Effects of motor congruence on visual working memory

Grounded-cognition theories suggest that memory shares processing resources with perception and action. The motor system could be used to help memorize visual objects. In two experiments, we tested the hypothesis that people use motor affordances to maintain object representations in working memory. Participants performed a working memory task on photographs of manipulable and nonmanipulable objects. The manipulable objects were objects that required either a precision grip (i.e., small items) or a power grip (i.e., large items) to use. A concurrent motor task that could be congruent or incongruent with the manipulable objects caused no difference in working memory performance relative to nonmanipulable objects. Moreover, the precision- or power-grip motor task did not affect memory performance on small and large items differently. These findings suggest that the motor system plays no part in visual working memory.     

Effects of task constraint on action dynamics

The actualization of action possibilities (i.e., affordances) can often be accomplished in numerous ways. For instance, an individual could walk over to a rubbish bin to drop an item in or throw the piece of rubbish into the bin from some distance away. The aim of the current study was to investigate the action dynamics that emerge from such under-constrained task or action spaces using an object transportation task. Participants were instructed to transport balls between a starting location and a large wooden box located 9 m away. The temporal interval between the sequential presentation of balls was manipulated as a control parameter and was expected to influence the distance participants moved prior to throwing or dropping the ball into the target box. A two-parameter state space derived from the Cusp Catastrophe Model was employed to illustrate how behavioral variability emerged as a consequence of the under-constrained task context. Two follow-up experiments demonstrated direct correspondence between model predictions and observed action dynamics as a function of increasing task constraints. Implications for modeling, the theory of affordances, and empirical studies more generally are discussed.     

Detection of collision events on curved trajectories: optical information from invariant rate-of-bearing change

Previous research (Andersen & Kim, 2001) has shown that a linear trajectory collision event (i.e., a collision between a moving object and an observer) is specified by objects that expand and maintain a constant bearing (the object location remains constant in the visual field). In the present study, we examined the optical information for detecting a collision event when the trajectory was of constant curvature. Under these conditions, a collision event is specified by expansion of an object and a constant rate-of-bearing change. Three experiments were conducted in which trajectory curvature and display duration were varied while time to contact, speed, and initial image position of the collision objects were maintained. The results indicated that collision detection performance decreased with an increase in trajectory curvature and decreased with a decrease in display duration, especially for highly curved trajectories. In Experiment 3, we found that the presentation of a constant rate-of-bearing change in noncollision stimuli resulted in an increase in the false alarm rate. These results demonstrate that observers can detect collision events on curved trajectories and that observers utilize bearing change information.     

Neurobiological degeneracy: Supporting stability,flexibility and pluripotentiality in complex motor skill

This paper investigated neurobiological degeneracy of the motor system that emerged as a function of levels of environmental constraint. Fourteen participants performed a breaststroke-swimming task that required them to develop a specific biomechanically expert pattern and in turn provide the basis for a suitable task vehicle to study the functional role of movement variability. Inter-limb coordination was defined based on the computation of continuous relative phase between elbow and knee oscillators. Unsupervised cluster analysis on arm–leg coordination revealed the existence of different patterns of coordination when participants achieved the same task goal under different levels of environmental constraints (i.e. different amounts of forward resistances). In addition, clusters differed in terms of higher order derivatives (e.g., joint angular velocity, joint amplitude), suggesting an effective role for degeneracy in learning by allowing the exploration of the key relationships between motor organization and interacting constraints. There is evidence to suggest that neurobiological degeneracy supports the potential for motor re-organization to enhance motor learning.     

The multifaceted nature of unsupervised category learning

A substantial portion of category-learning research has focused on one learning mode--namely, classification learning (a supervised learning mode). Subsequently, theories of category learning have focused on how the abstract structure of categories (i.e., the co-occurrence patterns of feature values) affects acquisition. Recent work in supervised learning has shown that a learner's interactions with the stimulus set also plays an important role in acquisition. The present study extends this work to unsupervised learning situations involving simple one-dimensional stimuli. The results suggest that categorization performance is a function of both learning mode (i.e., study conditions) and learning problem (i.e., category structure). Unsupervised learning, like supervised learning, appears to be multifaceted, with different learning modes best paired with certain learning problems.     

