Table of Reactivity Tasks

John D. and Catherine T. MacArthur
Research Network on Socioeconomic Status and Health

Laboratory Tasks for Cardiovascular Reactivity Research

Task	Description	Autonomic Pattern	Comments
Reaction Time	Respond to a tone as quickly as possible. Has been used with and without monetary incentives. Other variations include simple RT in which subject responds to a single tone, and choice RT in which a response is made to one tone but not a different tone. RT can be either signalled or unsignalled, but psychophysiological studies using RT as a stressor have usually used unsignalled (subject doesn’t know when tone will occur). Length of time usually ranges from 3 to 5 minutes, although occasionally up to 10 minutes. Occasionally used with harassment.	Beta-adrenergic response is most consistent. PNS withdrawal is common.	Modal RT response is moderate HR and SBP increase, small or no increase in DBP, substantial change in contractility indices (e.g., PEP). Pattern of response in strong reactors is very similar to mild exercise. Pattern is consistent across a variety of incentive levels, although absolute magnitude of response may be larger with monetary incentives or shock avoidance. Requires computer or other electronics if RT performance data is desired.
Public Speaking	Subjects given a short period to compose a speech that they must then give in front of an audience or video camera. Subject matter of the speech is usually of a stressful nature, such as having to convince a judge of being innocent of shoplifting. Many studies have used 2 min of preparation time and 3 to 5 minutes for the speech. Has been used with harassment as an added incentive.	Beta-adrenergic and mixed beta and alpha is most typical. Large PNS withdrawal.	Large increases in HR and blood pressure are typical, as well as increases in contractility indices. DBP response is generally larger than RT, implying more vasoconstriction than RT and a less "pure" beta response. One drawback is the lack of control of the amount of talking by the subjects and the ability to compose a speech. An advantage is that it requires little if any equipment.
Mirror Star Tracing	Subject must trace the outline of a star using a metal stylus or pencil while not being able to see the star directly but a mirror image of it. Up and down visual cues are therefore reversed. Task usually lasts from 3-10 minutes. Requires an apparatus manufactured by Stoelting Co. Can be interfaced to a computer to keep up with % time on the star, and can also be scored for number of star segments successfully traced.	Alpha-adrenergic response is most common. Some PNS withdrawal.	Is described as a frustrating task by many. Produces small to moderate increases in HR, with larger increases in DBP and peripheral resistance. Is too difficult for many children under 10 years, and some adults find it very difficult and "give up."
Mental Arithmetic	Two major variations: 1) countdown task in which subject must subtract some number (e.g., 17) sequentially from a large number as fast as possible, and 2) working math problems mentally that are generated by a computer which also provides feedback on performance. Harassment has been frequently used to make the task more stressful.	Mixed alpha and beta-adrenergic, although most subjects respond with a more beta pattern. PNS withdrawal.	Modal MA response is significant HR and blood pressure response. Contractility is generally not as strong as RT, but HR response may be greater than RT, resulting in approximately equal increases in cardiac output. The use of a computer-generated MA minimizes extraneous motor movement and lack of control over verbalization in the countdown task. Countdown requires no equipment, whereas computer MA does.
Stroop Color-Word Inter-ference Task	Color words written in various colors are presented usually via slides or computer; subject must say or select the ink color rather than the name of the color spelled out by the word. "Stress" is created by the interference between the discrepant ink color and color name.	Mixed alpha and beta pattern, although alpha is perhaps more common.	Moderate HR and blood pressure response. Many subjects quickly adapt to this task, so harassment or other incentives may be necessary to keep up subject’s interest if the task runs longer than about 3 minutes.
Cold Pressor (Hand or foot)	Immersion of hand up to wrist or foot up to ankle in ice water (~4° C). Some investigators use a stirring device to keep the water moving to increase the cold. As the cold can make subjects breathe erratically and hyperventilate, some researchers have subjects quietly count to themselves during cold exposure to facilitate a more normal breathing pattern. Most investigators use 1-2 minutes of immersion.	Alpha-adrenergic is the common response, although beta pattern is less commonly seen. Usually a PNS withdrawal, but is dependent on breathing pattern.	Modal response is large increase in HR and both SBP and DBP. Large increase in peripheral resistance with decreased stroke volume. Cardiac output is usually unchanged from baseline or reduced. Beta-like pattern is sometimes seen when subjects hyperventilate. Very painful to many people. Blood pressure response may be linked to degree of pain experienced.
