Transforming Water: Social Influence Moderates …...Social Influence Moderates Placebo Response 2" Abstract Objective: The current study tests whether social influence can change

Social Influence Moderates Placebo Response 1

Transforming Water: Social Influence Moderates Placebo Response

Alia J. Crum1*, Damon J. Phillips3, E. Tory Higgins3

1Department of Psychology, Stanford University, Stanford, CA 94305

2Columbia Business School, Columbia University, New York, NY 10027

3Department of Psychology, Columbia University, New York, NY 10027

Key words: placebo, social-influence, caffeine, expectation, mindset

Correspondence to:

Dr. Alia J. Crum Bldg. 420, Jordan Hall, Rm 244 Stanford, CA 94305-2130 ph: 970 987 9182 email: [email protected]


Abstract

Objective: The current study tests whether social influence can change physiological and

functional responses to a faux product. Methods: After drinking bottled water under the

impression that it was caffeinated, participants reported feeling significantly more alert. There

was also an increase in typing speed and a decrease in cognitive interference. Most important,

subjective, physiological and functional effects of the faux product were greater for participants

paired with confederates who claimed they felt the caffeine effect than participants paired with

confederates who denied the effect. Moreover, the physiological effect of the faux caffeinated

water, which we liken to a placebo effect, mediated the likelihood of buying the product, as well

as the willingness to endorse the product to others. These results suggest that social influence can

alter subjective, physiological and behavioral responses to a faux product, thereby altering

attitudes toward the product.

Key Words: Social influence, placebo response, expectancies, consumer experience


Although we are told that “a rose by any other name would smell as sweet,” decades of

psychological research establishes that the sensory properties of an object are not the sole

determinant of how we experience it. Associations or expectations from how we describe the

object also matter. This is especially true for shaping experiences of food and beverage

consumption. For example, people enjoy the taste of Coke more when it is consumed in a brand

name cup (McClure et al., 2004), children enjoy the taste of French fries, milk, and carrots more

when they believe them to be from McDonalds (Robinson, Borzekowski, Matheson, & Kraemer,

2007), and beer infused with vinegar is enjoyed more if it is labeled as having a “special

ingredient” than when the actual ingredient is unveiled (Lee, Frederick, & Ariely, 2006).

Inspired by the neurological and physiological effects found in clinical trials and placebo

research (Finniss, Kaptchuk, Miller, & Benedetti, 2010), a growing body of research suggests

that, in addition to influencing perception and behavior, top-down processes can also alter

objective outcomes such as sensory experience and physiological processing. For example,

manipulating the perceived cost of wine to be more expensive (with the same wine) can result in

heightened activity in areas of the brain related to pleasure and reward (Plassmann, O’Doherty,

Shiv & Rangel, 2008). Individuals who thought they were drinking an indulgent, high-calorie

milkshake showed steeper declines in ghrelin, a hunger-inducing hormone, than when they

thought that the same shake was a sensible, low-calorie milkshake (Crum et al., 2011).

Such effects do not exist in a vacuum. Instead, social forces dynamically inform them.

Social forces supply new information, confirm or correct old information, and serve as a

foundational source for our mindsets, beliefs, and expectations (Asch, 1948; Robert B. Cialdini,

2005; Hardin & Higgins, 1996; Muchnik, Aral, & Taylor, 2013; Salganik, Dodds, & Watts,


2006). Individuals often turn to others for information about what foods are good or bad, what

diets work or fail, and what medications are most effective. Social forces can clearly change

subjective preferences or perception (R. B. Cialdini & Goldstein, 2004; Colloca & Benedetti,

2009; Moscovici, Lage, & Naffrechoux, 1969; Salganik et al., 2006; Sherif, 1937). In addition,

social information (e.g., about other’s attractiveness) can increase or decrease the neurological

activity in the orbitofrontal cortex and the nucleus accumbens, suggesting that social influence

can produce changes in brain areas corresponding to hedonic experience (Zaki, Schirmer, &

Mitchell, 2011). And some have suggested that consuming a product in the presence of another

person provides subtle non-verbal cues which can facilitate a synchronistic process in which

attitudes about the consumed substance converge (Ramanathan & McGill, 2007). But can social

influence literally “get under the skin” and affect physiological experiences of a product?

