Inspecting Visual Mental Images: Can People "See" Implicit Properties as Easily in Imagery and Perception?

Can people "see" previously unnoticed properties in objects that they visualize, or are they locked into the organization of the pattern that was encoded during perception? To answer this question, we first asked a group to describe letters of the alphabet and found that some properties (such as the presence of a diagonal line) are often mentioned, whereas others (such as symmetry) are rarely if ever mentioned. Then we showed not only that other participants could correctly detect both kinds of properties in visualized letters, but also that the relative differences in the ease of detecting these two types of properties are highly similar in perception (when the letters are actually visible) and imagery (when the letters are merely visualized). These findings provide support for the view that images can be reinterpreted in ways much like what occurs during perception and speak to the wider issue of the long-standing debate about the format of mental images.Psycholog

Gamification as a Sustainable Source of Enjoyment During Balance and Gait Exercises

We may be motivated to engage in a certain motor activity because it is instrumental to obtaining reward (e.g., money) or because we enjoy the activity, making it intrinsically rewarding. Enjoyment is related to intrinsic motivation which is considered to be a durable form of motivation. Therefore, many rehabilitation programs aim to increase task enjoyment by adding game elements (“gamification”). Here we ask how the influence of game elements on motivation develops over time and additionally explore whether enjoyment influences motor performance. We describe two different studies that varied game elements in different exercises. Experiment 1 compared the durability of enjoyment for a gamified and a conventional balance exercise in elderly. Experiment 2 addressed the question whether adding game elements to a gait adaptability exercise enhances the durability of enjoyment and additionally tested whether the game elements influenced movement vigor and accuracy (motor performance). The results show that the game elements enhanced enjoyment. Enjoyment faded over time, but this decrease tended to be less pronounced in gamified exercises. There was no evidence that the game elements affected movement vigor or accuracy

Reward-based motor adaptation can generalize across actions

Recently it has been shown that rewarded variability can be used to adapt visuomotor behavior. However, its relevance seems limited because adaptation to binary rewards has been demonstrated only when the same movement is repeated throughout the experiment. We therefore investigated whether the adaptation is action-specific and whether the amount of exploration depends on spatial complexity. Participants pointed to 3-D visual targets without seeing their hand and could use only binary reward feedback to adapt their movements. We varied the number of target positions and the number of dimensions the feedback was based on. Because the feedback was based on a 5-cm rightward shifted hand position, adaptation was needed for good performance. The participants started naïve to the perturbation. If actions were made toward a single target position and the feedback was based on the lateral component of their response only, participants adapted completely within 200 trials. Having more than 1 target position or more than 1 dimension of performance resulted in considerably less adaptation but did not affect the exploration. Thus, reward-based adaptation can generalize across actions but is reduced by spatial complexity, whereas exploration is not affected by spatial complexity

Uncertainty reveals surround modulation of shape

Noisy estimations of shape can be partially resolved by incorporating relevant information from the context. The effect of surround stimuli on shape perception becomes clear in illusions of shape contrast and assimilation. In this study, we answer the question how a surround-induced bias depends on the reliability of shape signals. This way, we assess the processes by which an observer incorporates relevant data from the context into the shape estimate. We selectively added visual noise to the center and surround and compared a bias in shape perception with a control condition where no noise was added. In the conditions where shape and surround stimuli were well defined, we found a shape-contrast bias. When the surround stimuli were degraded, this contrast bias decreased. Most interestingly, when the central shape was degraded, an assimilation bias was observed. This bias was larger when the entire stimulus was degraded compared to when only the central shape was degraded. This suggests that shape contrast is the result of inference processes relying on local representations in early visual areas whereas assimilation is related to inference processes by global representations in higher visual areas

