Probabilistic models in human sensorimotor control

Sensory and motor uncertainty form a fundamental constraint on human sensorimotor control. Bayesian decision theory (BDT) has emerged as a unifying framework to understand how the central nervous system performs optimal estimation and control in the face of such uncertainty. BDT has two components: Bayesian statistics and decision theory. Here we review Bayesian statistics and show how it applies to estimating the state of the world and our own body. Recent results suggest that when learning novel tasks we are able to learn the statistical properties of both the world and our own sensory apparatus so as to perform estimation using Bayesian statistics. We review studies which suggest that humans can combine multiple sources of information to form maximum likelihood estimates, can incorporate prior beliefs about possible states of the world so as to generate maximum a posteriori estimates and can use Kalman filter-based processes to estimate time-varying states. Finally, we review Bayesian decision theory in motor control and how the central nervous system processes errors to determine loss functions and select optimal actions. We review results that suggest we plan movements based on statistics of our actions that result from signal-dependent noise on our motor outputs. Taken together these studies provide a statistical framework for how the motor system performs in the presence of uncertainty.     

Fidgeting as self-evidencing: A predictive processing account of non-goal-directed action

Non-goal-directed actions have been relatively neglected in cognitive science, but are ubiquitous and related to important cognitive functions. Fidgeting is seemingly one subtype of non-goal-directed action which is ripe for a functional account. What's the point of fidgeting? The predictive processing framework is a parsimonious account of brain function which says the brain aims to minimise the difference between expected and actual states of the world and itself, that is, minimise prediction error. This framework situates action selection in terms of active inference for expected states. However, seemingly aimless, idle actions, such as fidgeting, are a challenge to such theories. When our actions are not obviously goal-achieving, how can a predictive processing framework explain why we regularly do them anyway? Here, we argue that in a predictive processing framework, evidence for the agent's own existence is consolidated by self-stimulation or fidgeting. Endogenous, repetitive actions reduce uncertainty about the system's own states, and thus help continuously maintain expected rates of prediction error minimisation. We extend this explanation to clinically distinctive self-stimulation, such as in Autism Spectrum Conditions, in which effective strategies for self-evidencing may be different to the neurotypical case.     

Tracking without perceiving: a dissociation between eye movements and motion perception

Can people react to objects in their visual field that they do not consciously perceive? We investigated how visual perception and motor action respond to moving objects whose visibility is reduced, and we found a dissociation between motion processing for perception and for action. We compared motion perception and eye movements evoked by two orthogonally drifting gratings, each presented separately to a different eye. The strength of each monocular grating was manipulated by inducing adaptation to one grating prior to the presentation of both gratings. Reflexive eye movements tracked the vector average of both gratings (pattern motion) even though perceptual responses followed one motion direction exclusively (component motion). Observers almost never perceived pattern motion. This dissociation implies the existence of visual-motion signals that guide eye movements in the absence of a corresponding conscious percept.     

From cooperation to conflict: The role of collective narratives in shaping group behaviour

In this paper, we review the concept of collective narratives and their role in shaping group behaviour. We see collective narratives as ‘meta-stories’ embraced by groups that incorporate values and beliefs about social reality, therefore providing a blueprint for group norms which, in turn, inform group members' behaviour. Our aim is to both describe the psychological processes underpinning the relation between collective narratives and group behaviours and develop an integrative typology of the functions of collective narratives (as they connect to various collective behaviours). We start by discussing definitions in the recent literature and propose an integrative conceptualisation which positions collective narratives in the context of collective action research. Next, we focus on the process by which collective narratives provide the bases for identity formation, development, and change, thus shaping group behaviour. We see collective narratives as central in understanding group behaviour, as they function as ‘meta-stories’ that incorporate moral codes and values, and beliefs about the ingroups and outgroups—providing a blueprint for group norms which, in turn, inform group members' behaviour. In the second part of the article, we describe a typology of collective narratives according to their functions, structured around two core dimensions: the context/s in which collective narratives develop and are shared (i.e., intragroup vs. intergroup) and their effects within these contexts (i.e., driving consensus vs. driving dissent). We identify four distinctive types of collective narrative functions and review research showing how each of them shapes specific social identity content, including behaviour prescribing norms. We then show how these specific norms shape behaviours ranging from cooperation and pro-social action to hostile intergroup conflict. The implications of this contribution are twofold. First, by providing a systematic account and categorisation of how collective narratives function in society and of their connections to social identities (and their content), we can more accurately deduct group norms and predict behaviours in specific circumstances, including in relation to political violence. Second, by better understanding the narratives that provide the bases of identity formation, development, and change, we can improve attempts to create alternative narratives that unify rather than divide people, so that pathways to co-operation might be chosen over conflict.     