Literature from medical and placebo research suggests that this may indeed be possible.

Research on mass psychogenic illness (MPI) demonstrates that the collective occurrence of self-

reported physical symptoms in the absence of an identifiable pathogen is a relatively common

occurrence (Mazzoni, Foan, Hyland, & Kirsch, 2010). Studies exploring MPI empirically have

shown that the belief that one has inhaled a substance described as an environmental toxin (when

in fact just odorless ambient air) can evoke the experience of corresponding symptoms (e.g.,

headaches, nausea, itchy skin, and drowsiness). Most importantly, researchers have documented

that these symptoms are increased (up to an 11x increase in one study) when in the presence of a

confederate participant displaying the expected symptoms (Broderick, Kaplan-Liss, & Bass,

2011; Lorber, Mazzoni, & Kirsch, 2007; Mazzoni et al., 2010). In placebo analgesia research,

studies have demonstrated that in addition to traditional conditioning procedures, pain relief can

be conditioned by witnessing another person receive pain relief (Colloca & Benedetti, 2009).


Together, these studies suggest that social influence can engender a more visceral experience.

These studies are limited to a clinical context, however, and have only explored self-reported

experience of visceral sensations. Whether social influence can affect physiological and

functional responses in everyday experience has yet to be explored.

To test this question we created a fictional product, “AquaCharge Energy Water,” which

we claimed had 200 mg of performance and energy-enhancing caffeine but was, in reality, plain

spring water. After administering the product to participants we compared measures of

subjective arousal, physiological arousal and cognitive function known to respond to the effects

of caffeine across three conditions: a no confederate condition, in which the participant

consumed the water in a room alone, a disconfirming confederate condition, in which the

participant consumed the water alongside a confederate who denied the effect of the product, and

a confirming confederate condition, where the confederate participant endorsed the effect of the

product. We predicted that, in line with research on the effects of placebo caffeine, all

participants would experience increases in subjective, physiological and functional response

(Harrell & Juliano, 2009). Additionally, we predicted that in line with research on social

influence (e.g., Colloca & Benedetti, 2009) these effects would be moderated by social influence

such that they would increase in the presence of an affirming confederate and decrease in the

presence of a denying confederate. We also investigated whether attitudes toward the product

would be mediated by the effects on the subjective and physiological responses to the product.

Participants and Design

We recruited 134 females (24% Black, 40% White, 36% Asian) (mean age=24 years;

SD=5) from a university study pool. A sample size of at least 30 participants was determined in

advance. The decision to have at least 30 participants in each condition was based on previously


published research on MPI, placebo caffeine, and social influence (e.g., Mazzoni et al., 2010;

Boothby et al., 2010; Harrell & Juliano, 2009). Participants were screened at the onset and

excluded from the study if they were a smoker, had high blood pressure, or reported intake of

alcohol, antihistamines, caffeine, or anything besides water two hours prior to experiment.

Participants received $20 for their participation, with the opportunity to earn a $100 gift card

reward if they completed the one-week follow-up questionnaire. Participants were randomly

assigned to the following conditions: 1) no confederate condition (N = 35); 2) confirming

confederate condition (N= 59); or 3) disconfirming confederate condition (N = 41). To heighten

the effect of social influence (Echterhoff, Higgins, & Levine, 2009) and reduce variability from

gender effects on arousal (Hartley, Lovallo, & Whitsett, 2004) participants were matched to the

same-race and same-gender confederates.

