Dunedin film-maker Phil Davison loves a good fright.
''I like watching horror films. I also like making them. Hence I drive my wife crazy when we are watching one because I'm always stopping and rewinding certain sections.''
Davison, whose CV includes 2013 feature Ghost TV, Kung Fu Vampire Killers and Belief, has also lectured in film at the University of Otago, Otago Polytechnic and the Southern Institute of Technology.
He admits his dissection of the innards of a good number of horror films has probably ruined his students' enjoyment of them.
Yet ensuring an audience experiences that feeling of creeping dread does require no small measure of craft and, significantly, context.
''Someone walking down a corridor is not inherently scary, but walking down a corridor in a spooky house is,'' says Davison, who shot Ghost TV at the former Seacliff psychiatric asylum.
Empathy is important, too.
''We respond to facial expressions. A close-up of an actor looking terrified stimulates a sympathetic response.
''At heart we are pack animals, evolved from small groups of hunter-gatherers. One of the skills we have acquired is the ability to recognise how people are feeling. If we are going to work together as a group to hunt a mammoth, we will survive better if we can respond to each other.
''This leads us to respond empathetically with characters in a movie when we see them look scared. This is also why psychopaths or sociopaths are scary: they don't respond to the social cues as we expect.''
And the best way to build an audience's empathy with characters? Tell a good story.
''The more problems a character has and the more vulnerable they are, the more we empathise with them,'' Davison explains.
''What I sometimes see with my students' films is a bunch of scary events, one after the other, but that actually gets boring. You need to have suspense as that gets you involved in the story more.''
Davison points to acclaimed British director Alfred Hitchcock's theory of suspense: ''If two people are sitting at a table and the building is destroyed by a huge explosion, that is of limited value.
''That slow-burning suspense is in the original version of [1973 blockbuster] The Exorcist. Not much happens in the first half of that movie but you can't stop watching.''
In regards to horror film methodology, Davison even raises the spectre of Greek philosopher Aristotle: ''His theory about drama is that we don't want to experience certain emotions in real life but we need them, so by experiencing them vicariously through entertainment we purge them.''
People enjoy feeling scared and seek the feeling out precisely because they know they are in no real danger, David Rudd, dean of the College of Social and Behavioural Science at the University of Utah, writes on the website Life's Little Mysteries.
''They understand the real risk of these activities is marginal, and because of this underlying awareness, they experience excitement rather than actual fear,'' he explains.
This is why people enjoy going on terrifying amusement park rides, pay money to be frightened by ghouls/zombies/demons in haunted house-type attractions or go on a date to a thriller flick.
Karl Iremonger, a lecturer in neuroendocrinology in the department of physiology at the Otago School of Medical Sciences, University of Otago, says a fright (as may be caused by a zombie jumping out of a cupboard to try to eat you) evokes what is known as the stress response.
''The stress response has both a `fast' and a `slow' component, both of which are controlled by the brain.
''The fast response involves the release of adrenaline/noradrenaline from nerve endings and the adrenal gland,'' Dr Iremonger explains.
''The slow response involves the release of the stress hormone cortisol, also from the adrenal gland. The release of these molecules increases blood pressure, heart rate and respiration, and mobilises fuel for the body.
''All of these responses better enable you to flee from the zombies or else fight them off, i.e. the fight or flight response.
''Stress also induces the release of neurotransmitters within the brain, including noradrenaline and endogenous opioids. These neurotransmitters increase arousal and inhibit pain responses, which also facilitate survival when faced with a life-threatening stress.''
Brian Hyland, head of the department of physiology, Otago School of Medical Sciences, University of Otago, notes that the brain systems that monitor and respond to threat and generate fear are closely connected to dopamine pathways, which detect and ''code'' events that predict good outcomes and generate feelings of pleasure.
''With respect to dopamine reward systems, one obvious possibility for the crossover from fear to reward is that stopping something bad is in itself rewarding.
''Some very early theories of motivation actually proposed that it was more about seeking to reduce bad feelings (i.e. pleasure from food was due to reduction of a bad feeling, hunger); whereas latterly more emphasis has been placed on the idea that we act to obtain pleasure (we seek out food because it tastes good, etc).
''Now we know that rather than one or other of these theories being `the one', probably both kinds of drive are important, in different situations,'' Prof Hyland says.
''Simply put, the idea of gaining pleasure from pain could result from the close wiring of the systems, and the fact that release from one (pain) triggers pleasure.
''It would therefore be possible for the system to learn that pain preceded pleasure, and thus the pain could become rewarding in itself, because of it predicting a good outcome down the track.''
