Determining informative priors for cognitive models

The development of cognitive models involves the creative scientific formalization of assumptions, based on theory, observation, and other relevant information. In the Bayesian approach to implementing, testing, and using cognitive models, assumptions can influence both the likelihood function of the model, usually corresponding to assumptions about psychological processes, and the prior distribution over model parameters, usually corresponding to assumptions about the psychological variables that influence those processes. The specification of the prior is unique to the Bayesian context, but often raises concerns that lead to the use of vague or non-informative priors in cognitive modeling. Sometimes the concerns stem from philosophical objections, but more often practical difficulties with how priors should be determined are the stumbling block. We survey several sources of information that can help to specify priors for cognitive models, discuss some of the methods by which this information can be formalized in a prior distribution, and identify a number of benefits of including informative priors in cognitive modeling. Our discussion is based on three illustrative cognitive models, involving memory retention, categorization, and decision making.     

Time-varying decision boundaries: insights from optimality analysis

The most widely used account of decision-making proposes that people choose between alternatives by accumulating evidence in favor of each alternative until this evidence reaches a decision boundary. It is frequently assumed that this decision boundary stays constant during a decision, depending on the evidence collected but not on time. Recent experimental and theoretical work has challenged this assumption, showing that constant decision boundaries are, in some circumstances, sub-optimal. We introduce a theoretical model that facilitates identification of the optimal decision boundaries under a wide range of conditions. Time-varying optimal decision boundaries for our model are a result only of uncertainty over the difficulty of each trial and do not require decision deadlines or costs associated with collecting evidence, as assumed by previous authors. Furthermore, the shape of optimal decision boundaries depends on the difficulties of different decisions. When some trials are very difficult, optimal boundaries decrease with time, but for tasks that only include a mixture of easy and medium difficulty trials, the optimal boundaries increase or stay constant. We also show how this simple model can be extended to more complex decision-making tasks such as when people have unequal priors or when they can choose to opt out of decisions. The theoretical model presented here provides an important framework to understand how, why, and whether decision boundaries should change over time in experiments on decision-making.     

Holistic face representation is highly orientation-specific

It has long been argued that face processing requires disproportionate reliance on holistic processing (HP), relative to that required for nonface object recognition. Nevertheless, whether the holistic nature of face perception is achieved via a unique internal representation or by the employment of an automated attention mechanism is still debated. Previous studies had used the face inversion effect (FIE), a unique face-processing marker, or the face composite task, a gold standard paradigm measuring holistic processing, to examine the validity of these two different hypotheses, with some studies combining the two paradigms. However, the results of such studies remain inconclusive, particularly pertaining to the issue of the two proposed HP mechanisms—an internal representation as opposed to an automated attention mechanism. Here, using the complete composite paradigm design, we aimed to examine whether face rotation yields a nonlinear or a linear drop in HP, thus supporting an account that face processing is based either on an orientation-dependent internal representation or on automated attention. Our results reveal that even a relatively small perturbation in face orientation (30 deg away from upright) already causes a sharp decline in HP. These findings support the face internal representation hypothesis and the notion that the holistic processing of faces is highly orientation-specific.     

Surprising depth cue captures attention in visual search

A substantial amount of evidence indicates that surprising events capture attention. The present study was primarily intended to investigate whether expectancy discrepant depth information also is able to capture attention immediately and—more specifically—whether cues that are relatively closer or farther differentially modulate behavior. For this purpose, participants had to identify one of two target letters in a search display. Stimulus positions were initially cued by uninformative placeholders. After half of the trials, the cue at the target position was suddenly and unexpectedly (critical trial) displayed closer to or farther from the observer. In line with previous research, both depth cues captured attention on their very first appearance. Performance in the critical trial was superior to the error rates in the trials without depth cue and was even above the performance in subsequent trials that included depth cue. This effect was only observed when the cue preceded the target by 400 ms. Using a shorter cue-stimulus interval of 100 ms, only a delayed improvement was observed, which denotes a typical feature of surprise capture. Moreover, response times were faster in trials comprising a depth cue, and this was already true for the critical trial. Apart from that, no other marked differences between near and far depth cues were observed. Therefore, the present results emphasize that surprising depth information indeed captures attention. However, in contrast to other perceptual tasks, search performance was not considerably influenced by relative position in depth.     

In Defense of Penalizing (but not Punishing) Civil Disobedience

While many contemporary political philosophers agree that citizens of a legitimate state enjoy a moral right to civil disobedience, they differ over both the grounds of that right and its content. This essay defends the view that the moral right to civil disobedience derives from (or is a facet of) a general right to political participation, and the characterization of that right as precluding the state from punishing, but not from penalizing, those who exercise it. The argument proceeds by way of rebuttals to criticisms of both claims recently advanced by Kimberley Brownlee. While in some cases those criticisms fail on their merits, in other cases the responses offered here reveal that the dispute over the ground and content of a moral right to civil disobedience reflects deeper disagreements regarding two foundational issues: first, whether moral rights are best conceived of as defeasible evaluative principles or conclusive normative ones, and second, whether principles of justice should be theorized on the basis of full or partial compliance.     

