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Johansson, Tobias

Kristianstad University, School of Education and Environment, Avdelningen för Psykologi.

Generating artificial social networks2019In: The Quantitative Methods for Psychology, ISSN 1017-3455, E-ISSN 1543-8740, Vol. 15, no 2, p. 56-74Article in journal (Refereed)

Abstract [en]

The study of complex social networks is an inherently interdisciplinary research area with applications across many fields, including psychology. Social network models describe, illustrate and explain how people are connected to each other and can, for example, be used to study information spread and interconnectedness of people with different kinds of traits. One approach to social network modelling, originating mainly in the physics literature, is to generate targeted kinds of social networks using models with specialized mechanisms while analyzing and deriving features of the models. Surprisingly though, and despite the popularity of this approach, there is no available functionality for generating a wide variety of social networks from these models. Thus, researchers are left to implement and specify these models themselves, restricting the applicability of these models. In this article, I provide a set of Matlab functions enabling the generation of artificial social networks from 22 different network models, most of them explicitly designed to capture features of social networks. Many of these models originate in the physics literature and may therefore not be familiar to psychological researchers. I also provide an illustration of how these models can be evaluated in terms of a simulated model comparison approach and how they can be applied to psychological research. With the already existing network functionality available in Matlab and other languages, this should provide a useful extension to researchers.

Kristianstad University, School of Education and Environment, Avdelningen för Psykologi.

Gossip spread in social network models2017In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 417, no 1, p. 126-134Article in journal (Refereed)

Abstract [en]

Gossip almost inevitably arises in real social networks. In this article we investigate the relationship between the number of friends of a person and limits on how far gossip about that person can spread in the network. How far gossip travels in a network depends on two sets of factors: (a) factors determining gossip transmission from one person to the next and (b) factors determining network topology. For a simple model where gossip is spread among people who know the victim it is known that a standard scale-free network model produces a non-monotonic relationship between number of friends and expected relative spread of gossip, a pattern that is also observed in real networks (Lind et al., 2007). Here, we study gossip spread in two social network models (Toivonen et al., 2006; Vázquez, 2003) by exploring the parameter space of both models and fitting them to a real Facebook data set. Both models can produce the non-monotonic relationship of real networks more accurately than a standard scale-free model while also exhibiting more realistic variability in gossip spread. Of the two models, the one given in Vázquez (2003) best captures both the expected values and variability of gossip spread.

Significance testing based on p-values is standard in psychological research and teaching. Typically, research articles and textbooks present and use p as a measure of statistical evidence against the null hypothesis (the Fisherian interpretation), although using concepts and tools based on a completely different usage of p as a tool for controlling long-term decision errors (the Neyman-Pearson interpretation). There are four major problems with using p as a measure of evidence and these problems are often overlooked in the domain of psychology. First, p is uniformly distributed under the null hypothesis and can therefore never indicate evidence for the null. Second, p is conditioned solely on the null hypothesis and is therefore unsuited to quantify evidence, because evidence is always relative in the sense of being evidence for or against a hypothesis relative to another hypothesis. Third, p designates probability of obtaining evidence (given the null), rather than strength of evidence. Fourth, p depends on unobserved data and subjective intentions and therefore implies, given the evidential interpretation, that the evidential strength of observed data depends on things that did not happen and subjective intentions. In sum, using p in the Fisherian sense as a measure of statistical evidence is deeply problematic, both statistically and conceptually, while the Neyman-Pearson interpretation is not about evidence at all. In contrast, the likelihood ratio escapes the above problems and is recommended as a tool for psychologists to represent the statistical evidence conveyed by obtained data relative to two hypotheses.