Intentionality and temporal binding: Do causality beliefs increase the perceived temporal attraction between events?

Intentional motor actions and their effects are bound together in temporal perception, resulting in the so-called intentional binding effect. In the current study, we address an alternative explanatory mechanism for the emergence of temporal binding by excluding the role of motor action. Employing a sensory-based Libet clock paradigm, we examined temporal perception of two different auditory stimuli, and tested the influence of beliefs about the causal relationship between the two auditory stimuli, thus simulating a crucial feature of intentional action. In two experiments, we found a robust temporal repulsion effect, indicating that instead of being attracted to each other, the auditory stimuli were shifted away from each other in temporal perception. Interestingly, repulsion was attenuated by causal beliefs, but this effect was fragile. Furthermore, temporal repulsion was unaffected by the intensity of prior learning. Findings are discussed in the context of intentional action awareness research and multisensory integration.     

Effects of Non-conformity on Perceived Status and Competence: Examining the Moderating Role of Physical Attractiveness

The present study attempts to examine how people perceive non-conforming behaviour and what do they infer about subjects who demonstrate non-conformity. Interviews were conducted to determine the operational definition and perception about non-conformity. Analysis of the interviews revealed that non-conformity is attributed to not abiding by the rules that have been defined or laid out by an authority in a particular context. Scenario-based experiments were conducted, and the obtained data were analysed to reach a conclusion regarding observers’ perception about non-conforming individuals in a collectivist culture. The results showed that non-conforming behaviour leads to a negative inference about status and competence. Also, we found that the attractiveness of non-conforming individuals does not lessen the negative inferences derived by the observers in a collectivist culture. The findings can be extended to devise several communication and signalling strategies to influence the mass behaviour in a collectivist culture, like India. The study provides us insights about achieving social objectives as well as driving behavioural change in a collectivist context.     

Problems with persistence

A fundamental question in reasoning about change is, what information does a reasoning agent infer about later times from earlier times? I will argue that reasoning about change by an agent is to be modeled in terms of the persistence of the agent's beliefs over time rather than the persistence of truth and that such persistence is explained by pragmatic factors about how agents acquire information from other agents rather than by general principles of persistence about states of the world. AI accounts of persistence have focused on ‘closed world’ examples of change, in which the agent believes that the truth of a proposition is unaltered so long as he or she has no evidence that it has been changed. AI principles of persistence seem plausible in a closed world where one assumes the agent knows everything that is happening. If one drops the assumption of omniscience, however, the analysis of persistence is implausible. To get a good account of persistence and reasoning about change, I argue we should examine ‘open world’ examples of change, in which the agent is ignorant of some of the changes occurring in the world. In open world examples of change, persistence must be formulated, I argue, as a pragmatic principle about the persistence of beliefs. After elaborating my criticisms of current accounts of persistence, I examine how such pragmatic principles fare with the notorious examples of reasoning about action that have collectively characterized the so-called frame problem.     

Phenomenal evidence and factive evidence

Perceptions guide our actions and provide us with evidence of the world around us. Illusions and hallucinations can mislead us: they may prompt as to act in ways that do not mesh with the world around us and they may lead us to form false beliefs about that world. The capacity view provides an account of evidence that does justice to these two facts. It shows in virtue of what illusions and hallucinations mislead us and prompt us to act. Moreover, it shows in virtue of what we are in a better epistemic position when we perceive than when we hallucination. In this paper, I develop the capacity view, that is, the view that perceptual experience has epistemic force in virtue of the epistemic and metaphysical primacy of the perceptual capacities employed in perception. By grounding the epistemic force of experience in facts about the metaphysical structure of experience, the capacity view is not only an externalist view, but moreover a naturalistic view of the epistemology of perceptual experience. So it is an externalist and naturalistic alternative to reliabilism. I discuss the repercussions of this view for the justification of beliefs and the epistemic transparency of mental states, as well as, familiar problem cases.     

The Representationalism versus Relationalism Debate: Explanatory Contextualism about Perception

There are two very different ways of thinking about perception. According to representationalism, perceptual states are representations: they represent the world as being a certain way. They have content, which may or may not be different from the content of beliefs. They represent objects as having properties, sometimes veridically, sometimes not. According to relationalism, perception is a relation between the agent and the perceived object. Perceived objects are literally constituents of our perceptual states and not of the contents thereof. Perceptual states are not representations. My aim is to argue that if we frame this debate as a debate about the individuation of perceptual states, rather than the nature of perception, then we can reconcile these two seemingly conflicting ways of thinking about perception.     