Cold Forehead	Often referred to as the forehead cold pressor as an icebag is applied to the forehead. Counting is also used to encourage normal breathing. Can be used successfully with children. 1-2 minutes of exposure is common.	Alpha-adrenergic is the common response, but an increase in PNS activity is usually present.	Large BP and peripheral resistance response is common, although the HR response is usually small or levels may even go below baseline due to the "dive reflex." The cold pain is difficult for some to tolerate, and it may produce a migraine headache in susceptible individuals. Although this task is often thought to be just a variation on foot or hand immersion, the HR response is quite different.
Isometric Handgrip Exercise	Subject squeezes and holds a designated amount of tension on a handgrip dynamometer. Most commonly the task involves holding 30% of maximum grip strength for a period of time, usually between 3 and 5 minutes.	Alpha-adrenergic is most common, along with PNS withdrawal.	Similar to cold pressor with large increases in blood pressure and moderate HR increases. Large increases in peripheral resistance. Exercising arm may become ischemic with muscle contraction impeding blood flow in and out of forearm muscle. Disadvantages include much uncontrolled muscle contraction other than working muscle, and large gender differences in the amount of maximal grip strength.
Distress recall tasks	The main theme is that subjects are requested to describe and perhaps "relive" stressful events in their lives. Variations include describing the most frustrating person or event in one’s life (e.g., Lamensdorf & Linden, 1992), and the Social Competency Interview of Ewart and colleagues which asks subjects to describe stressful events in their lives. Task usually runs from 5 to 10 minutes.	Mixed beta- and alpha-adrenergic. PNS withdrawal.	The significant increases in HR and blood pressure are similar to those seen with public speaking. Wide range of responses seen with this task. As with public speaking, one drawback is the uncontrolled nature of what the person chooses to talk about and the amount of talking.
Video Games	Various commercially available video games such as Atari Breakout, Apple Gunslinger, and arcade games have been used. Most involve tracking a target, responding quickly to a stimulus, and good eye-hand coordination. Usually run from 3-10 minutes.	Mixed alpha- and beta-adrenergic with moderate PNS withdrawal.	Usually produce moderate increases in HR and blood pressure. Responses tend to be variable from person to person, maybe due to motivation level and familiarity with playing video games. The latter is a drawback to their use, along with a lot of uncontrolled muscle movement.
Type A Structured Interview	This interview (SI) is used to assess the Type A behavior pattern, but has also been used as a laboratory stressor. The interview probes for potential for hostility, impatience, speech stylistics, etc.	Mixed pattern with alpha-adrenergic most dominant.	The magnitude of HR and blood pressure response to the SI is generally less than that to the public speaking task and the other distress interviews. As questions deal with a number of different areas, the use of this interview as a lab stressor may produce more inconsistent results.
Distressing Films	A variety of distressing films have been utilized, having in common an elicited repulsion in most people. Examples include autopsy films, driver education films of automobile accidents, industrial accident films (e.g., fingers cut off by band saw, etc.), and childbirth films.	Primary response seems to be an activation of the PNS system.	The modal response is an increase in heart rate which is mediated by an increase in parasympathetic nervous system activity. Some individuals do have a sympathetic response to the films, but PNS is more common. Extreme PNS activation can lead to fainting as can be seen with these films.
Graded Isotonic Bicycle Exercise	Subjects pedal a bicycle ergometer at a number of steadily increasing submaximal workloads (e.g., 25, 50 and 75 watts). Each workload should be at least 5 minutes duration in order for subject to obtain a steady state.	Beta-adrenergic activation with large PNS withdrawal (Exercise response)	Large increases in HR, SBP, and myocardial contractility indices, with little to no change in DBP and reduction in peripheral resistance. This task usually serves as a comparison for other laboratory stressors and/or to establish relationships of HR or cardiac output change with oxygen uptake changes.
Anagrams	Task involves finding meaningful words from lists of scrambled letters. Difficulty can be easily manipulated from easy to unsolvable. Has been used in a few studies, although not widely used. Task usually ranges from about 3-10 minutes.	Mixed beta- and alpha-adrenergic pattern. No PNS data available.	Moderate HR and blood pressure response. Has the advantage of minimal muscle movement, but there is large variability in the ability of individuals to solve anagrams.
Raven’s Progress-ive Matrices	Essentially a series of visual puzzles in which the subject must choose the next logical matrix pattern in a series. Successful performance involves good visual-spatial abilities. Has not been used in a large number of studies. Task range is again about 3-10 minutes.	From the limited data available, appears to be a mixed alpha and beta pattern similar to mental arithmetic, but somewhat less in magnitude.	Moderate increases in HR and blood pressure. As with anagrams, one advantage is that the difficulty level can be easily varied. However, this is a task that many individuals find quite challenging, and some will give up if the matrices are too difficult.

