Interference with memory for lifted weight

An adaptation-level model for memory was tested by interpolating different weights between the standard and comparison weights. The results suggest that the model should be modified to account for the general tendency to use alternative categories of judgment with equal frequency. In terms of the modified model, memory for the standard shifts toward the value of the interfering stimulus, the magnitude of shift being proportional to the difference between the interfering stimulus and the value the memory would otherwise have had.     

Online versus offline processing of visual feedback in the control of movement amplitude

Researchers have suggested that visual feedback not only plays a role in the correction of errors during movement execution but that visual feedback from a completed movement is processed offline to improve programming on upcoming trials. In the present study, we examined the potential contribution of online and offline processing of visual feedback by analysing spatial variability at various kinematic landmarks in the limb trajectory (peak acceleration, peak velocity, peak negative acceleration and movement end). Participants performed a single degree of freedom video aiming task with and without vision of the cursor under four criterion movement times (225, 300, 375 and 450 ms). For movement times of 225 and 300 ms, the full vision condition was less variable than the no vision condition. However, the form of the variability profiles did not differ between visual conditions suggesting that the contribution of visual feedback was due to offline processes. In the 375 and 450 ms conditions, there was evidence for both online and offline control as the form of the variability profiles differed significantly between visual conditions.     

Influence of different modes of real time visual information on single aimed movements

This study shows that the difference in appearance between two types of computer generated real time visual information namely, cursor and trace feedback, becomes visible in the execution of aimed stylus movements. Movement execution was scrutinized by division into four relevant subsequent constituents on the basis of key kinematic events. As expected, the final section of a movement took more time and showed a larger number of adjustments in the cursor condition. Instead, the influence of trace feedback on movement execution became discernible in earlier sections of movement execution. When a combination of feedback types was employed, trace feedback seemed to dominate the impact on execution. Discussion focuses on the contribution of the present study to understanding the impact of specific features inherent to types of real time visual feedback, and the relevance of the present study's result to future research.     

Letters as visual action-effects in skilled typing

In the present study, action-(visual)-effect associations in participants who type using the 10-finger-system and participants who do hunt-and-peck typing were investigated. Following responses (on either a keyboard or an external response device) to colored squares, participants were presented response corresponding or non-corresponding letters. In Experiment 1, evidence for action activation by anticipated action-effects was found. In Experiment 2, evidence that actions can activate the corresponding action-effects was obtained, but only when participants responded on a keyboard and only in the first half of the experimental trials. In both experiments, effects were only present in participants who type using the 10-finger-system. Thus, results provided evidence for bidirectional action-effect associations in 10-finger-system typists. Anticipated visual action-effects are important for action selection in expert typists. Visual action-effects also have a function for performance monitoring, but only in an appropriate context. The functional use of existing action-effect associations is flexible.     

Continuous visual control of interception

People generally try to keep their eyes on a moving target that they intend to catch or hit. In the present study we first examined how important it is to do so. We did this by designing two interception tasks that promote different eye movements. In both tasks it was important to be accurate relative to both the moving target and the static environment. We found that performance was more variable in relation to the structure that was not fixated. This suggests that the resolution of visual information that is gathered during the movement is important for continuously improving predictions about critical aspects of the task, such as anticipating where the target will be at some time in the future. If so, variability in performance should increase if the target briefly disappears from view just before being hit, even if the target moves completely predictably. We demonstrate that it does, indicating that new visual information is used to improve precision throughout the movement.     

Kinematic form and scaling: further investigations on the visual perception of lifted weight

Observers are able to judge accurately the weight lifted by another person when only the motions of reflective patches attached to the lifter's major limb joints and head can be seen (Runeson & Frykholm, 1981). What properties of these complex kinematic patterns allow judgments of weight to be made? The pattern of variation in velocity of the lifted object over position is explored as a source of information for weight: It is found to provide limited information. How are variations in kinematic patterns scaled to allow judgments of weight, a kinetic quantity? The possibility of a source of information for scaling in the kinematics is investigated. Judgments based only on patch-light displays are accurate to a degree that is improved by an extrinsic scaling basis. Finally, the sensitivity to scaling of alternative metrics used in judging is explored. Intrinsic metrics are discovered to be less sensitive to the absence of an extrinsic basis for scaling.     

