Affective data acquisition technologies in survey research

Abstract

There is no agreement on how to formally incorporate affective data into statistical analysis and research conclusions. The information systems (IS) literature has recently published several position papers that have established a framework and perspective for using affective technology in IS research though. The frameworks have not been extensively tested, and are likely to evolve over time as empirical studies are conducted, and the validity of the methodologies is confirmed or disproved. A major goal of the current paper is to take the initial steps in translating the frameworks to usable methodologies, with application to improving our understanding of how to make effective empirical tests. This paper also investigates the adoption cycle of one of these technologies—electrodermal response (EDR) technologies—whose incarnation in the polygraph in forensic applications went through a complete adoption cycle in the twentieth century. The use of EDR response data in marketing research and surveys is nascent, but prior experience can help us to forecast and encourage its adoption in new research contexts. This research investigates three key questions: (1) What technology adoption model is appropriate for electrodermal response technology in forensic science? (2) What is the accuracy of affective electrodermal response readings? (3) What information is useful after superimposing affective EDR readings on contemporaneous survey data collection? Affective data acquisition technologies appear to add the most information when survey subjects are inclined to lie and have strong emotional feelings. Such data streams are informative, non-invasive and cost-effective. Informativeness is context-dependent though, and it relies on a complex set of still poorly understood human factors. Survey protocols and statistical analysis methods need to be developed to address these challenges.

Appendices

Appendix 1

See Table 11.

Table 11 Table of terms and definitions

Appendix 2: Sweat glands, emotional responses and conductivity

The eccrine sweat glands are around 3.5 mm in length, with a pore size of 0.05–0.07 mm (for comparison, the diameter of a human hair is around 0.08–0.1 mm in diameter). Each pore sits on top of a palmar fingerprint ridge. Their purpose is to provide a liquid cooling system for the exterior of the human body. The eccrine sweat glands have three primary functions:

• Thermoregulation. Sweat cools the surface of the skin and reduces body temperature. This cooling is the primary function of sensible perspiration, and the degree of secretory activity is regulated by neural and hormonal mechanisms. When all of the eccrine sweat glands are working at maximum, the rate of perspiration may exceed a gallon per hour, and dangerous fluid and electrolyte losses can occur. For this reason, athletes in endurance sports must pause frequently to drink fluids. In general, this type of thermoregulatory sweating is not linked to emotional state.

• Excretion. Eccrine sweat gland secretion can also provide a significant excretory route for water and electrolytes, as well as for a number of prescription and nonprescription drugs.

• Protection. Eccrine sweat gland secretion provides protection from environmental hazards by diluting harmful chemicals and discouraging growth of microorganisms.

Stress, anxiety and socially unpleasant situations can cause the hands to sweat because of the secretion of sympathetic-like materials and hormones (mediators) from different organs in the body. Emotional factors, such as a sudden shock or a feeling of impending danger, can effectively trick the body into reacting as if there is an external rise in temperature that would threaten the temperature of the body. This phenomenon can occur during periods of intense fear, or begin to function in the aftermath of a crisis situation. This response is controlled by sympathetic cholinergic nerves controlled by a center in the hypothalamus. The hypothalamus senses core temperature directly, and also has input from temperature receptors in the skin. It modifies the sweat output, along with other thermoregulatory processes.

Hand sweating beyond that needed for temperature regulation is linked to high levels of activity or stress in the sympathetic nervous system. In cases of palmar hyperhidrosis or hand sweating, the responsible sympathetic ganglia are located within the upper part of the chest cavity. In cases of plantar hyperhidrosis or foot sweating, the responsible sympathetic ganglia are located within a section of the lumbar sympathetic chain. In general, this type of temperature-initiated sweating is not linked to emotional state.

Stimulation of eccrine sweat production is mediated through postganglionic C fiber production of acetylcholine. Emotional stressors tend to induce sweating that is confined mainly to the palms and soles. All eccrine units can be utilized to respond to the body’s changing thermoregulatory needs. Eccrine sweating is controlled by the anterior hypothalamic nucleus in the brain, in a part of the hypothalamus, whose functions control thermoregulation panting, sweating, and thyrotropin inhibition.

There are many neural pathways throughout the hypothalamus, and overall, the hypothalamus is responsive to: light, especially the day length and photoperiod for regulating circadian and seasonal rhythms; olfactory stimuli, including pheromones; and steroids, including gonadal steroids and corticosteroids. It also is sensitive to neutrally-transmitted information from the heart, the stomach, and the reproductive tract; autonomic inputs from other parts of the body; blood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose; and invading microorganisms by increasing body temperature, resetting the body’s thermostat upward. A final key source of stimulation is human stress.

Human eccrine sweat is produced in the coiled gland, and then it travels up to the surface through the eccrine duct. It is composed chiefly of water with various salts and organic compounds in solution. It contains minute amounts of fatty materials, urea, and other wastes. The concentration of sodium varies from 20 to 38 g/kg (~35–65 mmol/l or about 2.0–3.8% concentration; almost exactly the same concentration of salt in seawater) and is lower in people accustomed to a hot environment. Sweat’s conductivity is linearly dependent on ion concentration.

