Recognition: no theorem link
On the Limits of PAC Learning of Networks from Opinion Dynamics
Pith reviewed 2026-05-15 03:05 UTC · model grok-4.3
The pith
Networks with unanimity-style opinion updates can be learned efficiently from samples via PAC algorithms when each agent has a bounded number of influencers, but majority updates make efficient learning impossible under standard complexity.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
If the opinion dynamics follow a threshold rule in which a fixed number of influencers prevent opinion change (for example unanimity and quasi-unanimity), there exists an efficient PAC learning algorithm provided the number of influencers per agent is bounded; if instead agents follow the majority of their influencers, then no efficient PAC learning algorithm exists under standard computational complexity assumptions.
What carries the argument
PAC learning of the directed influence graph from samples of synchronous deterministic threshold opinion updates, with bounded in-degree for the positive case.
If this is right
- The influence graph can be recovered exactly with high probability using polynomially many samples when the threshold prevents change unless all or nearly all influencers agree and in-degree is bounded.
- Majority dynamics render network recovery computationally intractable in the PAC sense.
- A simple polynomial-time heuristic recovers consistent networks in over 98 percent of simulations on random graphs and never fails under certain conditions on agent count and sample size.
- Learning succeeds precisely when the observed updates are generated by the exact synchronous deterministic rule with no external noise.
Where Pith is reading between the lines
- The result implies that social-media platforms might deliberately favor high-threshold rules if they wish to make hidden influence structures harder to infer from public activity logs.
- Empirical tests on real opinion-trace datasets could check whether observed dynamics are closer to the learnable unanimity regime or the hard majority regime.
- Extending the positive algorithm to tolerate small amounts of asynchronous updates or observation noise would be a direct next step that preserves the bounded-influencer premise.
- The hardness proof for majority suggests that similar intractability may hold for other low-threshold rules, opening a classification of which threshold values permit efficient network learning.
Load-bearing premise
Opinion updates follow exactly a deterministic threshold rule with a fixed number of influencers per agent (or exactly majority), and samples are drawn from the synchronous update process without noise or hidden variables.
What would settle it
A concrete polynomial-time algorithm that PAC-learns the network under majority dynamics from update samples, or a family of graphs where the proposed heuristic fails to return a consistent network with non-negligible probability.
read the original abstract
Agents in social networks with threshold-based dynamics change opinions when influenced by sufficiently many peers. Existing literature typically assumes that the network structure and dynamics are fully known, which is often unrealistic. In this work, we ask how to learn a network structure from samples of the agents' synchronous opinion updates. Firstly, if the opinion dynamics follow a threshold rule in which a fixed number of influencers prevent opinion change (e.g., unanimity and quasi-unanimity), we provide an efficient PAC learning algorithm provided that the number of influencers per agent is bounded. Secondly, under standard computational complexity assumptions, we prove that if agents' opinions follow the majority of their influencers, then there is no efficient PAC learning algorithm. We propose a polynomial-time heuristic that successfully learns consistent networks in over $98\%$ of our simulations on random graphs, with no failures for some specified conditions on the numbers of agents and opinion diffusion examples.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies PAC learnability of network structures from samples of synchronous opinion updates under deterministic threshold dynamics. It gives a constructive efficient algorithm for high-threshold rules (unanimity and quasi-unanimity) when each agent has a bounded number of influencers, proves that no efficient PAC algorithm exists for majority dynamics under standard complexity assumptions, and presents a polynomial-time heuristic whose empirical success rate exceeds 98% on random graphs with no failures under certain parameter regimes.
Significance. If the algorithmic and hardness results hold, the work sharply delineates the boundary between efficiently learnable and intractable opinion-dynamics models, supplying both a positive constructive algorithm that exploits restrictive update conditions and a hardness reduction that relies on external complexity assumptions rather than internal circularity. The heuristic's simulation performance on random graphs provides practical evidence of utility even though it lacks worst-case guarantees.
major comments (2)
- [Algorithm description (following the abstract claim)] The positive PAC result for bounded-influencer high-threshold rules is load-bearing for the central claim yet the manuscript provides no explicit sample-complexity bound in terms of the influencer bound k, number of agents n, and failure probability; the efficiency statement therefore remains qualitative rather than quantitative.