Compiled by: Michael T. Allen, Ph.D.
Division of Education and Psychology
University of Southern Mississippi - Gulf Coast
Long Beach, MS 39560
(228) 214-3253
E-mail: Michael.Allen@usm.edu

Descriptions of Table Terms and Notes on Interpretation

1. Alpha-adrenergic activation: this term is used to describe a pattern of sympathetic nervous system activation that primarily produces constriction of arterioles with some increase in heart rate. Increases in diastolic blood pressure and total peripheral resistance are characteristic of this type of activation, along with moderate heart rate increases. The term comes from a particular type of adrenergic receptor that is present in many tissues and vessels and causes vasoconstriction. Similar to the response seen with exogenous norepinephrine injection.

2. Beta-adrenergic activation: this term is used to describe a pattern of sympathetic nervous system activaiton that produces marked increases in contractility of the heart, an increase in heart rate, and vasodilation in certain tissue beds, especially skeletal muscle. Resultant cardiovascular pattern is a large increase in heart rate, large decreases in variables sensitive to contractility such as pre-ejection period, large increases in systolic blood pressure due increased contractility, but little increase or even a decrease in diastolic blood pressure due to the drop in vascular resistance due to vasodilation in skeletal muscles. Similar to the response seen with exogenous epinephrine injection.

3. Parasympathetic nervous system (PNS) changes: PNS influences on most cardiovascular variables are predominant at rest with little or no sympathetic influence. With the addition of a stressor, the PNS activity to the cardiovascular system usually lessens (PNS withdrawal), the amount being dependent on the type of task and degree of arousal. PNS activity mainly affects heart rate with only small influences on contractility. PNS withdrawal results in heart rate increases, whereas increased PNS activation slows heart rate. The cold forehead stimulus in which the cold applied to the face is unlike most tasks because it stimulates the trigeminal nerve which in turn stimulates the increase in PNS activity. Thus it tends to slow heart rate down. This reflex, called the dive reflex, is quite powerful in aquatic mammals, but is present vestigially in humans. PNS activation can also be observed when subjects view repugnant films as described in the table.

4. Some previous attempts to characterize tasks by their autonomic pattern have been 1) active coping versus passive coping, and 2) sensory intake versus sensory rejection. Active coping tasks were described as those requiring "effortful striving, " meaning that subjects were faced with a challenge that they felt could be accomplished if sufficient effort was expended. These tasks were thought to be likely to elicit a beta-adrenergic pattern of response. Passive coping tasks were those in which the subject had to passively accept the administration of the task with no ability to control it (e.g., the cold pressor task), or where the task was so difficult that effortful striving would not be of any value. These tasks were suggested as eliciting a more "alpha" pattern and/or PNS activation. This active-passive distinction is not perfectly predictive of task response, but it has been useful in designing tasks.

Sensory intake tasks are those that require the subject to attend to the environment and focus in on the task in order to do well (e.g., a reaction time task); these have been postulated as resulting in an acute heart rate decrease in anticipation of the stimulus. Sensory rejection tasks are those requiring mental ideation (such as mental arithmetic) in which the environment is blocked out in order to maximize the internal ideation without interference. These tasks have been postulated as causing an increase in heart rate. This distinction has been useful for describing patterns of heart rate response to individual stimuli, but not necessarily to overall heart rate means across the entire task.

5. It should be kept in mind that the descriptions of autonomic and cardiovascular patterns are those taken from group means of individuals, so the issue of how representative the patterns are for individuals can be raised. There are large individual differences in the responses to the tasks, and the patterns represent the modal response. To say, for example, that reaction time tasks are primarily beta-adrenergic reflects that a beta pattern is the most common pattern seen. It may also mean that a task is described as having a "mixed" pattern because there is less consistency in the individual responses to the tasks. The more "physical" tasks such as cold pressor, hand grip exercise, and especially bicycle exercise produce a more similar pattern across individuals; the "mental" tasks are less consistent, perhaps due to differences in task appraisal and motivation.

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