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Altruistic E conomics

www.altruists.org. Introduction to Imaginary Friends. Altruistic E conomics. A E 1 8 : The Imaginary Friends Test. v1.0. A presentation by Dr. Robin Upton (2006-01-28) Available for download at www.altruists.org/ae14

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Altruistic E conomics

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  1. www.altruists.org Introduction to Imaginary Friends Altruistic Economics AE18: The Imaginary Friends Test v1.0 A presentation by Dr. Robin Upton (2006-01-28) Available for download atwww.altruists.org/ae14 Attribution – NonCommercial - ShareAlike Recommended Pre-requisite: AE10: Keeping Score

  2.     Real Individual User Artificial Construct . F2F Network Growth Introduction to Imaginary Friends • Altruistic Economicsis a decentralised system, so users have a lot of autonomy... . , such as the chance to create Imaginary Friends: • Rewarding such Imaginary Friendswould encourage deception.

  3.      Sybil Attacks F2F Network Growth TheFriend2Friend network grows organically, over real social relationships. Each new member creates an online server and is linked in by friends.  The idea is, everyone has one online server. However,like WWW, there is no centre, noone in charge, no list of members.

  4.          The ‘Imaginary Friends’ Test Sybil Attacks ‘Sybil’ was the first person diagnosed with so-called ‘Multiple Personality Disorder’.   A Sybil Attack is an attempt todefraud an online system by using fake identities.

  5. FAIL: Incentive to Cheat 3. Imaginary Friends are an advantage:        PASS:  No Incentive to Cheat          1. Imaginary Friends make no difference:  2. Imaginary Friends are a disadvantage:  . Media Sharing The ‘Imaginary Friends’ Test “Does it help to create ‘imaginary friends’?”

  6. Aysha I value your opinion… Birbal I value your opinion… “Chinese Whispers” I know this film Chris Basic Framework Media Sharing MEDIA SHARING is a project to network people who review files and then benefit from one another’s opinions. Aysha wants an opinion about the film ‘Chinese Whispers’… How to quantify this process... ?

  7. Aysha I value your opinion… 0.3 I value your opinion… 0.4 I rate this file… 0.8 Birbal “Chinese Whispers” Chris SoAysha has one recommendation: Value=0.12 Rating=0.8 Combining Recommendations Basic Framework Assume: • Individuals make 2 sorts of evaluations: 1) ‘I value your opinion’ is quantified as V: 0<=V<=1 2) ‘I rate this File’is quantified as R: 0<=R<=1 • Individuals who don’t rate a file defer to their friends • Friends of friends’ opinions are valued multiplicatively

  8. So, if Aysha has 4 recommendations: Value=0.15 Rating=0.6 Value=0.8 Rating=0.5 Value=0.08 Rating=0.6 Value=0.12 Rating=0.8 0.15×0.6+ 0.8×0.5+ 0.08×0.6+ 0.12×0.8 0.15+0.8+0.08+0.12 Note the high value of the 2nd rating, which means it dominates the others. Applying The Test Combining Recommendations Ratings are averaged according to value, to give a single figure. Weighted average = ≈ 0.55

  9. … Value=VB Rating = R Value=VB Rating=R Value=VB Rating=R I value your opinion… 1.0 I value your opinion… 1.0 I value your opinion… 1.0 Rating = R MBogo1 MBogo2 MBogoN … Rating = R “Chinese Whispers” { N separate ratings have Overall value = NVB Chris A Problem Applying The Test What if Chris made Imaginary Friends to rate the file for him?

  10. Value=0.15 Rating=0.6 Value=NVB Rating=R Value=0.8 Rating=0.5 Value=0.08 Rating=0.6 If Nis big enough, no one else’s ratings count! Imaginary friends can increase an individuals’ impact, so the algorithm fails the imaginary friends test. A Modification A Problem So, if Aysha has 4 recommendations: Chris could use his Imaginary Friends to dominate the other ratings.

  11. Value=VB V1 Rating = R v2 … vN Rating = R MBogoN MBogo2 MBogo1 … Nfriends give Chris N ratings, with a value of ∑Vf. Rating = R “Chinese Whispers” f Let’s require ∑Vf=1 Chris f Summary of The ‘Imaginary Friends’ Test A Modification To control the imaginary friends, we add a constraintto the model.

  12. Chris …} N such friends Vf MBogof Rating = R Rating =Rf VB VB “Chinese Whispers” Overall rating: Value= VB∑VfRating=∑VfRf “Chinese Whispers” Since ∑Vf=1,1≥R,Rf≥0… f f f Chris So the modified algorithm passes the imaginary friends test. Modified Algorithm Examined Modified Algorithm Examined With N>0 imaginary friends: As an individual: Single rating: Value=VBRating=R imaginary friends confer no advantage.

  13. Creating Imaginary Friends should not confer any advantage:      Recommended Further Reading: AE19: Preventing Abuse http://www.altruists.org/ae19 Summary of The Imaginary Friends Test • Sybil Attacksare a feature of decentralised systems. • Applying the Imaginary Friends Test helps deduce algorithms suitable for decentralised systems.

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