***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective To examine the prevalence rate , impairment , comorbidity , course of illness and determinants of eight specific phobia variants : animals ( animal subtype ) ; heights , water , storms ( natural environment subtype ) ; flying , enclosed spaces , being alone ( situational subtype ) ; and blood/injury ( blood/injury subtype ) . Method Data were obtained from the Netherl and s Mental Health Survey and Incidence Study , a prospect i ve study in the Dutch general population aged 18–65 ( N = 7,076 ) . Results The most prevalent condition was specific phobia with a fear of heights ( 4.9 % ) . On all parameters except duration , specific phobia with a fear of being alone emerged as the most severe condition . Phobias with fear of enclosed spaces and phobias with fear of blood showed a slightly greater likelihood of impairment , comorbidity and personality problems than phobias with fear of animals , heights , water or storms . Conclusion The situational and blood/injury phobia subtypes appear to be a more significant index for impairments and for comorbid psychiatric disorders than the animal and natural environment phobia subtypes Experimental tests of the preparedness theory of phobias have found that skin conductance responses ( SCRs ) conditioned to fear-relevant stimuli ( e.g. pictures of snakes and spiders ) exhibit more resistance to extinction than those conditioned to fear-irrelevant stimuli ( e.g. pictures of flowers and geometric figures ) . However , there are no published replications of this phenomenon outside the laboratories of Ohman and his associates . The experiment reported here failed to replicate previous findings insofar as SCRs established to fear-relevant stimuli were no more resistant to extinction than those established to fear-irrelevant stimuli . Indeed , ‘ preparedness ’ effects were absent even in Ss who reported prior fear of snakes and spiders . Correlational analyses indicated that the strength of conditioning was the only predictor of resistance to extinction to fear-relevant stimuli — a finding consistent with general process-learning theories The effects of conditioned stimulus ( CS ) pre-exposure and fear- relevance of the CS on human Pavlovian electrodermal conditioning were investigated . A differential delayed conditioning paradigm was used with a CS-unconditioned stimulus ( US ; shock ) interval of 8 s. In Experiment 1 , 64 subjects were r and omized into four groups , two of which received fear-relevant stimuli and the other two fear-irrelevant stimuli . Half of the subjects were pre-exposed to the to-be-CSs and the other half to two not-to-be-CSs , with 15 exposure of each stimulus . During acquisition , subjects received 8 reinforced and 8 nonreinforced CS+ and CS- trials , and during the extinction phase 15 nonreinforced trials of each CS . Pre-exposure to the to-be-CSs retarded conditioning for the first and second interval anticipatory responses ( FIRs and SIRs ) ; that is , a latent inhibition effect was demonstrated , although the results for the FIR were inconclusive . The expected effects of fear- relevance were not revealed . Experiment 2 addressed the question whether the long pre-exposure period interfered with the frequently observed " preparedness effect " of higher resistance to extinction to fear-relevant stimuli . The design was similar to that of Experiment 1 , but for half of the subjects the acquisition phase was initiated immediately after a short rest period , and for the other half acquisition started after an extended rest period , equal to the duration of the pre-exposure phase in Experiment 1 . Twenty extinction trials of each CS were presented . A reliable difference in arousal in terms of spontaneous fluctuations was produced by the rest periods , but although differential conditioning was observed , no effect of fear- relevance was seen during extinction 
    Output:
    
Thus , the body of evidence suggests that preparedness theory does not explain the origin of specific phobias