Procedure

Participants were asked to not drink caffeine or consume anything except water for two

hours prior to the onset of the 1-hour study, which took place during the morning hours of 9am-

12pm. After arriving at the laboratory, participants filled out two short questionnaires. The first

assessed their caffeine exposure and expectancies (Harrell & Juliano, 2009) as well as their

subjective arousal levels (Kirsch & Weixel, 1988). Participants were then directed into a room

in which a same-race, same-gender confederate participant was present (condition 1 with

disconfirming confederate; condition 3 with confirming confederate) or into an empty room with

no other participant present (condition 2 with no confederate). The participant and (for

conditions 1 and 3) the confederate were then connected to a Noninvasive Blood Pressure

System (NIBPH100D) to record systolic blood pressure (SBP) responses. In order to assess their

baseline functional performance, they then completed a Stroop task (Stroop, 1935) and a finger


tapping psychomotor speed task (Fagan, Swift, & Tiplady, 1988). All measures were chosen

because of their established relationship to caffeine intake.

Following these baseline measurements, participants were given an iPad and asked to

view and rate the product’s website (Figure 1). The purpose of this was to add to the credibility

of the study guise (beta-testing the marketing for a new product) and ensure that the participants

paid attention to the placebo/mindset intervention (that the water is infused with caffeine and

thus will increase their arousal, energy and reaction time when consumed).

Figure 1. Screenshot of the AquaCharge website “The Buzz” page.

After completing the website-rating form, participants were given an 8 oz bottle of

AquaCharge (Figure 2) and asked to consume the product in its entirety within two minutes.

Participants were then told to wait “a few minutes for the energy water to take effect.” Three

minutes after consuming the water, the confederate participant spoke. In the disconfirming

confederate condition, the confederate stated: “Hmm. I don’t really feel any change. I’m

definitely NOT feeling charged up. How about you?” In the confirming confederate condition,


the confederate participant stated: “Wow! This is really something. This is really waking me up!

How about you?” The participant was given a few seconds to respond upon which the

experimenter entered the room and reminded participants to stay quiet during the testing phase.

For the next five minutes, participants sat quietly and completed a few questions asking about the

product label, taste of the product. These were filler questions designed to keep them focused on

the product and maintain alignment with the study guise.

Figure 2. Label affixed to 8oz plastic bottles of spring water.

Ten minutes after consuming the product, the participant completed the 15-item

subjective arousal questionnaire as well as post-consumption functional response tasks including

the Stroop and finger tapping tasks. Finally, they completed a “Product Endorsement Survey”

which asked participants to suggest a product cost, enroll to be a product ambassador, and

indicate their likelihood to purchase AquaCharge in the future.

After completing the experimental procedure, participants were unhooked from the

Noninvasive Blood Pressure System and paid $20 for their participation. One week later

participants were contacted by email and asked to fill out a short survey asking them how many

people they had told about the product and for what reasons.

Measures. Subjective, physiological and functional tasks were chosen based on research

supporting the effects of caffeine on subjective arousal (Childs & de Wit, 2006; Smith, 2002),


systolic blood pressure (Hartley et al., 2004; Karatzis et al., 2005) cognitive interference (Dixit,

Goyal, Thawani, & Vaney, 2012; Kenemans, Wieleman, Zeegers, & Verbaten, 1999) and

psychomotor speed (Heatherley, Hayward, Seers, & Rogers, 2005).

Subjective Arousal: Participants’ subjective arousal was measured by a scale developed

and validated by Kirsch & Weixel (Kirsch & Weixel, 1988) for the purposes of studying the

effects of caffeine. The scale includes fifteen adjectives along a 5 point Likert scale which factor

in three subscales indicating alertness, relaxation, and tension. In the current sample, Cronbach’s

alpha was adequate (alertness subscale alpha = .79; tense subscale alpha = .73; relaxation

subscale alpha = .86). There were no significant effects of time or condition for the tense or

relaxation subscales.

Physiological Arousal: Participants’ physiological arousal was measured using a

Noninvasive Blood Pressure System (NIBPH100D) that recorded systolic blood pressure (SBP)

responses. Once calibrated to the system, participants sat quietly for a 4-min baseline period.

