=Paper=
{{Paper
|id=None
|storemode=property
|title=The effect of time pressure ad task completion on the occurrence of cognitive lockup
|pdfUrl=https://ceur-ws.org/Vol-696/paper10.pdf
|volume=Vol-696
}}
==The effect of time pressure ad task completion on the occurrence of cognitive lockup==
https://ceur-ws.org/Vol-696/paper10.pdf
CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
The effect of time pressure and task completion on the occurrence of cognitive
lockup
Ernestina J. A. Schreuder (elianeschreuder@hotmail.com)
TNO Human Factors Research Institute, kampweg 5
Soesterberg, 3769 ZG The Netherlands
University of Utrecht,
Department of Psychology, Heidelberglaan 1,
Utrecht 3584 CS The Netherlands
Tina Mioch (tina.mioch@tno.nl)
TNO Human Factors Research Institute, kampweg 5
Soesterberg, 3769 ZG The Netherlands
Abstract reluctant to switch to another task, even if that task has a
higher priority (Neerincx, 2003). The following flight
Prior studies have suggested that time pressure and task incident illustrates the possible consequences of cognitive
completion play a role in the occurrence of cognitive lockup. lockup. During landing, the pilot of flight 401 of Eastern
However, supportive evidence is only partial. In this study, we Air Lines (1973) was warned about a problem with the
conducted an experiment to investigate how both time pressure
and task completion influence the occurrence of cognitive
landing gear. To win time, the pilot canceled the landing,
lockup, in order to better understand situations that could set the plane in the autopilot mode and started solving the
trigger the phenomenon. We found that if people have almost problem with the landing gear. This problem fully
completed a task, the probability for cognitive lockup increases. occupied the pilot and multiple warnings about a
We also found that the probability for cognitive lockup decreasing altitude (a low-altitude alarm, a remark of the
decreases, when people execute tasks for the second time. There air-traffic controller) were ignored. As a consequence, the
was no effect of time pressure or an interaction effect found plane crashed, resulting in the death of most people on
between task completion and time pressure. The results provide board.
further support for the explanation that cognitive lockup up is Experimental studies exist where cognitive
the result of a decision making bias and that this bias could be
triggered by the perception that a task is almost complete.
lockup was manifested in the data (Moray and Rotenberg,
1989; Kerstholt, Passenier, Houttuin and Schuffel, 1996),
however, an explanation for the occurrence of the
Introduction phenomenon was not given. The following literature
overview provides accounts for the occurrence of the
This study is about an inescapable part of action, phenomenon.
something all human beings experience to a greater or
lesser extent: human error. Human errors can happen in Reduced situational awareness as trigger for
everyday situations with only limited consequences.
cognitive lockup
However, errors can also happen in high-performance
environments like in aviation, where they can have A popular concept (Meij, 2004) is the idea that a reduced
tremendous effects and be life threatening. For instance, situational awareness (SA) might cause cognitive lockup.
when pilots forget to enable their landing gear when Kerstholt and Passenier (2000) argued that if operators
landing and as a result crash. Hence, it is important to become less aware of the actual situation, for instance,
investigate why human errors in aviation are made and due to automation, they may not be able to understand the
how errors can be avoided. links between the various subsystems they have to
In the past, several cognitive explanations and control. If operators lack the knowledge of the underlying
theories have been proposed to understand why pilots systems cognitive lockup is more likely to occur.
deviate from normative activities (e.g. Wickens and Kerstholt and Passenier suggested that knowledge of the
Hollands, 2000; Dekker, 2003). The European project underlying systems is important in order to increase SA
HUMAN (www.human.aero) strives to pave a way for and prevent cognitive lockup.
making this knowledge readily available to designers of Jones and Endsley (1996) investigated flight
new cockpit systems, in order to be able to design accidents caused by a reduced SA. They found that a
cockpits that prevent pilots from making errors. They great part of the flight accidents was due to a failure to
identified cognitive lockup to be among the most relevant monitor or observe relevant data that were clearly present
mechanisms for modern and future cockpit human in the situation. This type of accidents could also have
machine interfaces. Cognitive lockup is the tendency to been the result of cognitive lockup, as important tasks
deal with disturbances sequentially (Moray and were that were triggered while dealing with another
Rotenberg, 1989). As a result of cognitive lockup problem, were ignored. Therefore, it could be suggested
operators are inclined to focus on the current task and are that cognitive lockup is triggered by a failure to monitor
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
the environment. However, Meij (2004) found in his that people have flexible control over the course of
study on cognitive lockup, that cognitive lockup could secondary task processing stages. They argued that the
not be explained by a neglect of environment. Hence, a fact that switching costs arise is not due to a cognitive
reduced SA and specifically the failure to monitor the bottleneck but is rather optional and strategic. The
environment seem not to be an underlying mechanism of reconfiguration to another task takes time and thus,
cognitive lockup. switching costs arise.
