### abstract ###
a type of emergency decision-making which has not received research attention is the police search for a lost person in a rural or wilderness area
for many such incidents  decisions concerning where to search for the lost subject are made by a planning team  each member of which assigns probabilities to the various hypotheses about where the subject might be located  including the residual hypothesis that the subject is somewhere else entirely  that is  outside of the designated search area
in the current study   NUMBER  adult males with search planning experience were asked to assign probabilities to a fictional lost person incident
it was hypothesized  according to support theory  CITATION   that subjects who first considered the five possible scenarios accounting for how the subject could have left the search area-i e   unpacked the residual hypothesis-would subsequently increase their probability estimate of the global hypothesis that the missing subject was not in the designated search area  compared to those subjects who unpacked the focal hypothesis
this hypothesis was confirmed
we also found considerable evidence for subadditivity  as most subjects estimated higher summed probabilities for the individual scenarios accounting for the focal and residual hypotheses  respectively
the potential negative consequences of such unpacking effects during a lost person incident were discussed  and possible means of mitigating such effects were described
### introduction ###
the past two decades have seen a growing interest in the manner in which emergency responders make decisions in the field
for example  klein  CITATION  and his colleagues have studied the decision-making processes of various types of emergency managers  such as fire commanders  who are required to initiate an appropriate response to their respective emergencies as early in their incidents as possible
these researchers have found that the emergency managers whom they studied rarely consider alternative options simultaneously in an analytic fashion
rather  the manager's decision making follows the pattern termed  satisficing   CITATION   in which the first satisfactory option that comes to mind is selected
the expertise of emergency managers  according to klein  CITATION   is reflected in their ability to quickly categorize an emergency according to their experience  and to imagine a scenario in which a particular course of action toward resolving the emergency could be successfully implemented
one type of emergency response not studied by klein and his associates is the police search for a person lost in a large scale rural or wilderness area  a topic which has only recently become a focus of research by behavioral scientists  CITATION
a variety of people become the targets of such searches  including hunters  hikers  anglers  and other outdoor enthusiasts  as well as children who wander away from camp or rural homes  and elderly people suffering from senile dementia  CITATION
organized searches for lost people usually come under the authority of public safety personnel such as county sheriffs  regional or state police officers  conservation officers  or park rangers
in north america  the search management system prescribed by the national association for search and rescue is nearly universally recognized as the  best practice  model for organizing a lost person incident  CITATION   and is itself an application of the incident command system endorsed by the u s federal emergency management agency for managing all emergency incidents  CITATION
below  the system will be described as it pertains to decision making processes and other cognitive variables  particularly subjective judgments of probability
a lost person incident begins with a decision that the subject of a missing person report may be spatially disoriented in a large rural environment  such as a forested area
such incidents are usually considered to be highly urgent  as factors related to health  age  weather  or natural hazards may threaten the subject's safety
in most u s states and canadian provinces  the officer who is given authority for the incident has at his or her disposal any number of resources for assistance  including other officers  personnel from other agencies  and civilian search and rescue volunteers  including field searchers  search dog handlers  and search coordinators
even before searchers arrive at the location where the search will be conducted  a search management team will be appointed for the first operational period usually  NUMBER  hours
upon arrival at the scene  the incident commander-in consultation with other members of the search management team-will set in motion routinized efforts to quickly locate the missing subject  such as tasking searchers or canine teams to track the missing person from the  place last seen  pls
as well  efforts to confine the subject to the search locale will usually be implemented  such as setting up trail blocks some distance away from the pls
after these first steps are initiated  however  the incident commander will confer with the search management team in a concerted planning session  which is strikingly unlike the  satisficing  process described by klein
environmental psychologists heth and cornell  CITATION   who have studied the decision-making processes of search managers  cogently described a typical planning session unlike most paramilitary operations  there is a surprising amount of consensual decision making
experienced search and rescue command teams believe that no one person can authoritatively state the best course of action
like the naval navigation teams described by hutchins  CITATION   there are fixed responsibilities and social hierarchies when operations are executed  but in contrast to an authoritarian and decisive control  experienced search managers seek consultation and develop their hypotheses and plans modestly with one to four others
during these discussions  the search and rescue planning team makes the search tractable by parsing the environment and developing scenarios of what likely happened to the lost person
thereafter  search management consists largely of iterative task assignments in which individuals or teams are dispatched to check these possibilities
the methodology is bayesian  the planning team will revise its priorities on the basis of field reports from the search teams  along with clues  eyewitness reports  and similar evidence uncovered during search activities  CITATION
specifically  the planning session involves identifying a primary search area in which search activities will be conducted  and then dividing this larger area into any number of smaller segments to which single search resources e g   dog teams or search crews can be tasked
once the segments are identified and drawn on the planning map  an attempt is made to prioritize the segments in order to ensure that those areas most likely to contain the missing subject are searched relatively early in the incident
prioritization is accomplished by requiring the search planners to assign estimates of probability to each of the segments  termed  probability of area  poa
as well  the methodology involves assigning some nontrivial probability to the  rest of the world  row  that is  all of the area outside of the designated search area  which will likely not be searched during that operational period  CITATION
the individual probability judgments are then combined and averaged  yielding a planning poa that reflects the consensual probabilities that the subject may be located within each segment as well as the row
