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amount of work to be completed in experimental research studies. A systematic review by D. Kelly and Sugimoto (2013) indicated that researchers reported the time allowed for task completion in 39% of the reviewed IIR studies while 42% did not mention the presence or absence of time constraints. In the cases where researchers did specify the time limits, the average time limit was 17 minutes (SD=13) with 15 as the median and mode. In some cases, researchers indicated the amount of time they allowed participants to complete tasks while others noted that there were time limits but did not specify the amount of time allowed. Kelly and Sugimoto also noted cases where researchers instructed participants to work quickly or provided additional financial incentives to study participants who completed their tasks quickly. These methods have been used to induce time pressure in experimental decision-making studies. The task instructions containing the criteria for ending a task also vary: search until all relevant documents are found, search untilndocuments are found, search until the time limit is reached, or even to search until satisfied with what you have found.

Inducing time pressure by manipulating time or time perception. Most frequently, time pressure is induced by manipulating the time allowed to complete a task (Crescenzi et al., 2016; Gilliland & Schmitt, 1993; Ordóñez & Benson, 1997) or a series of tasks (Rieskamp & Hoffrage, 2008) alone or in conjunction with other methods (e.g., warning of approaching end of time). Time manipulation might be subject to one or more time constraints, such as a deadline for when a task must be completed or time limit indicating the amount of time a person can take to complete a task or subtask. When a time limit is used to induce time pressure, the specific time allowed given to complete tasks or activities is often based upon the mean completion time in a prior or pilot study in which no time limits were imposed (e.g., Gilliland & Schmitt, 1993; Hertzum & Holmegaard, 2013b; Ordóñez & Benson, 1997). These methods include setting the time allowed under time pressure equal to the mean minus standard deviation (e.g., Huber & Kunz, 2007; Maule, Hockey, & Bdzola, 2000; Ordóñez & Benson, 1997), or half of the mean from pilot testing or previous studies (e.g., Crescenzi et al., 2016; Gilliland & Schmitt, 1993; Weenig & Maarleveld, 2002). For example, to induce

time pressure, Crescenzi et al. (2015) set a time limit corresponding to 50% of the mean task completion time for tasks used in a different study using the same system without a task time constraint. In other cases, researchers have manipulated time pressure without manipulating the amount of time allowed by instructing participants to work as fast as possible (e.g., Fehrenbacher & Smith, 2014).

Other researchers have used visual representations of time passing to induce time pressure or provide awareness of time. Luo et al. (2016) included a timing bar on the search interface above the query box; the timing bar changed from green to red and flashed more frequently as a participant spent more time on task. Maule et al. (2000) displayed a timing bar which shrunk as time elapsed and disappeared when time ran out. Weenig and Maarleveld (2002) used two different time cues for the low and high time pressure conditions. A countdown timer was displayed in the high time limit condition (with a time limit) and a clock showing the time was present for the low time pressure condition which had no time limits.

Time pressure has also been induced by manipulating the perception of time adequacy through in- structions telling participants the time is inadequate to complete the tasks (Alison, Doran, Long, Power, & Humphrey, 2013; J. R. Kelly & Loving, 2004). Other methods for drawing attention to time to induce time pressure have included an audible noise in the room (e.g., a metronome in Inbar, Botti, & Hanko, 2011), having a member of the research team pace the room (e.g., Stone & Kadous, 1997), or by notifying participants of elapsed time (e.g., Luo et al., 2016; Wright, 1974) or time remaining until the time limit is reached (e.g., Maule et al., 2000). For example, to induce a feeling of rushing in half of participants, Inbar et al. (2011) used two different rates of audible metronome ticks (80 vs. 40 ticks/minute). Wright (1974) used multiple methods: indicating time passing by writing the elapsed time on the board every 10 seconds, instructing participants to work as rapidly as possible, and asking participants to note on their paper how much time they spent on each task.