Parental praise and children’s exploration: a virtual reality experiment

When children practice a new skill and fail, it is critical for them to explore new strategies to succeed. How can parents encourage children’s exploration? Bridging insights from developmental psychology and the neuroscience of motor control, we examined the effects of parental praise on children’s motor exploration. We theorize that modest praise can spark exploration. Unlike inflated praise, modest praise acknowledges children’s performance, without setting a high standard for future performance. This may be reassuring to children with lower levels of self-esteem, who often doubt their ability. We conducted a novel virtual-reality experiment. Children (N = 202, ages 8–12) reported self-esteem and performed a virtual-reality 3D trajectory-matching task, with success/failure feedback after each trial. Children received modest praise (“You did well!”), inflated praise (“You did incredibly well!”), or no praise from their parent. We measured motor exploration as children’s tendency to vary their movements following failure. Relative to no praise, modest praise—unlike inflated praise—encouraged exploration in children with lower levels of self-esteem. By contrast, modest praise discouraged exploration in children with higher levels of self-esteem. Effects were small yet robust. This experiment demonstrates that modest praise can spark exploration in children with lower levels of self-esteem

Perception of 3D shape in context: Contrast and assimilation

Whereas integration of shape and surround is held to occur through cue-dependent representations, we show that both cue-invariant and cue-dependent representations are involved. A central hinged plane and larger flanking plane were defined by either binocular disparity or motion. In a 'within-cue' condition, shape and surround were defined by the same cue and in a 'cross-cue' condition they were defined by a different cue. Observers compared the dihedral angle of the central shape with a constant reference. When the central shape was defined by disparity, the surround stimuli invoked a contrast bias in the within-cue condition, but shape assimilation occurred in the cross-cue condition. When the central shape was defined by motion there were overall no significant results, but if a contrast bias was observed, it was in the within-cue condition where integration could occur through cue-dependent representations

A review of grasping as the movements of digits in space

It is tempting to describe human reach-to-grasp movements in terms of two, more or less independent visuomotor channels, one relating hand transport to the object's location and the other relating grip aperture to the object's size. Our review of experimental work questions this framework for reasons that go beyond noting the dependence between the two channels. Both the lack of effect of size illusions on grip aperture and the finding that the variability in grip aperture does not depend on the object's size indicate that size information is not used to control grip aperture. An alternative is to describe grip formation as emerging from controlling the movements of the digits in space. Each digit's trajectory when grasping an object is remarkably similar to its trajectory when moving to tap the same position on its own. The similarity is also evident in the fast responses when the object is displaced. This review develops a new description of the speed-accuracy trade-off for multiple effectors that is applied to grasping. The most direct support for the digit-in-space framework is that prism-induced adaptation of each digit's tapping movements transfers to that digit's movements when grasping, leading to changes in grip aperture for adaptation in opposite directions for the two digits. We conclude that although grip aperture and hand transport are convenient variables to describe grasping, treating grasping as movements of the digits in space is a more suitable basis for understanding the neural control of grasping

Pitfalls in quantifying exploration in reward-based motor learning and how to avoid them

When learning a movement based on binary success information, one is more variable following failure than following success. Theoretically, the additional variability post-failure might reflect exploration of possibilities to obtain success. When average behavior is changing (as in learning), variability can be estimated from differences between subsequent movements. Can one estimate exploration reliably from such trial-to-trial changes when studying reward-based motor learning? To answer this question, we tried to reconstruct the exploration underlying learning as described by four existing reward-based motor learning models. We simulated learning for various learner and task characteristics. If we simply determined the additional change post-failure, estimates of exploration were sensitive to learner and task characteristics. We identified two pitfalls in quantifying exploration based on trial-to-trial changes. Firstly, performance-dependent feedback can cause correlated samples of motor noise and exploration on successful trials, which biases exploration estimates. Secondly, the trial relative to which trial-to-trial change is calculated may also contain exploration, which causes underestimation. As a solution, we developed the additional trial-to-trial change (ATTC) method. By moving the reference trial one trial back and subtracting trial-to-trial changes following specific sequences of trial outcomes, exploration can be estimated reliably for the three models that explore based on the outcome of only the previous trial. Since ATTC estimates are based on a selection of trial sequences, this method requires many trials. In conclusion, if exploration is a binary function of previous trial outcome, the ATTC method allows for a model-free quantification of exploration