as mentioned in the quote above  the methodology is bayesian  in that the initial subjective probabilities are recomputed according to bayes theorem as segments are searched and the lost person is not located see appendix a
because the row  by definition  does not receive search assignments  it will necessarily grow larger in poa as the search proceeds and negative information decreases poa in various segments within the search area
indeed  search coordinators are advised to monitor the poa of the  rest of the world   particularly with respect to decisions about expanding the search  which is accomplished by partialing out new segments formerly outside of the designated search area  CITATION
as noted by heth and cornell  CITATION   the process of developing a search plan resembles the interlocking cognitive efforts contributed by members of a navigation crew of a u s navy ship as described by hutchins  CITATION  in his book  cognition in the wild
hutchins applied the term  distributed cognition  to describe such mutual and complementary efforts of individual specialists using a host of cognitive  artifacts  such as maps  charts  electronic instruments  and computers
similarly  fischhoff and johnson  CITATION  used the term  distributed decision-making  to refer specifically to command-and-control type operations in which decisions are made by two or more individuals
although during search operations numerous artifacts may be employed  such as maps  software  statistical data  and lost person behavior  profiles   CITATION   the emphasis in this article will be on the subjective probabilities initially assigned to the search area and which become the starting point for the subsequent bayesian computations made as the search proceeds
as stated earlier  the methodology for prioritizing the search area requires planners to make subjective estimates of probability for each segment in the search area  plus the row
it is assumed that such judgments are based on the planners' sar experience and acquired expertise  plus reference to actuarial data tabulated from previous lost person incidents  such as how far from the pls various types of lost people tend to travel before being located  CITATION
unfortunately  much research on decision processes would appear to cast doubt on the ability of planners to make valid probability judgments  as the ability to render unbiased assessments of probability for uncertain events has been challenged by tversky  and  koehler's  CITATION  support theory  CITATION
briefly  support theory maintains that subjective probability judgments are based not on the likelihood of events themselves  but on descriptions of events
thus  the same event may be seen as more or less likely depending on the manner in which it is described to those making the judgments
for example  people estimate significantly higher chances of dying from heart disease  cancer  or other natural causes  than simply from any natural cause  CITATION
this unpacking effect is said to occur whenever people are asked to consider the disjoint components of an uncertain event that is  various possibilities that can cause the event rather than merely the event itself
in other words  the more explicitly an event is described  the more likely it will be judged to occur
various explanations for unpacking have been proposed  including the tendency for an explicit inclusion of specific causes of an effect to increase confidence in that cause  CITATION   or to remind people of possibilities they might have overlooked  CITATION
a side effect of unpacking is subadditivity
according to tversky and koehler  CITATION   when people are asked to make a global judgment  such as the probability of dying from an unnatural cause  they tend to base their judgments on a representative or typical case  without necessarily delineating  in this example  the possible types of unnatural causes
however  unpacking the event to be judged e g   homicide  fatal accident  drowning not only leads to higher estimates of probability  but frequently in total probabilities greater than  NUMBER  percent   CITATION
the term subadditivity therefore refers to the fact that probability judgments of the globally described event are less than the sum of that assigned to the unpacked version of the event
another important consideration in support theory pertains to those occasions when people judge the relative probabilities of two or more mutually exclusive hypotheses
for example  if there are three suspects in a crime  a  b  and c  the hypothesis that a is the culprit and the associated probability that a did it is termed the focal hypothesis  while the possibility that someone other than a is guilty b  c  or some unknown x is called the residual hypothesis
in this case  the set of possibilities-either a or not-a symbolized as   x NUMBER  -is discrete that is  either hypothesis must necessarily be true
in support theory  each hypothesis under consideration will have varying degrees of support  each depending on the manner in which the hypothesis is described for example  whether or not it is unpacked
when comparing the relative probabilities of the focal and residual hypotheses  support for the former s a  will decrease the estimated probability for the latter s   x NUMBER     as seen in the formula    where pa   x NUMBER   refers to the probability that a rather than   x NUMBER   is true
bringing the discussion back to the search and rescue planning task  we can describe the hypothesis that the missing subject is in the designated search area as the focal hypothesis  while the possibility that he or she is somewhere else-the row-as the residual hypothesis
a typical application of the poa methodology described earlier  using the support theory terminology  is as such
after some discussion  the individual planners proceed to individually unpack the search area into smaller segments all of which represent separate hypotheses about where the subject might be  and finally to allocate some probability to the residual hypothesis  that is  that the person is in none of those segments
at this point  we can begin to form our own hypotheses as to why this methodology sometimes fails
according to hill  CITATION   the single most common reason why a lost person is not found in a reasonable period of time is that the victim had traveled out of the designated search area and that search planners had not extended the search into the row soon enough
a similar problem is apparently encountered by the u s coast guard in their conduct of maritime sar  such as searching for missing vessels at sea
described as  scenario lock   it is said to occur  when planners become fixated on a particularscenario to the exclusion of all others   CITATION
it is possible  if not indeed likely  that planners in these emergency situations are experiencing unpacking effects which tend to keep them unreasonably  locked  to their focal hypotheses
in other words  in considering all the many possibilities that could account for the missing person or vessel at sea to be in any of the search segments  planners estimate a consensus poa that is inflated for the focal hypothesis that the target is in the designated search area while underestimated for the residual hypothesis that the target is somewhere else
even if a bayesian procedure is used for reevaluating poa as the search proceeds  the eventual decision to reject the focal hypothesis and to start extending the search into the row is delayed  to the detriment of the lost person's safety
for example  in the application of the bayesian formula as applied to sar see appendix a  poa's are updated each time a segment is searched and the subject is not found
with each iteration  the poa of the row grows slightly larger