Meij (2004) proposed that people might decide
High cognitive workload as explanation for to stick to their current task because the switching costs
cognitive lockup that accompany task switching are perceived as too high.
Cognitive workload refers to the information processing He found that cognitive lockup was reduced when it was
demands imposed by the performance of cognitive tasks obvious that the benefits of a switch to another task were
(Johnson and Proctor, 2004). In order to predict the higher than the costs of a switch. He argued that the
cognitive load of a specific task, Neerincx (2003) participants were biased in their decision-making process,
developed the cognitive task load (CTL) theory. This as the costs of switching to another task had to be
theory proposed three underlying factors of cognitive task disproportionally low before participants decided to
load: (1) time occupied, (2) number of task set switches, abandon the current task. Although the results showed
which is the number of active tasks in execution or that the tendency for cognitive lockup was considerably
planned to do, and (3) level of information processing. reduced when the costs to switch were low, the tendency
Neerincx (2003) suggested that cognitive lockup would for cognitive lockup was still present. Therefore, Meij
occur when time occupied and the number of task set suggested that besides switching costs, other factors that
switches are high. Grootjen, Neerincx and Veltman, trigger cognitive lockup are involved.
(2006) conducted experiments in order to validate the
CTL theory. In these real-life experiments participants A decision making bias as trigger for cognitive
had to deal with emergencies that appeared on a ship. lockup
They found that when all three factors were high people A decision making bias refers to the fact that decision
experienced cognitive overload; they did not know what making can be influenced by a prejudice or 'one-sided'
to do. However, no evidence of cognitive lockup was perspective. A bias can be unconscious or conscious in
found. Furthermore, Grootjen et al. (2006) found that in awareness. Meij (2004) believed that cognitive lockup is
the overload situation, participants switched much more due to a decision making bias. When dealing with a task
between tasks than in the optimal strategy. This result is people decide to switch or not to switch to another task
likely to indicate that a high workload does not influence when triggered. This decision might be biased due to for
the occurrence of cognitive lockup. instance a misperception of expected benefits. As a
In the same vein, Meij (2004) investigated result, people could decide not to deal with an additional
whether a lack of cognitive resources could be an more urgent task until the ongoing task is dealt with. To
explanation for cognitive lockup. He argued that tasks find out whether cognitive lockup results from a decision
that require a more complex diagnosis process are making bias, Meij (2004) conducted several experiments
expected to demand more cognitive resources and thus with a fire control task. In this task participants had to
cause a higher cognitive workload and might cause extinguish fires on a ship in a computer simulation. When
cognitive lockup. He found, however, that the level of a fire appeared the participants had to detect the fire by
complexity of information processing did not affect the clicking on the fire. After detection, participants had to
degree of cognitive lockup. Hence, Meij (2004) indicated extinguish the fire by selecting the right treatment. He
that cognitive lockup is not caused by the fact that people used this task because in his first experiment he
lack the cognitive resources to switch. This result successfully demonstrated that cognitive lockup could be
underscores that it is likely that a high workload does not found using this task.
cause cognitive lockup. Meij (2004) proposed that both task completion
and prior investments, such as money, time and effort,
Too high switching costs as explanation for might bias the decision to switch to another task. Meij
cognitive lockup found that when prior investments are high and the task
When people switch between tasks, people are slower was near completion (high task completion), the
and less accurate than when they repeat tasks (Jersild, probability for cognitive lockup increased. Remarkably,
1927; Monsell, 2003) and these switching costs have he also found that when prior investments are high and
been attributed to a variety of processes. Pashler (1994) task completion is low, people have the tendency to
suggested that switching costs arise because of a abandon their task. Hence, the probability for cognitive
cognitive bottleneck to process or select information. lockup decreased. Meij argued that in the high prior
This means that when a cognitive process is devoted to a investments condition perceived time pressure may be
primary task, this process can not start for a second task. higher than in the low prior investments condition. This
This second task has to wait, yielding switching costs. is because the available time in relation to invested time
Schumacher (1999) and Meyer and Kieras (1997a, is lower in the high prior investments condition.
1997b) argued that switching costs arise due to an Therefore, he attributed the effect of prior investments to
executive control mechanism. They proposed a class of the perception of time pressure. He suggested that when
adaptive executive control models in which it is assumed time pressure is perceived as high and the ongoing task is
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
almost completed, people are more likely to stick to the and tend to employ more effortful systematic information
ongoing task than in situations where time pressure is processing that gives serious considerations to all
high and the ongoing task needs considerable activities in possible alternative solutions for a task (Kelly and
order to complete it. Thus, the results of Meij’s Loving, 2004). Interestingly, DeDonno and Demaree
experiments (2004) are likely to indicate that cognitive (2008) found that the mere perception of time pressure as
lockup is due to a decision making bias. This decision well as real time pressure impair performance.