Induction of combination rules in two-dimensional function learning

Previous studies have typically found that when people learn to combine two dimensions of a stimulus to select a response, they learn additive combination rules more easily than nonadditive (e.g., multiplicative) ones. The present experiments demonstrate that in some situations people can learn multiplicative rules more easily than other (e.g., additive) rules. Subjects learned to produce specified response durations when presented with stimulus lines varying in length and angle of orientation. When stimuliand correct responses were related by a multiplicative combination of power functions, learning was relatively easy (Experiment 1). In contrast, systematic response biases occurred during the early phases of learning an additive combination of linear functions (Experiment 2) and a more complex (nonadditive and nonmultiplicative) combination of linear functions (Experiment3), suggesting that people have a tendency to induce a multiplicative combination of power functions. However, the initial biases decreased with practice. These results are explained in terms of a revised adaptive regression model of function learning originally proposed by Koh and Meyer (1991). Differences between the present results and previous results in the literature are discussed.     

The weight of time: affordances for an integrated magnitude system

In five experiments we explored the effects of weight on time in different action contexts to test the hypothesis that an integrated magnitude system is tuned to affordances. Larger magnitudes generally seem longer; however, Lu and colleagues (2009) found that if numbers were presented as weights in a range heavy enough to affect lifting, the "larger seems longer" effect was enhanced, but it was eliminated with weights too light to affect lifting. Experiments 1 and 2 revealed that actually lifting kilogram and gram weights had effects parallel to symbolized weights, suggesting that Lu et al.'s task implicitly evoked a lifting context. Experiments 3 and 4 showed that weights too heavy (e.g., tons) or too light to be discriminated by lifting, but relevant to other affordances (e.g., grams of a toxin) had effects on time as large or larger than for kilograms. Experiment 5 showed that the effect for grams in a toxicology context did not generalize to the lifting task of Experiment 2. Weight appears to integrate with other magnitudes when it is relevant to meaningful actions, including but not limited to lifting.     

Dynamic Occlusion and Optical Flow From Corrugated Surfaces

Dynamic occlusion (i.e., accretion and deletion of optical texture at the occluding edge) can occur under many different environmental conditions, for example, objects hidden behind other objects when viewed by a moving observer, objects moving in front of other objects, or an observer approaching a brink. Because each of these conditions may require the actor to respond differently, the actor may need to be able to differentiate these situations reliably. This study was directed at the optical pattern induced by dynamic occlusion that occurs when one locomotes over a rolling terrain (i.e., a corrugated surface). Two experiments were conducted for this purpose. Participants viewed displays simulating their translation along a corrugated surface in which surface corrugation, texture type, and texture density varied as part of experimental control. Results demonstrated that the visual system reliably extracts the global flow pattern for accurate perception of heading direction despite the presence of optical disturbances in optical flow. However, performance nearly failed in the unstructured texture displays wherein optical disturbances were less salient. Still, the results provide strong evidence that human observers are sufficiently sensitive to dynamic occlusion to extract information about heading direction.     

The influence of athletic experience and kinematic information on skill-relevant affordance perception

Humans can perceive affordances both for themselves and for others, and affordance perception is a function of perceptual–motor experience involved in playing a sport. Two experiments investigated the enhanced affordance perception of athletes. In Experiment 1, basketball players and nonbasketball players provided perceptual reports for sports-relevant (maximum standing-reach and reach-with-jump heights) and non-sports-relevant (maximum sitting height) affordances for self and other. Basketball players were more accurate at perceiving maximum reach-with-jump for another person than were nonbasketball players, but were no better at perceiving maximum reach or sitting heights. Experiment 2 investigated the informational basis for this enhanced perceptual ability of basketball players by evaluating whether kinematics inform perceivers about action-scaled (e.g., force-production dependent), but not body-scaled (i.e., geometrically determined), affordances for others, and whether basketball experience enhances sensitivity to kinematic information. Only basketball players improved at perceiving an action-scaled affordance (maximum reach-with-jump), but not body-scaled affordances (maximum standing-reach and sit) with exposure to kinematic information, suggesting that action-scaled affordances may be specified by kinematic information to which athletes are already attuned by virtue of their sport experience.     