Signals were examined offline; data were visually inspected for artifacts and then averaged in 1-

min segments using Mindware software (Gahanna, OH; Mendes, 2009) to determine PEP

reactivity, our measure of sympathetic activation. To equate in time with the subjective

responses we analyzed blood pressure at immediately before consumption and 5 minutes after

consumption. Due to technical issues with the blood pressure machine or excessive movement,

data from several participants was unreadable, thus blood pressure was analyzed for 79

participants (N = 22 Disconfirming Confederate; N=25 No Confederate; N=32 Confirming

Confederate).

Functional Response (Cognitive Interference): Because cognitive interference has shown

to be affected by caffeine intake, participants’ cognitive interference was measured using the


Stroop color-naming task (Stroop, 1935; Macleod, 1991) (Stroop, 1935). Participants were

instructed to indicate the font color of a letter string by pressing one of four appropriate color-

coded keys as quickly as possible. On incongruent trials a color word appeared in a font color

different from its semantic meaning (e.g., “BLUE” in red font), whereas confirming trails

displayed a color word that matched its font color (e.g., “BLUE” in blue font). Control trials

consisted of a string of “@”s in one of the four font colors. Participants completed 20 practice

and 90 experimental trials. Stroop interference scores were computed as the difference in

response latencies (in milliseconds) between incongruent and congruent trials, with higher scores

indicating greater cognitive depletion. Incorrect responses and latencies above 2000 ms and

below 200 ms were recoded as missing data.

Functional Response (Psychomotor Speed): The established finger-tapping task is a

measure of psychomotor speed that is sensitive to caffeine (Heatherley et al., 2005). To complete

the task participants were instructed to place their index and middle fingers on two adjacent keys

on the keyboard and tap each of the keys in alternate succession as fast as possible for 1 minute.

Performance was measured as the total number of keys pressed per minute.

Functional Response (Grip Strength Dynamometer Test). Participants were given a

dynamometer and were asked to apply as much grip pressure as possible using their dominant

hand. The maximum reading in kg was measured. Participants repeated the test three times, with

the highest recorded value serving as their measure of performance.

Product Endorsement: After consuming the water and completing the functional tasks,

participants were asked a variety of questions pertaining to their endorsement of the AquaCharge

product. Should Cost was measured by asking people, “How much would you pay for

AquaCharge Energy Water in a store?” They were given several benchmarks to assist them in


making their decision including Gatorade ($1.50), Poland Springs Water ($1.75) and Five Hour

Energy ($2.10). Probability of Buying the product was measured by asking participants to rate

“What is the likelihood you would BUY AquaCharge in a store,” on a Likert scale ranging from

1= Not at all to 7 = Extremely. Ambassador Initiative was measured by taking the mean rating

of participants’ likelihood to: “Become a College Ambassador for AquaCharge”, “Boost my

resume by working for AquaCharge”, and “Help make AquaCharge available on or near your

campus,” (1= Not at all, 4 = A little, 7 = Extremely) (Chronbach’s alpha for the three items was

.92).

Product Endorsement (one week follow-up): One week following their participation,

participants were contacted by email and asked to fill out a short survey asking them how many

people they had had told about the product and the reasons for telling them (e.g., because “I love

the product and want people to know about it”; “I am just a talker and tell everyone things”; “I

didn’t like the product and wanted them to know I didn’t like it”; “I thought it was an interesting

idea” or “I thought they would be interested in it”). Number of People Told was calculated as the

total number told either because they checked “I love the product and want people to know

about it” or “I thought they would be interested in the product.” They then chose whether they

wanted to be entered to win either a $100 gift card or an $80 gift card and a case of 30 bottles of

AquaCharge, serving as a behavioral measure of product endorsement. Chose AquaCharge over

Cash was calculated as the total number of participants choosing this second option (0 = no, 1=

yes) per condition. Figure 2 illustrates this number as a percentage of the total number of

respondents per condition. Data was analyzed for the 79 participants who completed this follow-

up survey (N = 28 disconfirming confederate; N=12 no confederate; N=38 confirming


confederate). Complete means and standard deviations for each dependent variable are detailed

in Table 2.