making bias seems to be triggered when time pressure Thus, time pressure can trigger heuristic information
and task completion are high. processing that make people focus on an ongoing task
(van der Kleij, 2009; De Dreu, 2003; Durham et al.,
Current study: the effect of time pressure and 2000; Karau and Kelly, 1992; Kelly and Loving, 2004).
task completion on cognitive lockup As a result, time pressure might influence the tendency to
From the literature overview it seems that cognitive stick to the ongoing task and influence the occurrence of
lockup is the result of a biased (un)conscious decision to cognitive lockup. However, in situations where time
1
focus on the current task and ignore others. Time pressure was high Grootjen et al. (2006) found a high
pressure and task completion seem to influence this cognitive workload, but they found no relation to
biased decision. The aim of this study is to investigate cognitive lockup. Therefore, we expect that the effect of
how both time pressure and task completion influence the time pressure alone is not strong enough to capture
occurrence of cognitive lockup. Therefore, this study people in their current task. We propose the following
extends the results found by Meij (2004). Furthermore, hypothesis:
the aim is to identify critical situations in cockpit
environments that allow for designing cockpit systems 1. Time pressure has no effect on cognitive lockup.
that help pilots avoid critical situations and decrease the That means, in case people deal with a task, and
probability for cognitive lockup. In the following another more urgent task is triggered, people
subsections we translate the research question into switch to the more urgent task just as often under
hypotheses. time pressure as when there is no time pressure.
Time pressure. Time pressure is the perception that time Task completion. Task completion literature (Garland
is scarce. According to Beevis (1999) people experience and Colon, 1993; Boehne and Paese, 2000; Humphrey
time pressure when the time required to execute tasks is S.E., Moon, H., Conlon, D.E., Hofmann D.A., 2004)
more than 70% of the total time available for the tasks. shows that people have the tendency to complete a task
Beevis (1999) suggested that people experience high time even if it is economically unwise to do so. Garland and
pressure when 85% of the available time is required to Colon (1993) and Boehne and Paese (2000) found that
execute the tasks. In this case performance is often this tendency is strongest when 90% of the task is
impaired in that some tasks are not (well) executed. Other completed compared to 10% or 50% completion of a
researchers (e.g. van der Kleij, 2009; De Dreu, 2003; task. Meij (2004) found an effect of task completion on
Durham et al., 2000; Karau and Kelly, 1992; Kelly and cognitive lockup. People tend to complete a task when
Loving, 2004) indicated the following consequences of they are almost finished (high task completion) even
time pressure. At the individual level, time pressure leads when a more urgent task is triggered. We expect that the
to (1) faster performance rates, because people stop results of Meij (2004) are replicated in this study.
considering multiple alternatives, (2) lower performance Therefore, we propose the following hypotheses:
quality, due to the engagement in superficial rather than
thorough and systematic processing of information, and 2. Task completion has an effect on cognitive
(3) more heuristic information processing, as a result of lockup.
refraining from critical probing of a given seemingly a. When task completion is high, the probability
adequate solution or judgment. At group level, increasing for cognitive lockup increases.
levels of time pressure narrows team members’ focus on That means, in case people deal with a task, and
a limited range of task-salient cues in both team another more urgent task is triggered, people
interaction patterns and team task performance. This tend to stick to the current task, when they have
narrow focus of attention that often manifests as a almost completed this task.
restricted information exchange is due to a filtering b. When task completion is low, the probability for
process (Kelly and Loving, 2004). Groups working under cognitive lockup decreases. That means, in case
time pressure attend to all of the information available people deal with a task, and another more urgent
but then selectively discuss only information that seems task is triggered, people tend to switch to the
especially relevant (Kelly and Loving, 2004). They also more urgent task when the first task is not nearly
found that under high time pressure group members see completed.
task completion as their main interaction objective, and
the group attempts to reach consensus and complete the
task as quickly as possible, but at the sacrifice of quality.
Groups under mild or no time pressure can, in contrast,
1
consider a wider set of task features, devote their In the research of Grootjen et al. (2006) time pressure was
resources to performing on the task as well as possible, high when the percentage of the available time for a task that
people are occupied with the task was high.