Inducing time pressure by manipulating work or work perceptions. Researchers have also induced time pressure by varying the work to be done without varying the time allowed. This has been accomplished by giving participants more tasks to complete in a time-pressured condition (e.g., Baumann, 1998) or by giving tasks that were more cognitively complex (Crescenzi et al., 2017). For example, imposed search tasks of varying levels of cognitive complexity were assigned in Crescenzi et al. (2017) without varying the amount of time allowed. They found significantly higher levels of perceived time pressure in tasks that were more cognitively complex. Time pressure has also been induced by interrupting a primary task with additional work in the form of a secondary task. Increased time pressure due to interruptions has been found

in experimental settings (Hertzum & Holmegaard, 2013b; Mark, Gudith, & Klocke, 2008) and in experience sampling studies (Baethge & Rigotti, 2013).

Time pressure has also been induced by varying both work and time. These methods include varying the rate of information presentation (e.g., Matthews & Campbell, 1998), or imposing additional work if participants do not finish their task on time (e.g., Ordóñez & Benson, 1997). In other cases, researchers have determined the amount of participants’ financial incentives based upon the amount of work completed in a given amount of time (e.g., Marsden, Pakath, & Wibowo, 2006) or the time taken to complete a given amount of work (e.g, J. W. Payne, Bettman, & Luce, 1996; Rieskamp & Hoffrage, 2008).

Self-imposed time pressure. In addition to the time pressure induced by researcher-imposed time constraints, participants may experience time pressure from self-imposed time constraints. As MacGregor (1993) notes, all decisions have an externally-imposed or self-imposed time frame:

all decisions and choices occur under time pressure, within a time frame that has a deadline, either self-imposed by an individual, or established by the external context in which the behavior occurs. The time frame is initiated by internal events (e.g., a perceived need to make a decision), external events (e.g., task demands of an occupation), or by both. (p. 74)

The interview subjects in Mansourian and Ford (2007) noted two types of time constraints for their information searches: time constraints imposed by external factors over which the searcher does not have control, and self-generated time constraints where a searcher prefers to limit their time spent for the search.

Removing or preventing time pressure. In some cases, researchers have recognized the possibility of self-induced time pressure and attempted to remove self-induced time pressure or induce low levels of time pressure through instructions to participants (Eysenbach & Köhler, 2002) or experimental manipulations (e.g., J. Chen & Proctor, 2017; Wright, 1974). In some cases, researchers have noted making experimental design decisions to attempt to reduce variability in perceived time pressure or to avoid inducing time pressure. For example, Jarvenpaa, Dickson, and Desanctis (1985) manipulated both task complexity and the time available to complete tasks in order to induce similar levels of time pressure across tasks to avoid confounding their results. Others have explained their experimental design decision to not limit time on task to intentionally avoid inducing time pressure prevent its potential impact to results (e.g., Borlund & Ingwersen, 1997). Several studies of information-seeking or information search have described the time pressure perceived by study participants as a factor which may have inadvertently impacted their results and/or be an alternative explanation for results found (e.g., González-Ibáñez, Haseki, & Shah, 2013; Kules & Shneiderman, 2008).

There are other issues with time pressure in experimental studies, including individual variability in sensitivity to time pressure (e.g., Crescenzi et al., 2013; Francis-Smythe & Robertson, 1999; Chang Liu et al., 2019). In addition, some researchers have found carryover effects of time limits in studies with repeated- measures (Ordóñez & Benson, 1997; J. W. Payne et al., 1988; Rieskamp & Hoffrage, 2008) suggesting that once an individual changes their strategy in response to induced time pressure, it may not be possible to undo this change. In pilot testing, Ordóñez and Benson (1997) found carryover effects of a within-subjects time pressure manipulation:

Pilot testing indicated that simply mentioning that there would be a time constraint in later trials caused subjects to significantly reduce their response times in the unconstrained trials. Time constraints were therefore not mentioned in these initial trials. (p. 125-6)

J. W. Payne et al. (1988) also found carryover effects across multiple days of a study.

Manipulation checks.Some studies verified the effectiveness of their experimental conditions by asking one to three questions about perceived time pressure as a manipulation check (e.g., Crescenzi et al., 2015; Maule et al., 2000; Ordóñez & Benson, 1997), while others have assumed that their manipulation methods lead to experienced time pressure (e.g., Chang Liu et al., 2019). Experimental manipulations designed to induce time pressure are often based on pilot testing or a review of the literature, but it is difficult to know if the experimental manipulation was successful if manipulation checks are not performed. This is especially important if the researchers did not find any significant differences in behaviors between time conditions (e.g., Farri et al., 2013).