The coiled gland is located in the deep dermis or at the border of the dermis and subcutaneous fat. It is composed of one distinct layer of clear and dark cells. The clear cells secrete glycogen, water, and electrolytes—which are responsible for the resistance changes measured by the electrodermal response mechanisms—and the dark cells secrete sialomucin. These secretory cells are surrounded by contractile myoepithelial cells enclosed within a hyaline basement membrane with peripheral collagen fibers. The contractile myoepithelial cells are made of alpha smooth muscle actin and can contract and quickly expel the secretions of the sweat glands. Direct neural stimulation of the contractile myoepithelial cells can change the skin conductivity within hundredths of a second, and can be responsible for the very quick responses seen in the electrodermal response readings. Slower cycles in resistance may be due to the general excitation resulting from the diffusion of hormones, but are a result of the same contractions. Because the eccrine sweat glands are small and distances are short, they can change the contact resistance very quickly in response to neural impulses, or less quickly to diffusion of hormones and neuro-transmitters. This change in pore size is called the sympathetic skin response [27] and is strongly influenced by the body’s thermoregulation and homeostasis mechanisms.

The conductivity of a solution is the inverse of its resistance, G = 1/R. The shape of the conductor affects conductivity values, standardized measurements are expressed in specific conductivity units (Siemens/cm) to compensate for variations in electrode dimensions. Specific conductivity σ = G (L/A), where L is the length of the column of liquid between the electrode and A is the area of the electrodes. See Table 12. Sweat is not a great conductor but has much higher conductivity than fat or other tissue, or than that of the stratum corneum of the palm. Thus, any saltwater sweat pathway through the eccrine ducts will essentially short the contacts on the outside of the epidermis to the conductive tissue in the body.

Table 12 Specific conductivity of saltwater at atmospheric pressure in Seimens/meter

In the case of cylindrical handheld electrodes of traditional electrodermal response machines, the stratum corneum may be seen as a large flat insulating layer (dielectric with resistance above 1 megaohm when dry, but usually 50,000–100,000 ohms due to residual moisture retained in the keratin) with an electrode on each side (the 300–1,000 ohms resistance of the inner tissues being comparatively conductive). Any layer of sweat on the palms will be flattened by a handheld electrode. The eccrine gland can be thought of as a tube of ionized saltwater extending through the eccrine duct to the more conductive tissues underneath. The eccrine ducts are about 3.5 mm long by 0.05 mm wide at maximum, for a cell constant of about L/A ≈ 1,400,000/m. Conductivity for a single sweat gland will be the specific conductivity of saltwater at a sweat concentration of 35 g/kg for a body temperature of 37° (≈6.424) divided by this cell constant, for a measured conductivity of G = σ/(L/A) = 6.424/1,400,000 ≈ 0.00000458857. This corresponds to a measured minimum resistance of 1/G = 217,933 ohms across a single eccrine duct. Since parallel conductances like those of adjacent sweat ducts can simply be added, we can sum over the total number of conducting sweat glands to get the total conductivity. See Table 13.

Table 13 Specific conductivity of sweat and other common substances

Resistance drops dramatically as soon as a few eccrine sweat ducts open and fill with sweat; that resistance can just as quickly raise as the contractile myoepithelial cells, under the direction of the autonomic nervous system and the anterior hypothalamic nucleus, contract and cut-off the circuit. There are around 420 eccrine sweat glands per square centimeter on the palms, and a total of about 100 cm² on each palm. So there are about 84,000 eccrine sweat ducts on the two hands together. Resistance between cylindrical handheld electrodes can, as a result of stress, quickly shift from the inherent greater than 50,000 ohm resistance of the dry epidermis to near 0, which explains the sensitivity of polygraph machines to human stress.

Another way of visualizing the change in resistance is to assume that all of the pores are equally dilated, and that this dilation is somehow related to the level of excitation or stress. Assume that a particular stress level γ results in the diameter of the pore being some percentage of its 0.05 mm full dilation. We will call this the proportion. Then 0.05 δ ∝ γ. Greater stress will contract the myoepithelial cells at the base of the eccrine duct, and secrete the saltwater to the surface of the palm ridge. In this scenario, the 84,000 eccrine sweat ducts on the two hands together are all about 3.5 mm long by 0.05 mm × δ, and L/A ≈ and (1,400,000/δ ²)/m, for a measured conductivity of G = δ (L/A) = (6.424δ ²)/1,400,000 ≈ 0.000004588757 × 84,000 × δ ², which corresponds to a measured resistance of 1/G = 2.59/δ ² ohms across a single eccrine duct.

Appendix 3: Synopsis of the survey

Objective of the survey. The current United States political climate is sufficiently polarized and publicized to assure that the top political stances are likely to elicit emotional responses from a wide cross-section of its population. The following survey paraphrases political positions taken by the two candidates in the 2008 presidential election, culled from a Washington Post poll called “Choose Your Candidate.” This source provides information on the breadth of political positions taken by the two candidates in the 2008 presidential election. Its source is www.washingtonpost.com/wp-srv/politics/interactives/candidatequiz. This opinion research seeks to identify prevailing voter opinions on the top issues in 2010: the economy, family values, gun control; immigration, and the Middle East War.