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
Interaction between time pressure and task Apparatus and material
completion. Meij (2004) suggested that when task The experiment included two laptop computers with
completion and time pressure are high the tendency for headphones. Java software was installed on the
cognitive lockup increases. When time pressure is high computers to run the experimental task and a training
but task completion is low, the tendency for cognitive session. Before the experiment, participants received a
lockup decreases. In fact, he investigated the interaction hardcopy manual printed on paper with A4 format.
effect between prior investments and task completion and During the experiment, participants could use a question-
attributed the effect of prior investments to the perception tree (see Figure 2) printed on paper with A4 format for
of time pressure. Thus, Meij never investigated the effect reference purposes.
of time pressure and task completion. Therefore, in this
study, we test whether high time pressure and high task Procedure
completion indeed increase the probability for cognitive
lockup and that high time pressure and low task The experiment was conducted at TNO in a computer
completion decrease this probability, as suggested by room, at the University of Utrecht in a laboratory, and in
Meij. We propose the following hypotheses. a private setting with the use of laptops. The experiment
took ca. 30 minutes per participant: 15 minutes for a
training (including test scenarios) and 15 minutes for the
3. There is an interaction effect between task experiment.
completion and time pressure on cognitive The participants received an information letter
lockup. upfront the training and an informed consent document
a. When time pressure is high and task completion after the training. The aim of the training was to
is high, the probability for cognitive lockup is familiarize the participants with the experimental task.
highest compared to all other conditions. That The training involved reading the training manual, which
means, in case people deal with a task, and was accompanied by a verbal instruction and executing
another more urgent task is triggered, people test scenarios on the computer. After the training the
tend to finish the first task before switching to participants were asked whether they felt comfortable
the more urgent when they feel time pressure with performing the task. If so, the experiment was
and have almost completed the first task. started. If not, questions could be asked and the test
b. When time pressure is high and task completion scenarios could be done again until the participant was
is low, the probability for cognitive lockup is comfortable with executing the task
lowest compared to all other conditions. That The experimental task was a computer
means, in case people deal with a task, and simulation in which participants had to fight fires on a
another more urgent task is triggered, people ship. The fire-fighting software was chosen because Meij
tend to switch to the urgent task before (2004) already demonstrated that with this fire-fighting
executing the first task when they feel time task cognitive lockup could be found.
pressure, but still need to complete many stages
to complete the first task.
Experimental task. In the experimental task participants
This study extends the study conducted by Meij (2004) as had to fight fires on a ship. Two types of fires existed:
we expect to provide further evidence for the explanation • normal fires, which were indicated by a red
that cognitive lockup is caused by a decision making triangle
bias, and that this bias could be triggered by time • urgent fires, which fires were indicated by a blue
pressure and task completion. triangle in a yellow background
Next to the fire type, fires had specific features. For
Method example, a fire could be an oil fire, a fire could be life
threatening, injured people could be involved, and/or
Participants smoke could trouble the sight of the firemen. Therefore,
The experiment counted 46 participants. The participants each fire required a specific action based on the fire’s
consisted of: specific features. To find out the fire specifics,
• TNO trainees/employees (15) participants could ask four predefined questions. These
• students of the University of Utrecht (20) questions appeared as buttons on the screen. To ask a
• (ex)members of the Hockey Club Rotterdam (6) question, participants had to press the question button.
• other (5) Figure 1 shows the screen that was visible to the
All participants were experienced computer users and participants once a fire was present. When a question was
most of them were highly educated. They were all asked, the system closed for four seconds to answer the
between the age of 18 and 35 years old. Psychology question with Y (Yes) or N (No) for a normal fire. In case
students received course credits for participation in the of an urgent fire the system closed for one second to
experiment. All participants could win 20 Euro when answer the question. This was because an urgent fire was
they had the highest score in the experiment. more dangerous for the ship and needed quick handling.
Please note that when the system was closed nothing
could be done. Based on the answers generated by the
system, participants could select the appropriate action to
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
extinguish the fire. Figure 2 shows the question-tree be left to extinguish the second fire. This would give the
which indicates the appropriate action. Seven predefined incentive to switch to the second fire. As a result the
actions could be chosen. The action buttons also appeared switch incentives in these situations would not be
on the bottom of the screen, once a fire was present (see comparable. This problem was solved by not showing the
Figure 1). An appropriate action extinguished the fire; a time available for the second fire.
wrong action shut down the system for seven seconds. If participants extinguished a fire in time they
Thereafter, a new action could be selected, if time could win points. However, if they did not extinguish the
allowed it. fire in time, points were deducted and a burn down was
the result (see Table 1). This was done to emphasize the
fact that an urgent fire was more urgent than a normal
fire, as more points could be won or lost by respectively
extinguishing or missing an urgent fire. If one fire burned
down, another fire could still be extinguished if time
allowed it.
In the test scenarios (see scenarios) the second
fire was always an urgent fire. The time was set in such a
way that if a participant finished the first fire before
switching to the urgent fire, the urgent fire would burn
down. This was also done to emphasize the fact that an
urgent fire was urgent. If it was not handled quickly it
burned down. This also meant that if participants suffered
from cognitive lockup (finishing the first fire instead of
extinguishing the urgent fire first), they would have had a
lower score than participants who did not suffer cognitive
lockup. To ensure the motivation of the participants a
reward of 20 Euro was promised to the participant with
Figure 1: Screen of the ship visible to participants once a the highest score. Participants only saw their score at the
fire was present. end of the experiment.
Are there any injuries?