- [Heuristic and simulation section] The heuristic is presented as polynomial-time and empirically successful in >98% of trials, but the manuscript contains no analysis of its approximation ratio, failure probability, or the precise conditions on n and number of diffusion examples that guarantee zero failures; this gap directly affects the practical contribution.
minor comments (2)
- [Preliminaries] Notation for the threshold parameter and the influencer set should be introduced once and used consistently; occasional reuse of symbols for different quantities reduces readability.
- [Experimental evaluation] The simulation setup (graph model, number of trials, exact parameter ranges for the 'no failures' regime) should be stated in a single table or paragraph rather than scattered across the text.
Simulated Author's Rebuttal
We thank the referee for the positive recommendation of minor revision and for the constructive comments that help clarify the presentation of our results. We address each major comment below.
read point-by-point responses
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Referee: [Algorithm description (following the abstract claim)] The positive PAC result for bounded-influencer high-threshold rules is load-bearing for the central claim yet the manuscript provides no explicit sample-complexity bound in terms of the influencer bound k, number of agents n, and failure probability; the efficiency statement therefore remains qualitative rather than quantitative.
Authors: We appreciate the referee highlighting this point. Our algorithm is fully constructive: for each agent it enumerates all possible influencer sets of size at most k and retains only those consistent with the observed synchronous updates. This immediately yields a polynomial-time procedure once k is treated as a fixed constant. While the manuscript states that the procedure is efficient, we acknowledge that an explicit sample-complexity expression (in terms of k, n, ε, and δ) was not written out. In the revision we will add the derivation: a standard Hoeffding-plus-union-bound argument over the O(n · binom(n,k)) candidate hypotheses produces an explicit PAC sample bound that is polynomial in n and 1/ε for any fixed k. This makes the efficiency claim quantitative without altering the algorithm itself. revision: yes
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Referee: [Heuristic and simulation section] The heuristic is presented as polynomial-time and empirically successful in >98% of trials, but the manuscript contains no analysis of its approximation ratio, failure probability, or the precise conditions on n and number of diffusion examples that guarantee zero failures; this gap directly affects the practical contribution.
Authors: We agree that the heuristic is presented purely as a practical polynomial-time method without worst-case guarantees. It is a simple greedy procedure that iteratively adds the smallest set of edges consistent with observed opinion flips; no approximation ratio or high-probability failure bound is claimed or proved. In the revised manuscript we will explicitly state these limitations and supply the exact simulation parameters (graph size n, number of diffusion traces m, and threshold values) under which zero failures were observed. We believe the >98 % empirical success rate on random graphs still provides useful practical evidence, but we will clarify that the contribution is empirical rather than theoretical. revision: yes
Circularity Check
No significant circularity detected
full rationale
The paper's positive PAC result follows from an explicit constructive algorithm that recovers bounded-influence neighbor sets by exploiting the restrictive threshold update rules (unanimity/quasi-unanimity) on observed synchronous flips; the negative result for majority dynamics is a standard complexity reduction under external assumptions. No derivation step reduces by construction to a fitted parameter, self-definition, or load-bearing self-citation chain. The model assumptions (deterministic synchronous updates, no noise) are stated upfront and the heuristic is presented only as an empirical supplement, not as a theoretical claim. The derivation is therefore self-contained.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Opinion updates follow a deterministic threshold rule with a fixed number of influencers per agent
- domain assumption Standard computational complexity assumptions (e.g., P ≠ NP or similar)
Reference graph
Works this paper leans on
-
[1]
Jour- nal of Economic Theory106(2), 265–295 (2002) https://doi.org/10.1006/jeth
Jackson, M.O., Watts, A.: The Evolution of Social and Economic Networks. Jour- nal of Economic Theory106(2), 265–295 (2002) https://doi.org/10.1006/jeth. 2001.2903
-
[3]
Election Manipulation on Social Networks with Messages on Multiple Candidates
Castiglioni, M., Ferraioli, D., Landriani, G., Gatti, N.: Election Manipulation on Social Networks with Messages on Multiple Candidates. CoRRabs/1902.03779 (2019). arXiv: 1902.03779
work page internal anchor Pith review Pith/arXiv arXiv 1902
-
[4]
Leskovec, J., Krause, A., Guestrin, C., Faloutsos, C., VanBriesen, J., Glance, N.: Cost-Effective Outbreak Detection in Networks. In: Proceedings of the 13th ACM SIGKDD International Conference on Knowledge Discovery And Data Mining. KDD ’07, pp. 420–429. Association for Computing Machinery, New York, NY, USA (2007). https://doi.org/10.1145/1281192.128123...