Results

To test whether the social influence condition moderated changes in subjective,

physiological, and functional response, a hierarchical regression model predicting post

consumption subjective alertness, physiological alertness (SBP), and functional response was

conducted with baseline levels entered in Step 1 and social influence condition (disconfirming

confederate=1, no confederate=2, confirming confederate=3) entered in Step 2. These results

indicate a significant effect of social influence condition on subjective alertness [β=.20,

t(134)=2.93 p=.004] as well as change in physiological alertness as measured by systolic blood

pressure [β=.15, t(76)=2.07 p=.04] (Table 1). Furthermore, there was a significant effect of

social influence condition on functional response as indicated by change on the Stroop task from

baseline to post-consumption [β=-.17, t(126)=-1.94 p=.05] and a marginally significant effect of

social influence on the change in the number of letters produced on the finger-tapping task from

baseline to post consumption [β=.06, t(134)=1.72 p =.08] (Figure 3). We did not find a

significant effect of condition on grip strength performance.

Table 1. Stepwise regression results for changes in subjective, physiological, and functional response Subjective

Alertness Systolic

Blood Pressure Cognitive

Interference Typing Speed

β R2 ∆R2 β R2 ∆R2 β R2 ∆R2 β R2 ∆R2 Step 1 .36** .36** .42** .42** .09** .09** .86** .86** Baseline .60** .65** .29** .93** Step 2 .40** .04** .45* .03* .11* .03* .87** .01+ Baseline .60** .63** .30** .93** Condition

.20* .18* -.17* .06+

Note. **p<.01 *p<.05 +p< .10


Figure 3.. Effect of condition on subjective alertness (A) physiological alertness (B),

reaction time (C) and cognitive interference (D).

(A) (B)

(C) (D)

Note. Error bars reflect standard +/- 1 SE. (A) and (B) illustrate subjective alertness and SBP at

post consumption levels. (C) and (D) illustrate changes in reaction time and cognitive

interference from pre- to post- consumption. Complete pre and post means are listed in Figure 4.


Linear regression also tested the effect of condition on product endorsement variables

(likelihood of purchasing, should cost, ambassador initiative, number of people told about

product, and choice of AquaCharge over cash). These results indicate a significant effect of

social influence condition on product endorsement as indicated by what participants thought the

product should cost [β=.28, t(131)=3.26 p=.001], likelihood to buy AquaCharge [β=.27, t(134)=

3.203 p=.002], willingness to be an ambassador for the product [β=.21, t(133)=2.68 p=.01], the

number of people told about the product at a 1 week follow-up [β=.18, t(77)= 1.62 p=.11] and

the extent to which participants chose the option to win AquaCharge over cash [β=.24,

t(77)=2.18 p=.03] (Figure 4).


Figure 4. Effect of condition on product endorsement. (A) (B)

(C) (D)

(E)

Note. Error bars reflect standard +/- 1 SE.


Table 2. Means and (standard deviations) for outcome variables as a function of condition

Condition Disconfirming Confederate

No Confederate

Confirming Confederate

Subjective Alertness Baseline 3.35(.62)a 3.34(.53)a 3.35(.68) a Post Consumption 3.58(.69) a 3.78(.52) ab 3.86(.59)b Change 0.22(.58) a 0.44(.49) b 0.51 (.55) b Systolic Blood Pressure Baseline 126.0(18.8) a 130.9(25.8) a 131.1(25.9) a Post Consumption 115(32.1) a 120.32(24.8) a 130.6(27.6) b Change -11.0(33.13) a -10.6(14.07) a -0.50(17.21) b Typing Speed Baseline 431.00(117.36) a 427.23(89.34) a 424.39(98.53) a Post Consumption 442.19(111.60) a 446.80(80.20) a 448.71(89.47) a Change 11.19(36.96) a 19.57(23.81) a b 24.31(43.18) b Cognitive Interference Baseline 85.37(86.70) a 81.61(130.02) a 98.33(97.62) a Post Consumption 98.70(87.78) a 59.70(68.67) b 68.80(80.21) c Change 13.32(91.50) a -21.90(129.1) b -29.52(111.1) b Should Cost 1.60(.41) a 1.77(.41) b 1.88 (.42) b Probability of Buying 3.24(1.79) a 3.59(2.12) a 4.44(1.83) b Ambassador Initiative 2.39(1.66) a 2.36(1.78) a 3.27(1.93) b Listed Emails .09(.30) a .17(.38) b .27(.44) c Chose ACW over Cash* 1.11(.32) a 1.08(.29) b 1.32(.47) c # of People Told* .25(.97) a .08(.28) b .76(1.68) a

Note: Within a row, means with different subscripts differ at p < .05. * indicates measure taken 1 week after experiment.