Yes No
Table 1: Fire-fighting scores.
Is the fire an oil fire? Are there human lives at stake?
Action Points
Yes No Yes No
Extinguish normal fire 1
Is there any smoke output? Action: 2 Is the fire an oil fire? Is the fire an oil fire? Extinguish urgent fire 3
Yes No Yes No Yes No Burn down normal fire -1
Action: 1 Action: 3 Action: 3 Action: 4 Action: 5 Is there any smoke output?
Burn down urgent fire -3
Yes No
Action 1: Send a large injury team Experimental design
Action: 6 Action: 7
Action 2: Transport casualties
The main goal of this experiment was to investigate how
Action 3: Send a small injury team
Action 4: Extinguish with foam
time pressure and task completion influence the
Action 5: Cool cabin occurrence of cognitive lockup. In order to enhance the
Action 6: Remove smoke sensitiveness to find cognitive lockup, we operationalized
Action 7: Close doors
cognitive lockup in two ways. In the first definition
cognitive lockup was only found when participants did
Figure 2: Question-tree and relevant actions to extinguish
not switch to the urgent fire, when dealing with the first
fires. fire. In the second definition cognitive lockup was found
Participants knew how much time they had to when participants significantly delayed their switch to the
extinguish the first fire, as this was indicated by the timer urgent fire. Therefore, the second analysis was more
at the bottom of the screen. The time to stop a second fire sensitive to find cognitive lockup than the first analysis.
was not indicated. This was done to make the decision to
switch to the second fire similar for the different test 1) Cognitive lockup 1 was defined as completing the
scenarios (see scenarios). In case the time available first fire before extinguishing the second more urgent
would be shown for the second fire as well as, fire. Cognitive lockup 1 was measured as the mean
participants could depend their decision to switch on the percentage of scenarios in which cognitive lockup
time available for both fires. In the high task completion occur.
condition relatively little time would be left for the first 2) Cognitive lockup 2 was defined as delayed switching
fire and therefore relatively more time would be left to to the second more urgent task once presented, while
extinguish the second fire, which would give the executing a first task. Cognitive lockup 2 was
incentive to finish the first fire. In the low task measured as the action time to switch to the urgent
completion condition relatively much time would be left fire, once present (a significantly delayed action time
to extinguish the first fire, and relatively less time would indicates cognitive lockup).
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
fire first, but in that case the urgent fire would burn down
In order to investigate the influence of time pressure and as explained before.
task completion on cognitive lockup, time pressure and In the low time pressure condition the available
task completion were manipulated within-subjects. time to extinguish the first fire was 55 seconds for all
fires. In this condition time pressure was ≤ 40%, as 40%
Task completion. Task completion was defined as the or less of the available time was required for the task.
percentage of the total number of stages of a task that The available time of 55 seconds was chosen because
have been completed. People have the tendency to stick perceived time pressure of the first fire could be
to their current task when 90% or more of the total stages influenced by the appearance of the second more urgent
of a task have been completed (Boehne and Pease, 2000; fire. To make sure that participants would perceive little
Garland and Colon, 1993). We investigated whether time pressure in the low time pressure condition, 55
people refrain from switching to an urgent second task, seconds allowed the participants to start with the first
when they have almost completed a first task. Therefore, fire, and when the urgent fire appeared to switch to the
task completion was manipulated by the onset of the urgent fire and once the urgent fire was extinguished, to
urgent fire. The onset depended on the number of switch to the first fire again and extinguish the first fire.
questions that had been asked in order to extinguish the Thus, in the low time pressure scenarios the maximum
first fire. In the high task completion condition the urgent score of four points could be obtained. Table 2
fire appeared after three questions had been asked. In this summarizes the test conditions in terms of task
condition task completion of the first task was 75%, as completion and time pressure.
75% of the total stages of the task had been completed
(three questions answered out of four). This percentage Table 2: Test conditions.
was chosen because this was the pre-final stage for
extinguishing the first fire, and closest to 90% task Test Time pressure Task completion
completion as mentioned by Boehne and Pease (2000) condition (%) (%)
and Garland and Colon (1993). In the low task Low-Low ≤ 40 25
completion condition the urgent fire appeared after one Low- High ≤ 40 75
question had been asked. In this case task completion was High-Low ≥ 88 25
25%, as 25% of the total stages of the first task had been High-High ≥ 88 75
completed (one question answered out of four).
Scenarios. The experiment consisted of 25 scenarios.