-
[5]
In: Proceedings of the 2023 International Conference on Autonomous Agents and Multiagent Systems
Deligkas, A., Eiben, E., Goldsmith, T.-L., Skretas, G.: Being an Influencer is Hard: The Complexity of Influence Maximization in Temporal Graphs with a Fixed Source. In: Proceedings of the 2023 International Conference on Autonomous Agents and Multiagent Systems. AAMAS ’23, pp. 2222–2230. International Foun- dation for Autonomous Agents and Multiagent Sys...
work page 2023
-
[6]
Theoretical Population Biology88, 68–77 (2013) https://doi.org/10.1016/j.tpb.2013.06.006
Fogarty, L., Creanza, N., Feldman, M.W.: The role of cultural transmission in human demographic change: An age-structured model. Theoretical Population Biology88, 68–77 (2013) https://doi.org/10.1016/j.tpb.2013.06.006
-
[7]
Journal of The Royal Society Interface20(2023) https://doi.org/10.1098/rsif.2022.0736
Galesic, M., Barkoczi, D., Berdahl, A.M., Biro, D., Carbone, G., Giannoccaro, I., Goldstone, R.L., Gonzalez, C., Kandler, A., Kao, A.B., Kendal, R., Kline, M., Lee, E., Massari, G.F., Mesoudi, A., Olsson, H., Pescetelli, N., Sloman, S.J., Smaldino, P.E., Stein, D.L.: Beyond collective intelligence: Collective adaptation. Journal of The Royal Society Inter...
-
[8]
Reconstructing Waddington’s landscape from data
Ammar, M., Fogarty, L., Kandler, A.: Social learning and memory. Proceedings of the National Academy of Sciences120(33) (2023) https://doi.org/10.1073/pnas. 2310033120 . Publisher: Proceedings of the National Academy of Sciences
-
[9]
Nature communications 5, 3526 (2014) https://doi.org/10.1038/ncomms4526
Gavrilets, S., Fortunato, L.: A Solution to the Collective Action Problem in Between-Group Conflict and Within-Group Inequality. Nature communications 5, 3526 (2014) https://doi.org/10.1038/ncomms4526
-
[10]
Chistikov, D., Lisowski, G., Paterson, M., Turrini, P.: Convergence of Opinion 26 Diffusion is PSPACE-Complete. Proceedings of the AAAI Conference on Artificial Intelligence34(05), 7103–7110 (2020) https://doi.org/10.1609/aaai.v34i05.6197
-
[11]
Journal of Statistical Physics181(2020) https: //doi.org/10.1007/s10955-020-02625-w
Mukhopadhyay, A., Mazumdar, R., Roy, R.: Voter and Majority Dynamics with Biased and Stubborn Agents. Journal of Statistical Physics181(2020) https: //doi.org/10.1007/s10955-020-02625-w
-
[12]
In: Markakis, E., Sch¨ afer, G
Auletta, V., Caragiannis, I., Ferraioli, D., Galdi, C., Persiano, G.: Minority Becomes Majority in Social Networks. In: Markakis, E., Sch¨ afer, G. (eds.) Web and Internet Economics, pp. 74–88. Springer, Berlin, Heidelberg (2015)
work page 2015
-
[13]
Kempe, D., Kleinberg, J., Tardos, E.: Maximizing the Spread of Influence through a Social Network. In: Proceedings of the Ninth ACM SIGKDD Inter- national Conference on Knowledge Discovery And Data Mining. KDD ’03, pp. 137–146. Association for Computing Machinery, New York, NY, USA (2003). https://doi.org/10.1145/956750.956769 . event-place: Washington, D...
-
[14]
Bredereck, R., Elkind, E.: Manipulating Opinion Diffusion in Social Networks. In: Proceedings of the Twenty-Sixth International Joint Conference on Artificial Intelligence, IJCAI-17, pp. 894–900 (2017). https://doi.org/10.24963/ijcai.2017/ 124 .https://doi.org/10.24963/ijcai.2017/124
-
[15]
Government Information Quarterly 39(3), 101709 (2022) https://doi.org/10.1016/j.giq.2022.101709
Kushwaha, A.K., Kar, A.K., Roy, S.K., Ilavarasan, P.V.: Capricious opinions: A study of polarization of social media groups. Government Information Quarterly 39(3), 101709 (2022) https://doi.org/10.1016/j.giq.2022.101709
-
[16]
Netrapalli, P., Sanghavi, S.: Learning the Graph of Epidemic Cascades. In: Pro- ceedings of the 12th ACM SIGMETRICS/PERFORMANCE Joint International Conference on Measurement and Modeling Of Computer Systems. SIGMET- RICS ’12, pp. 211–222. Association for Computing Machinery, New York, NY, USA (2012). https://doi.org/10.1145/2254756.2254783 . event-place: ...
