The Economic and Cognitive Effects of Physical Pain among Low-Income Workers in India

Last registered on August 18, 2018


Trial Information

General Information

The Economic and Cognitive Effects of Physical Pain among Low-Income Workers in India
Initial registration date
June 24, 2017

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
June 26, 2017, 10:03 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
August 18, 2018, 11:17 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

MIT Economics

Other Primary Investigator(s)

PI Affiliation
University of Chicago, Booth School of Business
PI Affiliation
Harvard University
PI Affiliation
University of Pennsylvania
PI Affiliation
University of Pennsylvania

Additional Trial Information

Start date
End date
Secondary IDs
Physical pain is a common but largely overlooked aspect of the lives of the poor. Not only does pain directly reduce life quality and happiness, it may also hamper cognitive function and, consequently, decision-making, productivity, and earnings. Workers with chronic pain may work fewer days, take longer breaks, and make less-considered choices regarding inputs; all outcomes that would reduce output and lead to greater impoverishment or impede the productivity and profitability of microenterprises and firms. We will take the first steps in understanding the broader causal impact of physical pain on the cognitive and economic lives of the poor via a randomized controlled trial (RCT). 450 low-income women in Chennai, India, will be assigned to one of three treatment arms: 600 mg of over-the-counter pain medication, a placebo pill, or no medication. The research will quantify the causal impact of reduced pain on previously unstudied outcomes essential to escaping poverty including cognitive function, productivity, and earnings.
External Link(s)

Registration Citation

Dean, Emma et al. 2018. "The Economic and Cognitive Effects of Physical Pain among Low-Income Workers in India." AEA RCT Registry. August 18.
Former Citation
Dean, Emma et al. 2018. "The Economic and Cognitive Effects of Physical Pain among Low-Income Workers in India." AEA RCT Registry. August 18.
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Experimental Details


We propose to evaluate the effect of reductions in chronic physical pain on cognitive function and productivity among poor individuals via a simple intervention using over-the-counter (OTC) pain medication. To do this, we will enroll 450 low-wage female workers in Chennai, India into a two-day randomized controlled trial in which 150 randomly selected participants will receive OTC Non-steroidal Anti-inflammatory Drugs (NSAIDs; namely, Ibuprofen) at FDA-approved levels of one dose of 600 mg each on a single day, 150 participants will receive a placebo pill, and 150 participants will serve as a no-treatment control group.

Participants will complete a detailed survey, a battery of cognitive tests, pain measurements, a task to objectively scale each participant’s pain assessments, and a task designed to measure economic productivity as detailed below.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
(1) A comprehensive survey will elicit information about demographics, income and labor supply, subjective well-being, measures of past and current physical pain (e.g. location, intensity, and frequency), coping strategies, and reported impacts of pain on productivity. This data will be use to provide context and to control for baseline characteristics of the participants. This survey is conducted on the first day.

(2) Cognitive function will be assessed by conducting a battery of standard cognitive tasks each completed three times -- once on the first day of the study (to familiarize participants with the tasks), again the morning of the second day (before any treatment), and again in the afternoon (after taking the NSAIDs or placebos for those in the treatment arms). These tasks (Hearts and Flowers, N-back, Raven’s Matrices, and Corsi block-span) are all validated measures used in medicine and cognitive psychology (Davidson et al. 2006; Diamond et al. 2007; Raven 1936, 2000; Jaeggi et al. 2008). These tasks are compensated according to performance.

(3) Pain levels will be measured via a visual analog scale commonly used for such measurements in the pain literature. In addition, we will improve upon this traditional measurement of pain by measuring participant’s pain tolerance via the Cold Pressor task, often used in the psychology literature. This task incentivizes each participant to place and hold his or her hand in very cold water as we elicit pain levels at pre-specified intervals in order to observe pain levels change over time.

(4) Our productivity measure closely resembles participants’ daily work; individuals are provided with input materials and given 30 minutes in the morning (serving as a baseline/pre-treatment measure of productivity) and 3 hours in the afternoon (the outcome of interest) of the second day to string flowers at the study office. Participants are paid based on the weight of flowers strung and given half of the product of their work upon completing the study. Measured outcome variables include weight and length of flowers strung in the time given, as well as an independent assessment of stringing quality by two flower stringers who are not participants and who are blind to the treatment assignment.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Study location:
The study will be based at the Behavioral and Development Economics Lab in Chennai, India, founded by PIs Schofield and Schilbach in conjunction with a local institution, the Institute for Financial Management and Research (IFMR).

Participants will consist of female flower stringers in Chennai, India. Flower stringers are self-employed individuals typically working on the streets. These women purchase flowers in the morning, string them together, and sell the strands to customers passing by. Their average daily income is Rs. 250-500 (approximately $4-9). Preliminary survey evidence suggests a higher prevalence of physical pain among older individuals; hence, this study will limit enrollment to individuals aged 25 to 65 years. We focus on this population for several additional reasons. First, the nature of their work (stringing flowers while sitting on the floor for most of the day) causes high levels of pain. Second, due to the societal norms in the area, women do not regularly consume significant amounts of alcohol, substantially lowering the risks associated with taking pain medication. Third, the nature of their work makes flower stringers’ productivity easily measurable (length and weight of flowers strung). Finally, although this population is specific, participants are similar in many ways (e.g. age, education, labor habits) to many workers in the informal sector, improving the study’s external validity.

Recruitment and screening:
Surveyors approach potential participants at their place of work (typically a stand on the side of the street). The surveyor shares information about the study, while also conducting a broad first screen for eligibility. If participants are interested in participating and pass the initial screening, they schedule a time to come in to the lab for Day 1 (see below for further detail on the timing of the study). On Day 1, all potential participants are further screened to ensure: 1) their primary profession is flower-stringing, 2) they do not have any health conditions which are contraindicated for taking ibuprofen, 3) they regularly experience pain from their work, and 4) they are between the ages of 25 and 65.

Day 1: Following field recruitment, potential participants are screened for eligibility and complete an informed consent process. If eligible, participants complete the survey measuring demographics, work habits, and data on the type and amount of pain typically experienced. Participants also complete the battery of cognitive assessments.

Day 2: Participants complete the battery of cognitive tasks and 30 minutes of flower stringing in the morning (pre-treatment). Participants report their pain levels periodically and complete a "pain calibration" by reporting their pain levels while holding their hand in cold water. They are then randomly assigned to one of the three experimental arms at lunch. After lunch, all participants complete another 3 hours of flower-stringing and repeat the battery of cognitive tasks. Participants also complete a "pain tolerance test" after lunch. In this task, participants are paid for the time they leave their hand in cold water.
Experimental Design Details
Randomization Method
We will randomize using Stata and then reveal the experimental condition assignment to individuals privately. Any non-compliance will be carefully tracked.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
450 individuals
Sample size (or number of clusters) by treatment arms
150 control participants, 150 placebo participants, 150 ibuprofen participants
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
3.7% (SD of 42g) for weight of flowers strung. 2.1% (SD of Rs. 11.6) for payment for performance on cognitive tasks (which are compensated according to performance).

Institutional Review Boards (IRBs)

IRB Name
IFMR Human Subjects Committee
IRB Approval Date
IRB Approval Number
IRB Name
MIT Committee on the Use of Humans as Experimental Subjects
IRB Approval Date
IRB Approval Number


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