . 
   the studies of emotions have been expanded exponentially by two prominent researchers : magda arnold and richard lazarus , who proposed appraisal theory . 
   appraisal theory states that emotions result from people 's interpretations and explanation of their circumstances . in the structural model of appraisal theory , 
   lazarus borrowed the concept of appraisal from arnold and elaborated the concept as a key factor for emotions : emotional processes depend on the predictability of the stressful events . 
   he distinguishes two basic forms of appraisal , primary and secondary appraisal , and he proposed that the primary appraisal and its induced emotions are a faster activating , automatic process , which is similar to the safety need . 
   indeed , lazarus distinguishes three types of stressful events : harm , threat , and challenge , which are related to primary appraisal . 
   the secondary appraisal is concerned with coping options , which include blame or credit , coping potential , and future expectations . 
   it seems that the primary appraisal is related to fear and the secondary is related to anger ( figure 3 ) . 
   lazarus mentioned that if a person appraises a situation as motivationally relevant , motivationally incongruent and also holds a person other than himself accountable , the individual would most likely experience anger in response to the situation . process model of the appraisal theory is more accurate to explain the safety needs , for personal safety , which are related to the  unexpected ways of stimulus occurring . 
   the process model proposed two main appraisal processes : perceptual stimuli and associative processing and reasoning . 
   perceptual stimuli are what the individual picks up from his surroundings , such as sensation of pain or pleasure . 
   then , the individual performs two main appraisal processes : associative processing , which is memory based , and reasoning , which is a slower and more deliberate process that involves logical thinking about the stimulus . 
   for example , when you meet a car that quickly passes and stops before you , you will be firstly scared and then blame the car . 
   let us take another example from izard 's paper ,  when rafe was hit from the back by a wheel chair , the first reaction of him was scared and angry , and showed angry expression and clenched fist . 
   but after he turned back to see rebecca , a person with hemiplegia whose wheelchair had gone out of control and cause her to crash into rafe . 
   so when something unexpected occurs , you will first evaluate its threat ( fear / anger ) and next evaluate its hedonic value ( happy / sad ) ( figure 3 ) . 
   similar emotional flow happens in our lives all the time : everything in our lives is normally calm as expected ; but you will first feel scared ( fear ) when something unexpected occurs , and then you will blame ( anger ) the un - expectancy after fear is gone . and 
   afterwards you might feel happy after successfully coping with the stressful events or feel sad if you failed to cope with them . finally , the stressful events go away , and people calm down . 
   this kind of emotional flow , big or small , long or short , constitutes our everyday emotions . 
   so fear - anger - happiness - sadness - calm might constitute the rainbow of emotions or emotional flow in our everyday life . 
   the amygdala has been proved to be the neural basis for fear , and it is also recognized as the neural basis for stress elicited fear and anxiety [ 12 , 13 ] . 
   in addition , electrical stimulation of the amygdala promotes autonomous reactions and stress - like behavioral , whereas amygdala ablation induced a marked tameness increase , motivation loss , and fear decrease to aversive stimuli [ 14 , 15 ] . 
   amygdala is one of the most important limbic structures that link to fear , which was first suggested by klver & bucy in 1937 , who demonstrated that the lesion of the medial temporal lobe resulted in a wide range of odd behaviors , such as approaching normally to fearful objects . 
   and about 20 years later , weiskrantz ( 1956 ) found that it is the amygdala whose impairment resulted in the odd behaviors , which are called klver and bucy syndrome . 
   ledoux puts amygdala as the emotional computer to work out the emotional significance of stimuli . 
   he demonstrated two neural pathways of sensory information from the thalamus to the cortex : ( 1 ) a slow - acting  thalamus - to - cortex circuit ,  whose function is to analyze sensory information in detail , and ( 2 ) a fast - acting  thalamus - amygdala circuit ,  whose major function is to analyze simple stimulus features , which bypass the cortex . 
   these two pathways possibly underlie the two evaluation systems : the fast one for the fear / anger and the slow one for hedonic . 
   other reports , such as findings from ohman and soares ( 1994 ) also support a fast - acting system for threat detection that involves only minimal cortical processing [ 19 , 20 ] . 
   ( 2001 ) also reported a patient whose primary visual cortex was impaired and therefore showed no conscious visual perception but showed significant fearful reports . 
   in all , the fast - acting thalamus - amygdala circuit is important for our ancient ancestors to rapidly recognize dangers to help with survival . 
   it is an evolutionary adaptation for our ancestors to better cope with the unexpected environment with the fast activing thalamus - amygdala circuit . 
   in addition to amygdala , the ne / lc system is important to direct behaviors of the animal to cope with the dangerous environment , and the well - known function of ne / lc system is to induce  fight or flight  behaviors . take a deer in the wild as an example . 
   when a deer meets a lion , the reaction of the deer is flight ( fear ) , while the reaction of a lion is fight ( anger ) . 
   so the emotion fear and anger might also be derived from the same neurotransmitter ne and the same stressful event ( figure 4 ) . 
   ne is released from the locus coeruleus ( lc ) in the brain to keep the brain alert , which has been described as increasing the  signal to noise  of the sensory inputs . 