Time pressure. Time pressure was defined as the The scenarios included 8 test scenarios (2 times all test
percentage of the available time to execute a task that is conditions) and 17 irrelevant scenarios. The irrelevant
required to execute the task. People experience time scenarios were designed in order to accomplish
pressure when 70% or more of the available time is uncertainty, so the participants would not understand the
required for the task (Beevis, 1999). People experience test scenarios. The test scenarios can be described as
high time pressure when 85% of the available time is follows:
required for the task (Beevis, 1999). The average time to 1. In the scenario where time pressure was low and task
fight a fire depended on the number of questions that had completion was low, participants had 55 seconds to
to be asked to extinguish a fire. Based on the pilot results fight the first fire. The urgent fire appeared when
it appeared that for a normal fire the time required to they had asked one question of the first fire. The
extinguish a fire based on four questions was 22,1 urgent fire needed to be extinguished in 17 seconds.
seconds; based on three questions this was 18,6 seconds If participants decided to extinguish the first fire
and based on two questions this was 14,3 seconds. We first, the available time allowed participants to start
investigated whether time pressure on a first task would with the urgent fire, after they had extinguished the
refrain people from switching to a second more urgent first fire, but they would never be able to extinguish
task. Therefore, time pressure was manipulated. This was it. In this way the participants would not be
achieved by increasing or decreasing the time available demotivated, which would be the case when the
for fighting the first fire. urgent fire had already burned down, while still
In the high time pressure condition the available fighting the first fire.
time to extinguish the first fire was 25 seconds for fires 2. In the scenario where time pressure was low and task
that needed four questions and 20 seconds for fires that completion was high, participants had 55 seconds to
needed three questions. Fires that needed two questions fight the first fire. The urgent fire appeared when
were not present in the test scenarios (see scenarios). In they had asked three questions of the first fire. The
this way time pressure was ≥ 88%, as 88% or more of the urgent fire needed to be extinguished in 13 seconds.
available time was required for the task. As a result, in In this way it was impossible to extinguish the first
the high time pressure and high task completion scenario fire first, and afterwards extinguish the urgent fire.
the available time to extinguish the first fire was almost 3. In the scenario where time pressure was high and
over when the urgent fire appeared. Therefore, task completion was low, participants had 20
participants had to choose for the urgent fire at the cost of seconds to fight the first fire. This was because the
a burn down of the first fire in this condition. Thus, they first fire could be extinguished after three questions.
could never obtain the total payoff of four points in this The urgent fire appeared when they had asked one
scenario. They could also choose to extinguish the first
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
question of the first fire. Like scenario 1, the urgent before the participants switched to the more urgent
fire needed to be extinguished in 17 seconds. second fire.
4. In the scenario where time pressure was high and 70
task completion was high, participants had 25 60
seconds to fight the first fire. This was because the
50
first fire could only be extinguished after four
CL 1 (%)
40
questions. The urgent fire appeared when they had
30
asked three questions of the first fire. Like scenario 2
the urgent fire needed to be extinguished in 13 20 Time Pressure
seconds. 10 Low
0 High
The scenarios (test and irrelevant scenarios) were -10
Low High
presented in random order to avoid order effects. Only Task Completion
the test scenarios were analyzed.
Figure 3: The mean percentage of scenarios in which
Statistical design CL1 was found.
The experimental design was a repeated measures design,
as each test condition consisted of two scenarios. Thus, The main effect of task completion on CL1 was
the participants received all test conditions twice. significant, F(1,44) = 36.857, p < .001. This means that
Therefore, we used a 2x2x2 repeated measures ANOVA the percentage of scenarios in which CL1 was found was
with attempts, time pressure and task completion as significantly higher in the high condition (Mean = 43%)
factors to analyze the data. compared to the low condition (Mean = 11%). In other
Before the experiment was executed, we words when participants had almost extinguished the first
conducted a power analysis in order to examine the fire (one question to go to find out the correct action)
number of participants needed for the experimental more people finished the first fire before switching to the
design. The power analysis for a factorial ANOVA urgent fire than when the participants still had three
suggested a sample size (N) of 45 to achieve a power of questions to go to find out the correct action. There was
0.80 for detecting a medium effect size (0.26) and alpha no effect of time pressure or an interaction effect found
set at 0.05. Hence, this design required a sample size of between task completion and time pressure on CL1.
45 participants to be able to conduct further statistical Next to these results, a significant main effect was found
analysis. Based on this result, 46 participants were for the factor attempts (not shown in Figure 3). The
recruited. participants received all test conditions twice. The results
show that the mean percentage of scenarios in which CL1
Results was found was significantly higher in the first attempt
(Mean = 34%) compared to the second attempt (Mean =
Sample data 21%) F(1,44) = 10.203 p < .003. This indicates a learning
effect.
In the experiment 46 cases with two repeated measures Figure 4 shows the results for attempt 1 and 2
were recorded. Three records were removed as one separately. For both attempt 1 and 2, a significant main
participant did not follow the experiment instruction effect for task completion was found F(1,44 ) = 26.362, p
correctly and pressed action buttons without asking < .001 and F(1,44) = 24.750, p < .001, respectively. No
questions. Therefore, this data could not be analyzed as effect was found for time pressure. In addition, no
the urgent fire was not triggered. Table 3 shows the interaction effect between time pressure and task
number of valid records per test condition. completion was found.
