Introduction to Bayesian Inference for Psychology

We introduce the fundamental tenets of Bayesian inference, which derive from two basic laws of probability theory. We cover the interpretation of probabilities, discrete and continuous versions of Bayes’ rule, parameter estimation, and model comparison. Using seven worked examples, we illustrate these principles and set up some of the technical background for the rest of this special issue of Psychonomic Bulletin & Review. Supplemental material is available via https://osf.io/wskex/.     

An Inconsistency in the Philebus?

Plato's Philebus contains an intricate difficulty. Plato seems to hold both (a) that all pleasures are processes of becoming, a crucial premise in the argument that no pleasure is good (53c–55c) and (b) that some pleasures contribute in their own right to the goodness of the best life (64c–67b). Since it seems also plausible that only things which are good can contribute to the goodness of the best life in their own right, Plato's view seems to be inconsistent. Interpreters usually reject either (a) or (b). As Plato seems firmly committed to both (a) and (b), I propose a third way of dealing with the inconsistency. The apparent inconsistency highlights a vital contrast between what is independently good (good per se), what is dependently good (good through participating in what is independently good), and what is derivatively good (good through standing in a certain relation to dependent goods). I argue that while pleasure's being a process of becoming marks it out as derivatively good, some kinds of pleasure are also dependent goods in virtue of their objects – irrespective of their being processes of becoming.     

Perfectionism and social desirability: Students report increased perfectionism to create a positive impression

Because previous studies examining correlations between perfectionism and social desirability produced inconclusive findings, this study used an experimental approach examining the perceived social desirability of perfectionism. 117 university students were randomly assigned to three conditions (fake-good, standard, and fake-bad instructions) and then completed measures of self-oriented, other-oriented, and socially prescribed perfectionism. Results showed that all three forms of perfectionism were perceived as socially desirable. Self-oriented perfectionism showed a strong linear trend across the conditions: Students reported significantly higher self-oriented perfectionism in the fake-good condition, and significantly lower self-oriented perfectionism in the fake-bad condition compared to standard instructions. Other-oriented perfectionism showed the same linear trend, albeit weaker, and only fake-good and fake-bad conditions differed significantly. Socially prescribed perfectionism too showed a significant linear trend: Students reported higher levels in the fake-good condition compared to standard instructions and fake-bad condition, with no significant difference between the latter conditions. The findings indicate that, in educational settings, students perceive perfectionism—including maladaptive forms such as socially prescribed perfectionism—as socially desirable.     

Comparisons in research and reasoning: Toward an integrative theory of social induction

Strong scientific theories give coherence to a body of research findings, make precise predictions about key phenomena, and guide the search for new discoveries. In social psychology, some contemporary theories fall short of this ideal. Mini-theories are prevalent (cf. Van Lange, Higgins, & Kruglanski, 2011), many predictions are merely directional (like this one!) and theorizing post-hoc. Guided by experimental reasoning, many researchers emphasize—and reify—empirical differences. Taking the experimental method as an epistemological gold standard, they regard comparative thinking as a criterion of rational thinking. Using examples from social judgment and decision making, we show how comparative reasoning can constrain theoretical development and bias assessments of human rationality. To encourage movement toward stronger theory, we describe a model of inductive reasoning in social contexts.     

When the whole is more than the sum of its parts: Group motivation gains in the wild

Whereas negative effects of groups on individual motivation have been reported for many years, recent research has begun to show when and why working in a group can produce motivation gains compared to individual work. So far, this evidence has been limited to laboratory settings and rather simple tasks. Using data from swimming competitions at the 2008 Olympics, evidence is presented that motivation gains in groups also occur in field settings with more complex tasks. Based on an instrumentality × value approach, we expect that late positions in a relay trigger motivation gains in groups due to an increase in perceived indispensability for the group outcome. This idea has been initially tested in a pilot study with competitive swimmers, demonstrating that perceived indispensability for the relay outcome indeed increases with later serial positions in a relay. Moreover, the main study with data from the 2008 Olympics revealed performance times consistent with this pattern of indispensability perceptions: while starting swimmers in the swimming relays performed at similar levels as in their individual competitions, swimmers at the later positions showed higher performance in the relay compared to their individual competition heats.     

Impact of instruction on the acquisition of sequence knowledge in a sensorimotor task

We examined whether and to what extent a sequence of finger movements can be learned and transferred to the untrained hand according to the muscle homology depending on the relative salience of response locations and effectors. Participants performed a discrete sequence production task, in which they were asked to learn a sequence of either key locations or of finger movements. Each training block was followed by a transfer block in which responding with the opposite hand was required. Before the last transfer block participants received an unexpected instruction. They had to reproduce the sequence of key locations instead of the sequence of finger movements and conversely, the sequence of finger movements instead of the sequence of key locations. The results do not support the existence of a sequence representation for the order of finger movements irrespective of the hand used.     

A hierarchical latent stochastic differential equation model for affective dynamics

In this article a continuous-time stochastic model (the Ornstein-Uhlenbeck process) is presented to model the perpetually altering states of the core affect, which is a 2-dimensional concept underlying all our affective experiences. The process model that we propose can account for the temporal changes in core affect on the latent level. The key parameters of the model are the average position (also called home base), the variances and covariances of the process, and the regulatory mechanisms that keep the process in the vicinity of the average position. To account for individual differences, the model is extended hierarchically. A particularly novel contribution is that in principle all parameters of the stochastic process (not only the mean but also its variance and the regulatory parameters) are allowed to differ between individuals. In this way, the aim is to understand the affective dynamics of single individuals and at the same time investigate how these individuals differ from one another. The final model is a continuous-time state-space model for repeated measurement data taken at possibly irregular time points. Both time-invariant and time-varying covariates can be included to investigate sources of individual differences. As an illustration, the model is applied to a diary study measuring core affect repeatedly for several individuals (thereby generating intensive longitudinal data).