   lc has been reported to be activated at stressful events : increased lc neuron firings were observed at visual threat . and 
   lc sends projections to amygdala , which is the most important limbic structure that links to fear . 
   therefore , amygdala and ne / lc system might constitute the neural structure for safety needs . 
   our ancestors navigating rich environments had to face very complicated environments , with many forms of uncertainties . 
   so they evolved an adaptive mechanism to first do a safety check for everything around them . 
   if it would happen in an anticipated way , they will feel calm ; instead if something happened surprisingly , they will be scared and angry 
   . therefore , fear and anger are due to things happening in an unexpected way ( figure 4 ) . of note , the unexpectancy will also increase the tension of hedonic emotions . with the same kind of hedonic stimulus , 
   if it comes in an unexpected way , people will feel excited ; instead , people will feel happy . 
   one reason for the clearer appearance of the threat or danger reaction in infants , is that they do not inhibit this reaction at all , whereas adults in our society have been taught to inhibit it at all costs . 
   thus even when adults do feel their safety to be threatened we may not be able to see this on the surface . 
   infants will react in a total fashion  in infants we can also see a much more direct reaction to bodily illnesses of various kinds  for instance , vomiting , colic or other sharp pains .  . 
   even the adults can inhibit our reactions , they still can react in some mental disorders . 
   maslow wrote ,  some neurotic adults in our society are , in many ways , like the unsafe child in their desire for safety , although in the former it takes on a somewhat special appearance . 
   their reaction is often to unknown , psychological dangers in a world that is perceived to be hostile , overwhelming and threatening . 
   the neurotic individual may be described in a slightly different way with some usefulness as a grown - up person who retains his childish attitude toward the world . 
   this is to say , a neurotic adult may be said to behave as if he were actually afraid of a spanking , or of his mother 's disapproval , or of being abandoned by his parents , or having his food taken away from him . 
   it is as if his childish attitude of fear and threat reaction to a dangerous world had gone underground , and untouched by the growing up and learning processes , were now ready to be called out by any stimulus that would make a child feel endangered and threatened . 
   fear - phobia . 
   if something happens surprisingly , people will be scared and angry ; and if it would happen in an anticipated way , they will feel calm . 
   so for the phobia patients , their problems might be that they can not successfully accomplish the emotional flow ( fear - anger - happiness - sadness - calm ) . 
   the best way to remove fear is anger , these patients are too timid to show anger , so their emotions are checked at emotional flowing from fear to anger . 
   therefore , anger might be the best treatment for these patients and ne is the neural substrate for them . 
   depression is characterized by unrelenting sadness accompanied by an inability to derive pleasure from positively hedonic situations . 
   therefore , depression might be related to the primary appraisal , the worrying about safety instead of physiological satisfaction . 
   indeed , excessive self - blame and feeling worthless are symptoms of major depression episodes across cultures , which is similar to lazarus 's secondary appraisal . 
   so the depressed patients have problems with anger or with coping appraisal or their problem is due to inability to cope with the unsafe stressful situation and showed inward anger . 
   the difference between fear and anger is the direction of the behavior : fear is to throw oneself away from the stimulus and anger is to throw the stimulus away . 
   for these patients , they do not have the ability to throw the outside stimulus due to repeated helplessness , they want to kill themselves . 
   safety needs are the most fundamental needs for the human kind , which include personal security , financial security , and health and well - being . 
   safety is the major reason for mental disorders , such as anxiety , phobia , depression , and ptsd . 
   the neural basis for safety is amygdala and lc / ne system , which can be regarded as a  safety circuitry ,  whose major behavior function is  fight or flight  and  fear and anger  emotions , or conditioned learning for these emotions . fear and anger are due to the safety needs , while joy and sadness are due to the physiological needs , which should come after safety needs in maslow 's hierarchy of needs . 
   fear and anger are two sides of one sword , for they will act in different directions : fear is to flight away from the danger and anger is to fight the danger away . 
   they are all due to the stressful events : normally everything is as expected , and life is calm . 
   when something unexpected happens , the individuals first feel scared and then blame the unexpectancy ; this is the first safety check . 
   afterwards the individual will have a hedonic need to see if it fits their personal needs and get the happy or sad emotions . 
   finally , everything comes to an end , and people return to calmness or miss the lost things and worry for the uncertain bad things . 
   so the emotional rainbow ( or emotion flow ) fear - anger - happiness - sadness - missing constitutes our emotions in everyday life .
summary: safety first ,  we say these words almost every day , but we all take this for granted for what maslow proposed in his famous theory of hierarchy of needs : safety needs come second to physiological needs . here 
   we propose that safety needs come before physiological needs . 
   safety needs are personal security , financial security , and health and well - being , which are more fundamental than physiological needs . 
   safety worrying is the major reason for mental disorders , such as anxiety , phobia , depression , and ptsd . 
   the neural basis for safety is amygdala , lc / ne system , and corticotrophin - releasing hormone system , which can be regarded as a  safety circuitry ,  whose major behavior function is  fight or flight  and  fear and anger 
   emotions . 
   this is similar to the appraisal theory for emotions : fear is due to the primary appraisal , which is related to safety of individual , while anger is due to secondary appraisal , which is related to coping with the unsafe situations . if coping is good , the individual will be happy ; if coping failed , the individual will be sad or depressed .