ATTEMPT: 1 ATTEMPT: 2
Table 3: Number of valid records per test condition.
80
70
Test condition Number of records
Time Task Attempt 1 Attempt 2 60
Pressure Completion 50
CL 1 (%)
Low Low 46 46 40
Low High 45 45
30
High Low 46 46
20
High High 45 46
10 Time Pressure
Low
Cognitive lockup 1 0
High
Figure 3 shows the mean percentage of scenarios in -10
Low High Low High
which cognitive lockup 1 (CL1) was found, taking time Task Completion Task Completion
pressure and task completion into account. In other
words, the Figure shows the mean percentage of Figure 4: The mean percentage of scenarios in which
scenarios in which the normal fire was extinguished CL1 was found for attempt 1 and 2.
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
Cognitive lockup 2
ATTEMPT: 1 ATTEMPT: 2
Figure 5 shows the mean reaction times of participants to 9
switch to the second more urgent fire, while fighting the
8
first fire. Cognitive lockup 2 (CL2) was found when the
reaction times were significantly longer in a specific 7
CL 2 (seconds)
condition. 6
8,0 5
7,5 4
7,0
6,5
CL 2 (seconds)
3 Time Pressure
6,0
Low
5,5 2
5,0 High
4,5 1
Low High Low High
4,0 Task Completion Task Completion
Time Pressure
3,5
3,0 Low Figure 6: Time needed in seconds to switch to the urgent
2,5 High
fire for attempt 1 and 2.
2,0
Low High
Task Completion
General Discussions
Figure 5: Time needed in seconds to switch to the urgent
fire. The main goal of this experiment was to investigate how
both time pressure and task completion influence the
The main effect of task completion on CL2 was occurrence of cognitive lockup. Firstly, we hypothesized
significant, F(1,44) = 15.182, p < .001. This means that that time pressure alone would not have an effect on
the participants needed more time to switch to the urgent cognitive lockup (hypothesis 1). The results of the
fire in the high condition (Mean = 5,9 seconds) compared experiment support this hypothesis. In case people deal
to the low condition (Mean = 4,1 seconds). In other with a task, and another more urgent task is triggered,
words, when participants had already asked three people switch to the more urgent task just as often and
questions of the first fire, it took significantly longer to just as fast under time pressure as when there is no time
switch to the urgent fire compared to the situation where pressure. This result implies that although time pressure
they had only asked one question. The average time to can trigger heuristic information processing and thereby
‘switch’ to the first fire, once it was present, was 1,1 influence decision making (e.g. van der Kleij, 2009; De
second. There was no effect of time pressure or an Dreu, 2003; Durham et al., 2000; Karau and Kelly, 1992;
interaction effect found between task completion and Kelly and Loving, 2004), people are able to assess the
time pressure on CL2. Next to these results, a significant priority of different tasks while dealing with a task, and
main effect was found for the factor attempt (not shown switch to the most important task if necessary. They are
in Figure 5). The participants received all test conditions not captured in their current task when facing time
twice. The results show that it took longer to switch to pressure.
the urgent fire in the first attempt (Mean = 5,8 seconds) We should mention that in the high time
compared to the second attempt (Mean = 4,1 seconds; pressure and high task completion condition there was an
F(1,44) = 15,444 p < .001). This indicates a learning incentive to extinguish the normal fire first, before
effect. switching to the urgent fire. As a result, this incentive
Figure 6 shows the results for attempt 1 and stimulated the chance to find cognitive lockup. The
attempt 2 separately. For both attempt 1 and 2, a incentive existed because a choice had to be made
significant main effect for task completion was found between the normal fire and the urgent fire. While
F(1,44) = 5.922, p < .019 and F(1,44 )= 14.404, p < .001 dealing with the normal fire, participants could see that if
respectively. No effect was found for time pressure. In they switched to the urgent fire, they would miss the
addition, no interaction effect between time pressure and normal fire. However, if they extinguished the normal
task completion was found. fire, there was only a chance that they would miss the
urgent fire. The participants did not know that the
maximum number of points could never be obtained, as
they would indeed miss the urgent fire, when they
extinguished the normal fire first. Participants with a risk
avoiding strategy would switch to the urgent fire as this
fire could be missed if they did not switch immediately
(two points versus minus two points). However,
participants that were very confident with extinguishing
the fires and who had a risky result maximizing strategy
could try to extinguish both fires instead of one (four
points versus two points). They would extinguish the
normal fire first. In this way, there was an incentive to
finish the normal fire first in the high task completion and
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
high time pressure condition. While this incentive was reported by Boehne and Pease (2000) and Garland and
present, nevertheless participants decided to switch to the Colon (1993). In their experiments they found the
urgent fire in the high time pressure and high task tendency to complete a task when the task has already
completion condition as often as in the low time pressure been completed for 90%. The present study shows that
and high task completion condition. This underscores our this tendency is already present when a task has been
finding that time pressure has no influence on the completed for 75%. In our experimental setup this was
occurrence of cognitive lockup. achieved when three task stages had been completed out
Furthermore, we should notice that we used a of a maximum number of four stages. It could be argued
static time deadline to manipulate time pressure. Other that participants perceived a higher task completion
ways exist to induce time pressure. For example, a more percentage as only one stage was still required to
dynamic task can be used in which deadlines evolve with complete the task.