-
[17]
Wilder, B., Immorlica, N., Rice, E., Tambe, M.: Maximizing Influence in an Unknown Social Network. Proceedings of the AAAI Conference on Artificial Intelligence32(1) (2018) https://doi.org/10.1609/aaai.v32i1.11585
-
[18]
IEEE Control Systems Magazine41(5), 61–103 (2021) https://doi.org/10.1109/MCS.2021.3092810
Ravazzi, C., Dabbene, F., Lagoa, C., Proskurnikov, A.V.: Learning Hidden Influ- ences in Large-Scale Dynamical Social Networks: A Data-Driven Sparsity-Based Approach, in Memory of Roberto Tempo. IEEE Control Systems Magazine41(5), 61–103 (2021) https://doi.org/10.1109/MCS.2021.3092810
-
[19]
In: Proceedings of the 23rd International Conference on Autonomous Agents and Multiagent Systems
Chistikov, D., Estrada, L., Paterson, M., Turrini, P.: Learning a Social Network by Influencing Opinions. In: Proceedings of the 23rd International Conference on Autonomous Agents and Multiagent Systems. AAMAS ’24, pp. 363–371. Inter- national Foundation for Autonomous Agents and Multiagent Systems, Richland, 27 SC (2024). event-place: Auckland, New Zealand
work page 2024
-
[20]
Artificial Intelligence284, 103288 (2020) https://doi.org/10.1016/j.artint.2020.103288
Auletta, V., Ferraioli, D., Greco, G.: On the complexity of reasoning about opin- ion diffusion under majority dynamics. Artificial Intelligence284, 103288 (2020) https://doi.org/10.1016/j.artint.2020.103288
-
[21]
In: NIPS (2010).https://api.semanticscholar.org/CorpusID:6812407
Myers, S.A., Leskovec, J.: On the Convexity of Latent Social Network Inference. In: NIPS (2010).https://api.semanticscholar.org/CorpusID:6812407
work page 2010
-
[22]
Gomez-Rodriguez, M., Balduzzi, D., Scholkopf, B.: Uncovering the Temporal Dynamics of Diffusion Networks. In: Proceedings of the 28th International Con- ference on International Conference on Machine Learning. ICML’11, pp. 561–568. Omnipress, Madison, WI, USA (2011). event-place: Bellevue, Washington, USA
work page 2011
-
[23]
Games11(4) (2020) https://doi.org/10.3390/g11040065
Grabisch, M., Rusinowska, A.: A Survey on Nonstrategic Models of Opinion Dynamics. Games11(4) (2020) https://doi.org/10.3390/g11040065
-
[24]
Baldassarri, S., Gallo, A., Jacquier, V., Zocca, A.: Ising model on clustered net- works: A model for opinion dynamics. Physica A: Statistical Mechanics and its Applications623, 128811 (2023) https://doi.org/10.1016/j.physa.2023.128811
-
[25]
Liggett, T.M.: Interacting Particle Systems. Classics in Mathematics. Springer, ??? (2004).https://books.google.co.uk/books?id=I3aNPR1FursC
work page 2004
-
[26]
In: Caires, L., Italiano, G.F., Monteiro, L., Palamidessi, C., Yung, M
Kempe, D., Kleinberg, J.M., Tardos, E.: Influential Nodes in a Diffusion Model for Social Networks. In: Caires, L., Italiano, G.F., Monteiro, L., Palamidessi, C., Yung, M. (eds.) Automata, Languages and Programming, 32nd International Colloquium, ICALP 2005, Lisbon, Portugal, July 11-15, 2005, Proceedings. Lec- ture Notes in Computer Science, vol. 3580, p...
-
[27]
Chen, W., Wang, Y., Yang, S.: Efficient Influence Maximization in Social Networks. In: Proceedings of the 15th ACM SIGKDD Interna- tional Conference on Knowledge Discovery And Data Mining. KDD ’09, pp. 199–208. Association for Computing Machinery, New York, NY, USA (2009). https://doi.org/10.1145/1557019.1557047 . event-place: Paris, France. https://doi.o...