The influence of athletic experience and kinematic information on skill-relevant affordance perception

Humans can perceive affordances both for themselves and for others, and affordance perception is a function of perceptual-motor experience involved in playing a sport. Two experiments investigated the enhanced affordance perception of athletes. In Experiment 1, basketball players and nonbasketball players provided perceptual reports for sports-relevant (maximum standing-reach and reach-with-jump heights) and non-sports-relevant (maximum sitting height) affordances for self and other. Basketball players were more accurate at perceiving maximum reach-with-jump for another person than were nonbasketball players, but were no better at perceiving maximum reach or sitting heights. Experiment 2 investigated the informational basis for this enhanced perceptual ability of basketball players by evaluating whether kinematics inform perceivers about action-scaled (e.g., force-production dependent), but not body-scaled (i.e., geometrically determined), affordances for others, and whether basketball experience enhances sensitivity to kinematic information. Only basketball players improved at perceiving an action-scaled affordance (maximum reach-with-jump), but not body-scaled affordances (maximum standing-reach and sit) with exposure to kinematic information, suggesting that action-scaled affordances may be specified by kinematic information to which athletes are already attuned by virtue of their sport experience.     

Orienting Under Load: Intrinsic Dynamics and Postural Affordances for Visual Perception

Orientation toward one's surroundings is necessary for prospective control of action, and constraints on orienting activity have consequences for animal survival. Physically coupled load is a constraint for humans wearing protective equipment (firefighters, soldiers, etc.). The consequences of load on postural affordances while transitioning to upright stance was used to quantify the impact of different soldier configurations. Eight participants established upright posture in 4 relevant load configurations (5.0 to 79.2 lb). Load affected the accessibility of optical information at a distance as evidenced by increasing downward head angles and reductions in postural coordination. Reductions in the variability of time to establish upright stance with load suggests a loss of functional adaptability. Load asymmetries played a significant role as the most asymmetric configuration (not the heaviest) had the most detrimental effect on postural affordances. Center of Pressure (CoP) dynamics reflected the consequences of asymmetric loading on postural regulation as greater power and fluctuations across frequencies were observed. Physically coupled load induces significant constraints on orienting activity, and load asymmetry contributes significantly to the detrimental effects of protective equipment on action-perception coupling during whole-body movements.     

Individual differences in causal learning and decision making

In judgment and decision making tasks, people tend to neglect the overall frequency of base-rates when they estimate the probability of an event; this is known as the base-rate fallacy. In causal learning, despite people's accuracy at judging causal strength according to one or other normative model (i.e., Power PC, DeltaP), they tend to misperceive base-rate information (e.g., the cause density effect). The present study investigates the relationship between causal learning and decision making by asking whether people weight base-rate information in the same way when estimating causal strength and when making judgments or inferences about the likelihood of an event. The results suggest that people differ according to the weight they place on base-rate information, but the way individuals do this is consistent across causal and decision making tasks. We interpret the results as reflecting a tendency to differentially weight base-rate information which generalizes to a variety of tasks. Additionally, this study provides evidence that causal learning and decision making share some component processes.     