different speed. This type of dynamic time pressure might These results imply that the perception that a
have different effects on performance (Kerstholt and task is almost competed could lead to critical situations
Willems, 1993). As a consequence, the results of this when another more urgent task is triggered. This urgent
study only apply to settings in which time pressure is task might be ignored as a result of cognitive lockup. In
induced by a static deadline. Further research is needed to order to avoid cognitive lockup we believe that the
analyze the effect on behavior when time pressure is tendency to complete a task when it is almost completed
dynamic. should be broken. For instance, this might be done by
Secondly, we hypothesized that task completion altering the perception that a task is almost completed or
would have an effect on cognitive lockup (hypothesis 2). by unlearning this tendency. Further research is needed to
The results of the experiment support this hypothesis. investigate how to break the tendency to complete a task
The results show that there is a main effect of task when it has almost been completed and a more urgent
completion on cognitive lockup (CL1 and CL2). People task is triggered.
that have almost completed a task tend to finish this task Finally, according to the results of Meij (2004)
even when a more urgent task is triggered. In other we hypothesized that there would be an interaction effect
words, when task completion is high the probability for between time pressure and task completion (hypothesis
cognitive lockup increases (hypotheses 2a). People that 3). The results do not support this hypothesis as the
still need to complete many stages before a task is interaction effect between time pressure and task
completed tend to switch to the more urgent task, when completion on cognitive lockup (CL1 and CL2) was not
triggered. Thus, when task completion is low the significant. The result implies that time pressure does not
probability for cognitive lockup decreases (hypotheses enhance the task completion effect, as expected. Thus,
2b). These results were found despite a learning effect. when task completion is high the probability for
We found that cognitive lockup was less present during cognitive lockup is not increased when people face time
the second attempt of a test scenario compared to the first pressure. The present study shows that the interaction
attempt. We believe that this was due to a learning effect. effect found by Meij (2004) between prior investments
People learned from the feedback they received in the and task completion on cognitive lockup cannot be
first attempt of a scenario, and if needed they changed explained by the perception of time pressure when prior
their strategy in the second attempt. However, the task investments are high, as he suggested. An alternative
completion effect remained significant in the second explanation cannot be given as prior investments were
attempt. Thus, although participants lost points when they not investigated in this experiment. Further research
completed the first fire and as a result missed the urgent should be done to find an explanation for the effect of
fire in the first attempt of the high task completion prior investments on cognitive lockup and why this factor
scenario, they did not change their strategy when the interacts with task completion.
scenario was executed again. The results of this study provide further support
It could be argued that the participants might not for the explanation that cognitive lockup up is the result
have perceived the urge of the urgent fires and as a result of a decision making bias and that this bias could be
stayed with the normal fires. Although the urgent fires triggered by the perception that a task is almost
had a very different icon, behaved differently (system completed. This has important implications for the
closure of one second instead of four after a button had designs of cockpits, as it indicates that decision support
been pressed) and generated more (less) points when tools seem more important in reducing the probability for
extinguished (burned down) than normal fires, the cognitive lockup than, for example, tools that reduce
categorization might not have been meaningful enough cognitive workload. The decision support tool should
for the participants. However, participants showed in the assist pilots to focus on the most urgent task. However, a
high time pressure and high task completion condition, in critical situation exists when the pilot has almost
which they had to choose between the urgent and normal completed a task and a more urgent task is triggered. The
fire, that they switched to the urgent fire as often as in the decision support tool might be ignored, as a result of
low time pressure and high task completion condition. cognitive lockup. To avoid critical situations it is
Such behavior would not have been expected when important that this decision support tool also helps pilots
categorization and consequences were not clear. to break the tendency to complete a task when it is almost
This study replicates the results of Meij (2004) finished and another more urgent task is triggered. In this
as he also found an effect of task completion on cognitive way pilots can act appropriately and deal with the most
lockup. Furthermore, this finding extends the results urgent task.
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CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011
Training Acknowledgments
Although the experimental design was not specifically The work described in this paper is funded by the
built to investigate an effect of training, a significant European Commission in the 7th Framework Programme,
learning effect was found. Participants showed less Transportation under the number FP7 – 211988.
cognitive lockup (CL1 and CL2) the second time they
executed the test scenarios, compared to the first time. As References
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