Rôle des propriétés inertielles segmentaires sur la perception de l’étendue de l’espace péripersonnel

Previous studies have suggested that the perception of peripersonal space can hardly be achieved using only scene-based visual cues and requires combining visual information with motor representations. Motor representation can be viewed as a component of a predictive system, which includes a neural process that simulates through motor imagery the dynamic behaviour of the body in relation to the environment. In this study, we analysed whether modifying the force required to reach a visual target influences the perception of what is reachable. In a visuomotor task, the experimental group (n = 10) adapted to a 1.5 kg weight attached to the right wrist while performing a series of pointing movements. The control group (n = 10) performed the motor task without inertial perturbation. A perceptual judgement task of what is reachable was performed before and after the motor task. Results showed that inertial perturbation produced initially an undershoot of the target suggesting a lack of motor force to overcome the inertial perturbation, but spatial errors receded progressively through movement rehearsal. Perceptual estimates of what is reachable slightly overestimated action capacities but were not affected by motor adaptation. Thus, modifying motor force required to compensate for inertial perturbation had no direct effect on the perception of peripersonal space. When interpreted in regard to previous experimental work, this result suggests that motor representations may provide information about the sensory or spatial consequences of action rather than the sense of effort associated with motor production.     

Explaining Normative Versus Nonnormative Action: The Role of Implicit Theories

The current research investigates what motivates people to engage in normative versus nonnormative action. Prior research has shown that different emotions lead to different types of action. We argue that these differing emotions are determined by a more basic characteristic, namely, implicit theories about whether groups and the world in general can change. We hypothesized that incremental theories (beliefs that groups/the world can change) would predict normative action, and entity theories (beliefs that groups/the world cannot change) as well as group identification would predict nonnormative action. We conducted a pilot in the context of protests against a government plan to relocate Bedouin villages in Israel and a main study during the Israeli social protests of the middle class. Results revealed three distinct pathways to collective action. First, incremental theories about the world predicted hope, which predicted normative action. Second, incremental theories about groups and group identification predicted anger, which also predicted normative collective action. Lastly, entity theories about groups predicted nonnormative collective action through hatred, but only for participants who were highly identified with the group. In sum, people who believed in the possibility of change supported normative action, whereas those who believed change was not possible supported nonnormative action.     

Second-order beliefs about intention and children's attributions of sociomoral judgment

Predicting how another person will evaluate the intention underlying an action involves consideration of second-order mental states. Children (ages 5-10 years) and college students (N=105) predicted an observer's belief about an actor's intention and evaluated the actor from both their own perspectives and the perspective of the observer. Younger children were more likely than older children and adults to attribute a belief to the observer that mismatched the actor's prior intention. Attributed beliefs about intention were more likely to match negative prior intentions than to match positive prior intentions and were also more likely to match prior intentions when the observer knew the actor's prior intention than when the observer did not know the actor's prior intention. The judgments attributed to the observer were based on the beliefs about intention attributed to the observer, showing use of second-order mental states to infer another's sociomoral judgments.     

The valence of action outcomes modulates the perception of one's actions

When interacting with the world, we need to distinguish whether sensory information results from external events or from our own actions. The nervous system most likely draws this distinction by comparing the actual sensory input with an internal prediction about the sensory consequences of one's actions. However, interacting with the world also requires an evaluation of the outcomes of self-action, e.g. in terms of their affective valence. Here we show that subjects' perceived pointing direction does not only depend on predictive and sensory signals related to the performed action itself, but also on the affective valence of the action outcome: subjects perceived their movements as directed towards positive and away from negative outcomes. Our findings suggest that the non-conceptual perception of the sensory consequences of self-action builds on both sensorimotor information related directly to self-action and a post hoc evaluation of the affective action outcome.     