We were curious to see whether the social influence effect on product endorsement was

mediated through differences in SBP, subjective alertness, or both, so we employed a

bootstrapping method (MacKinnon, Lockwood, Hoffman, West, & Sheets, 2002; Preacher &

Hayes, 2004) with n=5000 bootstrap resamples in which subjective alertness and SBP were

included as potential mediators in the model, and baseline alertness and pre consumption SBP

were included as covariates. Because the product endorsement variables hung well together

(alpha=.68) we created an aggregate index by taking the mean of the standardized variables. The

analyses revealed with 95% confidence that the effect of social influence on aggregate product

endorsement was significantly mediated by changes in SBP [point estimate=.04; 95% CI .0004,

.1110] and not by changes in subjective alertness [point estimate=.03 ; 95% CI .-.0073, .1463]

(Figure 3). This suggests that endorsement of the product was largely driven by the changes in

systolic blood pressure evoked by social influence rather than by changes in self-report

measures.


Figure 5. Graphic representation of mediation results including multiple mediators (5000

bootstrap samples).

(A)

Note. The effect of condition on probability of buying (A) and ambassador initiative (B) were

fully mediated by changes in systolic blood pressure (SBP) (point estimate < .05) and not by

changes in subjective alertness (point estimates > .05). + p < .01, * p < .05, ** p < .01.

Change in SBP

Condition Aggregate Endorsement

.06* .59*

.27**(.06*)

Change in Subjective Alertness

.10 .31*


Discussion

When participants entered our lab they thought they were drinking the latest in a line of

enriched bottled waters commonly appearing on the market. They believed that they were

drinking water infused with caffeine, when in fact it was just plain water. Despite the simplicity

of the substance participants reported feeling more alert, and they improved functionally (as

illustrated by an increase in typing speed and a decrease in cognitive interference). These effects

mimic what is commonly referred to as the placebo response in medicine. Most interestingly,

social influence moderated the strength of this effect—increasing it when the confederate

endorsed the effect and decreasing it when the confederate denied the effect. These results go

beyond previous research by suggesting that even in an everyday product interaction, social

influence can significantly alter an individual’s physiological and functional response to a

product. They suggest that to understand the true effects of any product or substance we must

understand and account for the psycho-social setting in which it is consumed. Moreover, the

social influence has long-term consequences, with participants not only being willing to pay

more for the product, more likely to buy it, and more likely to choose the product over cash, but

also being more interested in being an ambassador for the product and more likely to tell their

friends about the product.

Researchers have traditionally struggled to distinguish the effects of social influence on

true changes in preference versus mere public compliance (R. B. Cialdini & Goldstein, 2004;

Moscovici et al., 1969; Sherif, 1937). Recent research has informed this debate by employing

neurological techniques that suggest that social influence can produce changes in brain areas

corresponding to hedonic experience (Zaki et al., 2011). Our results suggest that social influence


can also produce physiological and functional responses, such as changes in systolic blood

pressure and cognitive speed in response to a faux stimulant. Moreover, our mediation results

suggest that endorsements of a product or substance may not simply be driven by social

influence or subjective reports of effectiveness. Instead, they seem to be most strongly driven by

physiological differences (in this case systolic blood pressure) induced by the social-

psychological nature of the experience.