Statements for agreement or disagreement. The statements are grouped into these five particular topics. The scaling can be done differently on how the questions are worded. We use a Likert scale which runs from 0 = strongly disagree to 7 = strongly agree. The statements are as follows:

• 1. (I) I am now in Chicago.

• 2. (S ₁) I am a conservative, and I tend to vote for either a Republican or Independent ticket.

• 3. (P ₁) Only the wealthiest Americans benefit from the current economic growth; all Americans do not benefit equally from an expanding economy.

• 4. (P ₁) To promote economic growth and prosperity, we must keep spending under control and taxes low, open markets for American goods and services, and have a strong technology industry.

• 5. (T) I have lied to a public official, for example, a police officer.

• 6. (S ₂) I believe in minimal government, low taxes, and that everyone is responsible for the consequences of their actions and life choices.

• 7. (P ₅) Our top national security priority should be defeating radical Islamic extremists, breaking our dependency on foreign oil, and pushing for a worldwide League of Democracies.

• 8. (T) In my current or prior employment, I have stolen office supplies, and used office services, such as telephone or copier services. that should be restricted to business use.

• 9. (P ₅) believe that, as long as we have a chance to succeed, we must try to succeed in Iraq and Afghanistan.

• 10. (P ₄) I want to toughen security at our borders, place stronger restrictions or sanctions on employers hiring illegal immigrants, and provide a path to earned citizenship.

• 11. (P ₂) I support same sex marriages, and if the Supreme Court should ever strike down state or local laws designed to protect the traditional family, I would support a Constitutions amendment to define the family as a union between one man and one woman.

• 12. (T) In my current or prior employment, I have been justified in lying to my supervisor.

• 13. (P ₂) I believe we should ban funding for embryonic stem cell research and make it a federal crime for researchers to use cells or fetal tissue from an embryo created for research purposes.

• 14. (P ₁) The federal government should seek to end poverty in the U.S., and should increase spending on anti-poverty programs.

• 15. (S ₃) I consider myself a liberal, and tend to vote for either a Democratic or Independent ticket.

• 16. (P ₃) You should not tamper with the Second Amendment right to keep and bear arms; it is a law-abiding citizen’s right to own guns.

• 17. (I) The lights are on in this room.

• 18. (P ₂) I support Roe v. Wade and believe that abortion should be safe, legal and rare.

• 19. (P ₃) I support instant criminal background checks to allow the immediate purchase of a firearm.

• 20. (S ₄) I believe that social welfare programs are justified, because they help those who can’t help themselves.

• 21. (P ₅) We should begin withdrawal of all our overseas troops from Iraq to Afghanistan immediately.

• 22. (P ₄) I support affirmative action for all minorities and immigrants through plans that result in quotas, where such plans have been judicially created to remedy a specific, proven act of discrimination.

• 23. (P ₄) Parents should be empowered with school choice to send their children to the school that can best educate them.

• 24. (P ₅) We cannot react to past mistakes by beginning troop withdrawals; our previous strategy of a partial troop pullback was an even greater mistake.

• 25. (P ₃) Gun control measures reduce violent crime and save lives.

• 26. (P ₁) We should keep income taxes low by making existing tax cuts permanent and eliminating the threat of a crippling tax increase in the coming years.

• 27. (P ₃) Tighter restrictions should be in place for buying a firearm.

• 28. (S ₅) War is justified when it protects real or potential threats to national security.

• 29. (I) There are 24 h in a day.

• 30. (P ₂) I believe that states must be legally bound to recognize same sex marriages and unions.

• 31. (P ₄) Our top priorities with regard to immigration should be to secure the U.S. border, and restore the trust Americans should have in the basic competency of their governments to enforce the law. Illegal immigrants are a threat to our security, economy and American traditions.

• 32. (P ₅) I believe that, as long as we have a chance to succeed, we must try to succeed in Iraq and Afghanistan.

Statement types. The codes in brackets to the left of each statement have a letter code (below) and a number code (related to the topic above):

• I: Irrelevant statements are worded so the answer is 6–7 = strongly agree. These will include the very first statement as well as two others in the center of the survey instrument. Irrelevant statements are designed to identify the subject who are obviously “gaming” the survey, and who are not serious.

• T: Truthfulness statements are Statements 5, 7 and 12. They involve behavior that the majority of subjects have been involved in. Thus, when the subject answers 1–3 = disagree, this is probably a lie. Comparison statements are designed to identify the subject who is “gaming” the survey.

• S: Sacrificial statements always immediately precede the first of the set of three statements eliciting information on a particular topic. It is worded so that the subject answer is 5–7 = agree. These are designed to absorb the initial response to a relevant issue and to set the context so that subsequent statements on the same issue are recognized, and elicit consistent responses. They are not included in the evaluation/conclusions.

• P: Primary relevant statements are those that are information bearing, and provide information used in drawing conclusions from the study.

This information is summarized in Table 14.

Table 14 The survey’s statement types