Crowdsourcing for Human ComputerInteraction ResearchEd H. ChiResearch ScientistGoogle(work done while at [Xerox] PARC with Aniket Kittur)
User studies• Getting input from users is important in HCI – surveys – rapid prototyping – usability tests – cognitive walkthroughs – performance measures – quantitative ratings
User studies• Getting input from users is expensive – Time costs – Monetary costs• Often have to trade off costs with sample size
Online solutions• Online user surveys• Remote usability testing• Online experiments• But still have difficulties – Rely on practitioner for recruiting participants – Limited pool of participants
Crowdsourcing• Make tasks available for anyone online to complete• Quickly access a large user pool, collect data, and compensate users• Example: NASA Clickworkers – 100k+ volunteers identified Mars craters from space photographs – Aggregate results virtually indistinguishable from expert geologists experts crowds http://clickworkers.arc.nasa.gov
Amazon s Mechanical turk• Market for human intelligence tasks• Typically short, objective tasks – Tag an image – Find a webpage – Evaluate relevance of search results• Users complete for a few pennies each
Using Mechanical Turk for user studies Traditional user Mechanical Turk studiesTask complexity Complex Simple Long ShortTask subjectivity Subjective Objective Opinions VerifiableUser information Targeted demographics Unknown demographics High interactivity Limited interactivity Can Mechanical Turk be usefully used for user studies?
Task• Assess quality of Wikipedia articles• Started with ratings from expert Wikipedians – 14 articles (e.g., Germany , Noam Chomsky ) – 7-point scale• Can we get matching ratings with mechanical turk?
Experiment 1• Rate articles on 7-point scales: – Well written – Factually accurate – Overall quality• Free-text input: – What improvements does the article need?• Paid $0.05 each
Experiment 1: Good news• 58 users made 210 ratings (15 per article) – $10.50 total• Fast results – 44% within a day, 100% within two days – Many completed within minutes
Experiment 1: Bad news• Correlation between turkers and Wikipedians only marginally significant (r=.50, p=.07)• Worse, 59% potentially invalid responses Experiment 1 Invalid 49% comments <1 min 31% responses• Nearly 75% of these done by only 8 users
Not a good start• Summary of Experiment 1: – Only marginal correlation with experts. – Heavy gaming of the system by a minority• Possible Response: – Can make sure these gamers are not rewarded – Ban them from doing your hits in the future – Create a reputation system [Delores Lab]• Can we change how we collect user input ?
Design changes• Use verifiable questions to signal monitoring – How many sections does the article have? – How many images does the article have? – How many references does the article have?
Design changes• Use verifiable questions to signal monitoring• Make malicious answers as high cost as good-faith answers – Provide 4-6 keywords that would give someone a good summary of the contents of the article
Design changes• Use verifiable questions to signal monitoring• Make malicious answers as high cost as good-faith answers• Make verifiable answers useful for completing task – Used tasks similar to how Wikipedians described evaluating quality (organization, presentation, references)
Design changes• Use verifiable questions to signal monitoring• Make malicious answers as high cost as good-faith answers• Make verifiable answers useful for completing task• Put verifiable tasks before subjective responses – First do objective tasks and summarization – Only then evaluate subjective quality – Ecological validity?