This study also informs and expands upon the small but growing body of research in the

medical and placebo literatures that have documented the power of social modeling on placebo

responding (Colloca & Benedetti, 2009; Mazzoni et al., 2010). It extends this body of literature

by demonstrating that such effects can have a physiological and functional impact in addition to

self-reported effects and it suggests that social influence’s role on placebo effects need not be

limited to a clinical setting. Patients are not only influenced by the beliefs and expectations of

their doctor, nurse, or caretaker but also by friends, family, and peer-patients who share or have

shared the same conditions, medications, and treatments. While much of the science practice of

medicine aims to parse out the effects of non-specific or social-psychological factors, the results

herein suggest that such factors should not be seen as superfluous but, instead, as an active

ingredient in clinical care.

Several questions remain. First, how did the presence of a confederate participant

influence physiological or functional responding? Although it is possible that there was an

influence from the mere presence of the confederate (Zajonc, 1965); (Mazzoni et al., 2010), the

same presence of a confederate either increased or decreased the effects depending on what the

confederate said about the product experience. Given this, a more likely mechanism is that what

the confederate said about the product experience altered the response expectancies of the


participant, which in-turn influenced the participant’s physiological and functional responding.

In the current study, we did not measure the momentary change in expectations because we were

concerned that asking participants about their expectations after the social encounter could lead

them to question the study guise. Thus, more research is needed to thoroughly understand the

precise mechanisms through which social influence can affect physiological and functional

responding.

Second, what are the boundaries of these effects? In the current study we chose to study

women only and to match the race of the confederate with the participant to reduce variability

and maximize perceived similarity between the participant and the confederate. We used live

confederates matched with participants’ gender and race. According to Bandura’s Social

Learning Theory, male subjects are more prone to imitate male models and female subjects more

prone to imitate female models (Bandura, Ross, & Ross, 1961; Bussey & Bandura, 1984).

Research exploring social modeling on placebo responding has shown mixed effects of gender,

with some studies demonstrating greater effects with matched confederates (Lorber et al., 2007;

Mazzoni et al., 2010), and some demonstrating greater effects with male models (as in the case

of pain and placebo analgesia (Świder & Bąbel, 2013) and some showing no gender differences

in responding or matching affect (Broderick et al., 2011). The present study is limited in its

ability to inform this debate and or make claims outside of female-female interactions.

What about the form through which social information is communicated? In today’s

world, social influence is often transmuted through technology (via smartphone, email, etc.). Do

different communication means have the same effect? Hunter and colleagues (2014)

demonstrated the social modeling of a placebo analgesic is effective both when presented in

person as well as when participants view a recording of a participant (Hunter, Siess, & Colloca,


2014). However, more work is needed to understand the context in which social influence is

likely to have the most potent effect on individual experience.

Fourth, what is the relative weight of impact from social influence and objective qualities

of a product, substance, or experience? We intentionally chose water as our portal of choice,

rather than something like decaf coffee, in an effort to isolate the effect of social influence from

conditioning or other effects that might result from the smell of decaf coffee (Benedetti, 2008).

Future research is needed to understand how social influence interacts with sensory properties to

engineer the ultimate impact of a product, medication, or experience.

Though much remains to be explored, our results are intriguing in demonstrating that

social influence—working hand in hand with the psychological construction of sensory input—

can alter physiological and functional response to a product, in this case changing the experience

of, and attitudes toward, simple water.

Acknowledgments

We thank Nana Amoh, Hayley Blunden, Ellen Hada, and Yael Warach for their assistance in

conducting this experiment and our colleagues Jennifer Aaker, Ted Kaptchuk, Irving Kirsch,

Stephen Kosslyn and Jamil Zaki for their comments on this manuscript.

Author Contributions

A.J. Crum and D. J. Phillips developed the study concept. All authors developed the study design

and contributed to data analyses and interpretation. Data collection and data entry were

performed by research assistants under the supervision of A.J. Crum. A.J. Crum drafted the


manuscript and D. J. Phillips and E.T. Higgins provided numerous critical revisions. All authors

approved the final version of the manuscript for submission.

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Transforming Water: Social Influence Moderates …...Social Influence Moderates Placebo Response 2" Abstract Objective: The current study tests whether social influence can change