Action understanding as inverse planning

Humans are adept at inferring the mental states underlying other agents’ actions, such as goals, beliefs, desires, emotions and other thoughts. We propose a computational framework based on Bayesian inverse planning for modeling human action understanding. The framework represents an intuitive theory of intentional agents’ behavior based on the principle of rationality: the expectation that agents will plan approximately rationally to achieve their goals, given their beliefs about the world. The mental states that caused an agent’s behavior are inferred by inverting this model of rational planning using Bayesian inference, integrating the likelihood of the observed actions with the prior over mental states. This approach formalizes in precise probabilistic terms the essence of previous qualitative approaches to action understanding based on an “intentional stance” [Dennett, D. C. (1987). The intentional stance. Cambridge, MA: MIT Press] or a “teleological stance” [Gergely, G., Nádasdy, Z., Csibra, G., & Biró, S. (1995). Taking the intentional stance at 12 months of age. Cognition, 56, 165-193]. In three psychophysical experiments using animated stimuli of agents moving in simple mazes, we assess how well different inverse planning models based on different goal priors can predict human goal inferences. The results provide quantitative evidence for an approximately rational inference mechanism in human goal inference within our simplified stimulus paradigm, and for the flexible nature of goal representations that human observers can adopt. We discuss the implications of our experimental results for human action understanding in real-world contexts, and suggest how our framework might be extended to capture other kinds of mental state inferences, such as inferences about beliefs, or inferring whether an entity is an intentional agent.     

Action-dependent perceptual invariants: from ecological to sensorimotor approaches

Ecological and sensorimotor theories of perception build on the notion of action-dependent invariants as the basic structures underlying perceptual capacities. In this paper we contrast the assumptions these theories make on the nature of perceptual information modulated by action. By focusing on the question, how movement specifies perceptual information, we show that ecological and sensorimotor theories endorse substantially different views about the role of action in perception. In particular we argue that ecological invariants are characterized with reference to transformations produced in the sensory array by movement: such invariants are transformation-specific but do not imply motor-specificity. In contrast, sensorimotor theories assume that perceptual invariants are intrinsically tied to specific movements. We show that this difference leads to different empirical predictions and we submit that the distinction between motor equivalence and motor-specificity needs further clarification in order to provide a more constrained account of action/perception relations.     

On Direct Social Perception

Direct Social Perception (DSP) is the idea that we can non-inferentially perceive others’ mental states. In this paper, I argue that the standard way of framing DSP leaves the debate at an impasse. I suggest two alternative interpretations of the idea that we see others’ mental states: others’ mental states are represented in the content of our perception, and we have basic perceptual beliefs about others’ mental states. I argue that the latter interpretation of DSP is more promising and examine the kinds of mental states that plausibly could satisfy this version of DSP.     

An investigation of the determinants of motor contagion in preschool children

The influence of action perception on action execution has been demonstrated by studies of motor contagion in which the observation of an action interferes with the concurrent execution of a different action. The current study extends prior work on the extent of motor contagion in early childhood, a period of development when the effects of action observation on action execution may be particularly salient. During a classroom story reading, children (mean age 4.8 years) were familiarized with two different-colored bears, one of which was used as a seemingly animate hand puppet while the other bear remained lifeless and inanimate. Children then completed a task in which they were instructed to move a stylus on a graphics tablet in the presence of background videos of each bear making horizontal arm movements which had biological (human-moved) or non-biological (machine-moved) origins. Motor contagion was assessed as the variability of stylus movements in the horizontal axis when children were instructed to produce vertical stylus movements. Significant levels of motor contagion were seen when children observed the previously animate bear in the non-biological motion condition and when they observed the previously inanimate bear in the biological motion condition. For future studies of social perception, this finding points to the potential importance of examining mismatches between prior experience with (or knowledge about) a particular agent and the subsequent behavior of that agent in a different context.     

The influence of just-world beliefs on driving anger and aggressive driving intentions

Decades of research demonstrate that the extent to which one believes the world is just can have important interpersonal consequences. Unfortunately, most of the commonly studied consequences are negative in nature. Guided by previous research demonstrating the buffering effect of just‐world beliefs and anger, the present research explores how belief in a just world (BJW) may mitigate anger in the domain of driving anger and examines the limiting conditions of this effect. Study 1 demonstrated the expected negative relation between common measures of BJW and anger expression in a driving context. Study 2 found that the buffering effects of just‐world beliefs and driver aggression were greater when BJW was violated (vs. not). Study 3 replicated the effects on aggression and anger and established a mediational role of anger on the buffering effects of just‐world beliefs on thoughts and driver aggression. Aggr. Behav. 38:389‐402, 2012. © 2012 Wiley Periodicals, Inc.     

Eye movements and scene perception.

Research on eye movements and scene perception is reviewed. Following an initial discussion of some basic facts about eye movements and perception, the following topics are discussed: (I) the span of effective vision during scene perception, (2) the role of eye movements in scene perception, (3) integration of information across saccades, (4) scene context, object identification and eye movements, and (5) the control of eye movements. The relationship of eye movements during reading to eye movements during scene perception is considered. A preliminary model of eye movement control in scene perception is described and directions for future research are suggested.