Contrast and Rater-Perspective Effects on Judgments of Sexual Harassment Severity: What He Thinks She Thinks,and Vice Versa

We looked at whether ratings biases can influence judgments people make about sexually harassing behaviors. Online participants (N = 176) read and rated the severity of complaint scenarios describing different incidents of alleged harassment. We manipulated: (1) contrast effects, by having people judge other, independent scenarios before judging a target scenario, and (2) rater-perspective effects, by having people judge from both a self- and then an opposite-gender perspective. For the former, we hypothesized that if judgments about harassment are qualitatively similar to judgments made in other areas (e.g., performance appraisal), they too should show contrast effects. For the latter, we hypothesized people would use stereotypes about the other gender, thereby overestimating the true (i.e., self-perspective driven) gender difference. Results supported both hypotheses, suggesting that decision makers should be aware of the possible influence of biases when judging whether behaviors constitute harassment.     

TRoPICALS: a computational embodied neuroscience model of compatibility effects

Perceiving objects activates the representation of their affordances. For example, experiments on compatibility effects showed that categorizing objects by producing certain handgrips (power or precision) is faster if the requested responses are compatible with the affordance elicited by the size of objects (e.g., small or large). The article presents a neural-network architecture that provides a general framework to account for compatibility effects. The model was designed with a methodological approach (computational embodied neuroscience) that aims to provide increasingly general accounts of brain and behavior (4 sources of constraints are used: neuroscientific data, behavioral data, embodied systems, reproduction of learning processes). The model is based on 4 principles of brain organization that we claim underlie most compatibility effects. First, visual perception and action are organized in the brain along a dorsal neural pathway encoding affordances and a ventral pathway encoding goals. Second, the prefrontal cortex within the ventral pathway gives a top-down bias to action selection by integrating information on stimuli, context, and goals. Third, reaction times depend on dynamic neural competitions for action selection that integrate bottom-up and top-down information. The congruence or incongruence between affordances and goals explains the different reaction times found in the experiments. Fourth, as words trigger internal simulations of their referents, they can cause compatibility effects as objects do. We validated the model by reproducing and explaining 3 types of compatibility effects and showed its heuristic power by producing 2 testable predictions. We also assessed the explicative power of the model by comparing it with related models and showed how it can be extended to account for other compatibility effects.     

On the dominance of unidimensional rules in unsupervised categorization.

In several experiments, observers tried to categorize stimuli constructed from two separable stimulus dimensions in the absence of any trial-by-trial feedback. In all of the experiments, the observers were told the number of categories (i.e., two), they were told that perfect accuracy was possible, and they were given extensive experience in the task (i.e., 800 trials). When the boundary separating the contrasting categories was unidimensional, the accuracy of all observers improved significantly over blocks (i.e., learning occurred), and all observers eventually responded optimally. When the optimal boundary was diagonal, none of the observers responded optimally. Instead they all used some sort of suboptimal unidimensional rule. In a separate feedback experiment, all observers responded optimally in the diagonal condition. These results contrast with those for supervised category learning; they support the hypothesis that in the absence of feedback, people are constrained to use unidimensional rules.     

On the dominance of unidimensional rules in unsupervised categorization

In several experiments, observers tried to categorize stimuli constructed from two separable stimulus dimensions in the absence of any trial-by-trial feedback. In all of the experiments, the observers were told the number of categories (i.e., two), they were told that perfect accuracy was possible, and they were given extensive experience in the task (i.e., 800 trials). When the boundary separating the contrasting categories was umdimensional, the accuracy of all observers improved significantly over blocks (i.e., learning occurred), and all observers eventually responded optimally. When the optimal boundary was diagonal, none of the observers responded optimally. Instead they all used some sort of suboptimal unidimensional rule. In a separate feedback experiment, all observers responded optimally in the diagonal condition. These results contrast with those for supervised category learning; they support the hypothesis that in the absence of feedback, people are constrained to use unidimensional rules.     

Exploration evoked by the environment is balanced by the need to perform in cricket spin bowling.