Experiment 2: Results • 124 users provided 277 ratings (~20 per article) • Significant positive correlation with Wikipedians (r=. 66, p=.01) • Smaller proportion malicious responses • Increased time on task Experiment 1 Experiment 2 Invalid 49% 3%comments <1 min 31% 7%responsesMedian time 1:30 4:06
Generalizing to other user studies• Combine objective and subjective questions – Rapid prototyping: ask verifiable questions about content/design of prototype before subjective evaluation – User surveys: ask common-knowledge questions before asking for opinions
Limitations of mechanical turk• No control of users environment – Potential for different browsers, physical distractions – General problem with online experimentation• Not designed for user studies – Difficult to do between-subjects design – Involves some programming• Users – Uncertainty about user demographics, expertise
Quick Summary• Mechanical Turk offers the practitioner a way to access a large user pool and quickly collect data at low cost• Good results require careful task design 1. Use verifiable questions to signal monitoring 2. Make malicious answers as high cost as good-faith answers 3. Make verifiable answers useful for completing task 4. Put verifiable tasks before subjective responses
Crowdsourcing for HCI Research• Does my interface/visualization work? – WikiDashboard: transparency visualization for Wikipedia – J. Heer’s work at Stanford at looking at perceptual effects• Coding of large amount of user data – What is a question? In Twitter, Sharoda Paul at PARC• Decompose tasks into smaller tasks – Digital Taylorism – Frederick Winslow Taylor (1856-1915) 1911 book Principles Of Scientific Management• Incentive mechanisms – Intrinsic vs. Extrinsic rewards – Games vs. Pay
What is Wikipedia? Wikipedia is the best thing ever. Anyone in the world can writeanything they want about any subject, so you know you re getting the best possible information. – Steve Carell, The Office 25
What would make you trust Wikipedia more? Nothing 26
What would make you trust Wikipedia more? Wikipedia, just by its nature, is impossible to trust completely. I dont think this can necessarily be changed. 27
WikiDashboard Transparency of social dynamics can reduce conflict and coordination issues Attribution encourages contribution – WikiDashboard: Social dashboard for wikis – Prototype system: http://wikidashboard.parc.com Visualization for every wiki page showing edit history timeline and top individual editors Can drill down into activity history for specific editors and view edits to see changes side-by-sideCitation: Suh et al.CHI 2008 Proceedings Crowdsourcing Meetup (Stanford 28
Hillary Clinton Crowdsourcing Meetup (Stanford 292011) 29
Top Editor -‐ Wasted Time R Crowdsourcing Meetup (Stanford 30 2011)
Surfacing information• Numerous studies mining Wikipedia revision history to surface trust-relevant information – Adler & Alfaro, 2007; Dondio et al., 2006; Kittur et al., 2007; Viegas et al., 2004; Zeng et al., 2006 Suh, Chi, Kittur, & Pendleton, CHI2008• But how much impact can this have on user perceptions in a system which is inherently mutable? 31
Hypotheses1. Visualization will impact perceptions of trust2. Compared to baseline, visualization will impact trust both positively and negatively3. Visualization should have most impact when high uncertainty about article • Low quality • High controversy 32
Design • 3 x 2 x 2 design Controversial UncontroversialVisualization Abortion Volcano High quality• High stability George Bush Shark• Low stability• Baseline (none) Pro-life feminism Disk defragmenter Low quality Scientology and celebrities Beeswax 33
Method• Users recruited via Amazon s Mechanical Turk – 253 participants – 673 ratings – 7 cents per rating – Kittur, Chi, & Suh, CHI 2008: Crowdsourcing user studies• To ensure salience and valid answers, participants answered: – In what time period was this article the least stable? – How stable has this article been for the last month? – Who was the last editor? – How trustworthy do you consider the above editor? 40
Results 7 High stability Baseline Low stability 6 Trustworthiness rating 5 4 3 2 1 Low qual High qual Low qual High qual Uncontroversial Controversialmain effects of quality and controversy:• high-quality articles > low-quality articles (F(1, 425) = 25.37, p < .001)• uncontroversial articles > controversial articles (F(1, 425) = 4.69, p = .031) 41
Results 7 High stability Baseline Low stability 6 Trustworthiness rating 5 4 3 2 1 Low qual High qual Low qual High qual Uncontroversial Controversialinteraction effects of quality and controversy:• high quality articles were rated equally trustworthy whether controversialor not, while• low quality articles were rated lower when they were controversial thanwhen they were uncontroversial. 42
Results1. Significant effect of 7 High stability Baseline Low stability visualization 6 Trustworthiness rating – High > low, p < .001 52. Viz has both positive and 4 negative effects 3 – High > baseline, p < .001 2 – Low > baseline, p < .01 1 Low qual High qual Low qual High qual3. No interaction of Uncontroversial Controversial visualization with either quality or controversy – Robust across conditions 43
Results1. Significant effect of 7 High stability Baseline Low stability visualization 6 Trustworthiness rating – High > low, p < .001 52. Viz has both positive and 4 negative effects 3 – High > baseline, p < .001 2 – Low > baseline, p < .01 1 Low qual High qual Low qual High qual3. No interaction of Uncontroversial Controversial visualization with either quality or controversy – Robust across conditions 44
Results1. Significant effect of 7 High stability Baseline Low stability visualization 6 Trustworthiness rating – High > low, p < .001 52. Viz has both positive and 4 negative effects 3 – High > baseline, p < .001 2 – Low > baseline, p < .01 1 Low qual High qual Low qual High qual3. No interaction effect of Uncontroversial Controversial visualization with either quality or controversy – Robust across conditions 45