Autonomy and the Moral Symmetry Principle: Reply to Frowe and Tooley

Helen Frowe has recently objected to Michael Tooley’s famous Moral Symmetry Principle, which is meant to show that in themselves killing and letting die are morally equivalent. I argue that her objection is not compelling but a more compelling objection is available. Specifically, Tooley’s rebuttal of a proposed counter-example to his Moral Symmetry Principle has two problematic implications. First, it undercuts the very principle itself. If we reject the proposed counter-example, then any instance of the Moral Symmetry Principle will actually demonstrate the moral in-equivalence of killing and letting die. Second, it commits us to the view, which Tooley wishes to avoid, that we are just as obligated to refrain from doing wrong as we are to prevent others from doing the same. I conclude with a brief discussion of a more general concern regarding Tooley’s basic strategy. My focus here is quite narrow. My claims, if plausible, only show that the Moral Symmetry Principle is unsound and thus cannot serve as a basis for the view that killing and letting die are morally equivalent.     

Two Concepts of Basic Equality

It has become somewhat a commonplace in recent political philosophy to remark that all plausible political theories must share at least one fundamental premise, ‘that all humans are one another's equals’. One single concept of ‘basic equality’, therefore, is cast as the common touchstone of all contemporary political thought. This paper argues that this claim is false. Virtually all do indeed say that all humans are ‘equals’ in some basic sense. However, this is not the same sense. There are not one but (at least) two concepts of basic equality, and they reflect not a grand unity within political philosophy but a deep and striking division. I call these concepts ‘Equal Worth’ and ‘Equal Authority’. The former means that each individual’s good is of equal moral worth. The latter means that no individual is under the natural authority of anyone else. Whilst these two predicates are not in themselves logically inconsistent, I demonstrate that they are inconsistent foundation stones for political theory. A theory that starts from Equal Worth will find it near impossible to justify Equal Authority. And a theory that starts from Equal Authority will find any fact about the true worth of things, including ourselves, irrelevant to justifying legitimate action. This helps us identify the origin of many of our deepest and seemingly intractable disagreements within political philosophy, and directs our attention to the need for a clear debate about the truth and/or relationship between the two concepts. In short, my call to arms can be summed up in the demand that political philosophers never again be allowed to claim ‘that all human beings are equals’ full stop. They must be clear in what dimension they claim that we are equals—Worth or Authority (or perhaps something else).     

The Choice Architect’s Trilemma

Critics have long dismissed paternalistic choice architecture as conceptually muddled at best and oxymoronic at worst. In this article, I argue that this criticism remains true despite recent replies to the contrary. Further, I suggest that a similar conceptual criticism also applies to non-paternalistic choice architecture. This is due to a three-way tension between the effectiveness, avoidability, and distinctiveness of each nudge. To illustrate this tension, I provide a novel explanation of the mechanics of nudging and a taxonomy of these interventions. I then argue that choice architects who defend the distinctiveness of nudging according to how it guides our behaviour via our unreflective intuitive reasoning encounter a trilemma because the distinctiveness of nudging hinges on interventions being both avoidable and effective. Choice architects cannot achieve this aim without harnessing both our automatic and reflective systems of thought in tandem. However, this diminishes the distinctive character of nudging by bringing it closer to other traditional policy interventions. This establishes the choice architect’s trilemma: a nudge is likely to be either ineffective, effective via some morally unacceptable means, or effective in a manner that is conceptually indistinct from other evidence-based policy interventions.     

Risky prospects and risk aversion tendencies: does competition in the classroom depend on grading practices and knowledge of peer-status?

When students are faced with the decision of whether to assist a peer, they should be sensitive to the potential risks associated with doing so. Two factors associated with risky helping behaviour in the classroom are: (1) the grading practices that are used, and (2) knowledge of a peer’s relative status. Normative (“curved”) grading creates a situation in which peer-interactions are potentially competitive, but it is only those interactions with peers of a similar status that carry the potential for assistance to be costly to oneself. In two studies, we created hypothetical scenarios in which the grading practices (normative or absolute) and peer-status proximity (proximate, distant, or unknown) were manipulated, and asked participants to report their willingness to cooperate with a peer by sharing their notes from an important lecture. We found that when normative grading was used, individuals were less willing to assist a peer when they knew that the peer’s status was proximate to their own. There was also less cooperation when peer status was unknown, under normative grading, which is consistent with a risk-aversion tendency.     

Gender diversity and motivation in collaborative learning groups: the mediating role of group discussion quality

Collaborative learning is often used in higher education to help students develop their teamwork skills and acquire curricular knowledge. In this paper we test a mediation model in which the quality of group discussions mediates the impact of gender diversity and group motivation on collaborative learning effectiveness. Our results show that the proportion of women in groups, and the group level need for cognition and core self-evaluations (within group average) positively predict discussion quality that in turn predicts group (academic) performance. Our results show that discussion quality fully mediates the effects of need for cognition and core self-evaluations on group performance. The effect for gender diversity on group performance is only partly mediated by discussion quality.