In the theory of ecological dynamics, adaptive responses emerge through exploration when an individual interacts with their environment. This study investigates how when competing, the environment guides perceptual-motor exploration that is balanced by the need to meet performance requirements. To understand this, eight emerging expert cricket spin bowlers aged 21 ± 3 years competed in three small-sided simulated practice matches where pitch conditions were manipulated to present familiar and unfamiliar environmental pitch constraints. It was hypothesized that bowlers would explore the unfamiliar pitch by searching for an action mode that allowed them to best exploit the conditions to achieve a successful outcome (e.g., take a wicket) while simultaneously attempting to satisfy the immediate performance requirements (e.g., limit runs per over). A mixed methodology was used to first identify the perceptions and intentions of the bowlers (dimensions, themes, and action modes), followed by analysis of the resultant action characteristics (delivery speed, spin rate, and pitching position) and performance outcomes (economy rate, strike rate, and bowling average). Overall, when competing on the familiar pitch, the bowlers reported primarily attuning to task constraints (75%). In contrast, when bowling on the unfamiliar pitch, all bowlers reported that their attention was more focused upon picking up key affordances related to environmental pitch constraints (100%). The majority of bowlers indicated that they bowled differently on the unfamiliar pitch by using more “side-spin” and less “over-spin”. Interestingly, it was not until the second performance on this pitch that execution variables significantly changed. Despite these changes, bowlers continued to pay attention to the opposing batters’ strategies throughout all three practice matches. The consistency of this response can be explained by an overarching strategy for all types of bowling in cricket that is more closely linked to the ongoing individual-opponent interaction. That is, the bowlers must perform and ‘stay in the game’ whilst simultaneously adapting to any environmental changes. Therefore, demonstrating the need to continually satisfy the immediate performance requirements to afford the opportunity to explore new affordances in the environment that may offer exploitation.     

The Separation of Action and Perception and the Issue of Affordances

Michaels's (2000) reassessment of the relation between action and perception is endorsed. In alignment with Milner and Goodale (1995), she proposed a separation between action (i.e., control of movement) and perception (i.e., the explicit knowledge of environmental properties, including animal-referential ones), the separation being based on the reliance on different optical variables. However, how should the concept of affordances be incorporated into this scheme? We present data showing that affordances, both when perceived and acted on, are not susceptible to optical illusions. Because action and perception are distinguished on the basis of information used, but are also proposed to interact, it is hypothesized that, dependent on the task goal, "information for action" may be used in perception, and "information for perception" may be used in action. Participants may become more attuned to information for action when perception serves to acquire explicit knowledge about what the environment affords for action.     

Encoding time and signs exposure time in the representation of diagrammatic deontic meanings

It has been proposed that prohibition and obligation be represented in different ways in reasoning with deontic information (Bucciarelli & Johnson-Laird, 2005). Obligations are salient in permissible situations and prohibitions in impermissible situations. In some specific cases, differential initial representations are also consistently predicted from the comprehension of negations, if prohibition is considered as the negation of an obligation. Three experiments evaluate whether traffic signs of prohibition and obligation speed up the response time to the proposed direction represented and whether this advantage remains when people have more time to think. When making judgements about the manoeuvre performed by a vehicle, participants' response times are consistent with the predicted representation when they have a short time (i.e., 300 ms) to understand the premise. In this case they represent what is permissible by obligatory signs and also what is impermissible by prohibitory signs. However, if they have more time (i.e., 1000 ms) to understand the premise, they still represent what is permissible by obligatory signs but they seem to change their initial representations to what is permissible by prohibitory signs.     

Sacrifice in close relationships: Motives,emotions, and relationship outcomes

Romantic partners often face situations in which their preferences, interests and goals are not well aligned—what is good for one partner is not good for the other. In these situations, people need to make a decision between pursuing their own self‐interest and sacrificing for their partner or the relationship. In this work, we discuss antecedents and consequences of sacrifice in close relationships. Specifically, we address when people are more likely to sacrifice, what are the motivations driving a sacrifice, and what are the affective consequences of this behavior for the person who makes the sacrifice (i.e., the actor), for the person who receives the sacrifice (i.e., the recipient), and for the relationship. We conclude by discussing important directions for future research on the implications of sacrifice for the well‐being of individuals and their relationships.