-
[28]
In: Proceedings of the 2015 ACM SIGMOD Inter- national Conference on Management of Data
Tang, Y., Shi, Y., Xiao, X.: Influence Maximization in Near-Linear Time: A Martingale Approach. In: Proceedings of the 2015 ACM SIGMOD Inter- national Conference on Management of Data. SIGMOD ’15, pp. 1539–1554. Association for Computing Machinery, New York, NY, USA (2015). https:// doi.org/10.1145/2723372.2723734 . event-place: Melbourne, Victoria, Austr...
-
[29]
Narasimhan, H., Parkes, D.C., Singer, Y.: Learnability of influence in networks. 28 In: Proceedings of the 29th International Conference on Neural Information Pro- cessing Systems - Volume 2. NIPS’15, pp. 3186–3194. MIT Press, Cambridge, MA, USA (2015). event-place: Montreal, Canada
work page 2015
-
[30]
Gomez-Rodriguez, M., Leskovec, J., Krause, A.: Inferring networks of diffusion and influence. Proceedings of the 16th ACM SIGKDD international conference on Knowledge discovery and data mining (2010)
work page 2010
-
[31]
Qiu, Z., Adiga, A., Marathe, M.V., Ravi, S.S., Rosenkrantz, D.J., Stearns, R.E., Vullikanti, A.: Learning the topology and behavior of discrete dynamical systems. In: Proceedings of the Thirty-Eighth AAAI Conference on Artificial Intelligence and Thirty-Sixth Conference on Innovative Applications of Artificial Intelligence and Fourteenth Symposium on Educ...
-
[32]
MIT Press, Cambridge, MA, USA (1994)
Kearns, M.J., Vazirani, U.V.: An Introduction to Computational Learning Theory. MIT Press, Cambridge, MA, USA (1994)
work page 1994
-
[33]
Journal of Machine Learning Research17(38), 1–15 (2016)
Hanneke, S.: The Optimal Sample Complexity of PAC Learning. Journal of Machine Learning Research17(38), 1–15 (2016)
work page 2016
-
[34]
Blumer, A., Ehrenfeucht, A., Haussler, D., Warmuth, M.K.: Learnability and the Vapnik-Chervonenkis dimension. J. ACM36, 929–965 (1989)
work page 1989
-
[35]
Information and Computation 82(3), 247–261 (1989) https://doi.org/10.1016/0890-5401(89)90002-3
Ehrenfeucht, A., Haussler, D., Kearns, M., Valiant, L.: A general lower bound on the number of examples needed for learning. Information and Computation 82(3), 247–261 (1989) https://doi.org/10.1016/0890-5401(89)90002-3
-
[36]
Cambridge University Press, USA (1992)
Anthony, M., Biggs, N.: Computational Learning Theory: an Introduction. Cambridge University Press, USA (1992)
work page 1992
-
[37]
McGraw- Hill, Inc., USA (2006)
Dasgupta, S., Papadimitriou, C.H., Vazirani, U.: Algorithms, 1st edn. McGraw- Hill, Inc., USA (2006)
work page 2006
-
[38]
Theoretical Computer Science Stack Exchange (2017)
Rudoy, M.: NP-hardness of finding 0-1 vector to maximize rows of -1, +1 matrix. Theoretical Computer Science Stack Exchange (2017). https://cstheory. stackexchange.com/q/39786
work page 2017
-
[39]
Discrete Math- ematics13(4), 383–390 (1975) https://doi.org/10.1016/0012-365X(75)90058-8
Lov´ asz, L.: On the ratio of optimal integral and fractional covers. Discrete Math- ematics13(4), 383–390 (1975) https://doi.org/10.1016/0012-365X(75)90058-8
-
[40]
Feige, U.: A threshold of ln n for approximating set cover. J. ACM45(4), 634– 652 (1998) https://doi.org/10.1145/285055.285059 . Place: New York, NY, USA Publisher: Association for Computing Machinery 29
-
[41]
Arpino, G., Dmitriev, D., Grometto, N.: Greedy Heuristics and Linear Relax- ations for the Random Hitting Set Problem. eprint: 2305.05565 (2023). https: //arxiv.org/abs/2305.05565 30
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