Brain activity associated with visual awareness

Summaries of recently published papers of interest to cognitive scientists. Readers who would like to contribute to this section, by identifying appropriate papers and writing short summaries, should contact the Editor.     

Endogenous saccades are preceded by shifts of visual attention: evidence from cross-saccadic priming effects

The present study examines whether endogenous saccades are preceded by shifts of attention. Three experiments are reported in which participants were required to execute a saccadic eye movement to a certain location and to subsequently identify the orientation of a target triangle. Prior to the execution of the saccade a prime was presented, which was compatible or incompatible with the target. A priming effect (faster responses in the compatible condition than in the incompatible condition) occurred only when the prime was presented at the saccade destination, and this effect was larger when the prime was presented during oculomotor programming than when it was presented prior to oculomotor programming. The results indicate that an endogenous shift of attention precedes endogenous saccades, providing further support for theories of visual selection that assume a tight coupling between attention and saccades.     

Simultaneous processing of visual information and planning of hand movements in a visuo-manual search task

When searching for a target with eye movements, saccades are planned and initiated while the visual information is still being processed. If hand movements are needed to perform a search task, can they too be planned while visual information from the current position is still being processed? To find out we studied a visual search task in which participants had to move their hand to shift a window through which they could see the items. The task was to find an O in a circle of Cs. The size of the window and the sizes of the gaps in the Cs were varied. Participants made fast, smooth arm movements between items and adjusted their movements, when on the items, to the window size. On many trials the window passed the target and returned, indicating that the next movement had been planned before identifying the item that was in view.     

A consistent failure of the power law for lifted weight

The apparent size of squares was determined as a function of physical area and of surface complexity using the method of magnitude estimation. Apparent area increases as a power function of physical area with a slope of about 0.90. The judged areas also increased as a function of complexity of patterns upon the surface, the most complex surfaces being judged approximately 30% larger than the most simple surfaces.     

Manual pointing to remembered targets...but also in a remembered visual context

In this paper we investigated whether visual background information available during target presentation influences manual pointing to remembered targets. Younger and older participants manually pointed with their unseen hands to remembered or visible targets that were presented or not over a structured visible background. The results indicated that a structured visual background biased movement planning processes, but did not influence motor control processes, regardless of the fact that target location and the background were visible or remembered. How one uses visual background information for movement planning is not modified by aging.     

The potentiation of two components of the reach-to-grasp action during object categorisation in visual memory

Stimulus-Response Compatibility Effects have been reported for several components of the reach-to-grasp action during visual object recognition [Tucker, M., & Ellis, R. (1998). On the relations between seen objects and components of potential actions. Journal of Experimental Psychology: Human Perception and Performance, 24, 830-846; Ellis, R., & Tucker, M. (2000). Micro-affordance: The potentiation of actions by seen objects. British Journal of Psychology, 91, 451-471; Tucker, M., & Ellis, R. (2001). The potentiation of grasp types during visual object categorization. Visual Cognition, 8, 769-800; Creem, S. H., & Proffitt, D. R. (2001). Grasping objects by their handles: A necessary interaction between cognition and action. Journal of Experimental Psychology: Human Perception and Performance, 27, 218-228; Craighero, L. Bello, A. Fadiga, L., & Rizzolatti, G. (2002). Hand action preparation influences the responses to hand pictures. Neuropsychologia, 40, 492-502]. The present study investigates compatibility effects for two elements of reach-to-grasp action during the visual mental imagery of objects-the compatibility of an object for grasping with a power and precision grasp, and the orientation of an object (left/right) for grasping by a particular hand (left/right). Experiment 1 provides further evidence for compatibility effects of a 'seen' object for grasping with a power and precision grasp. The experiment shows that compatibility effects are obtainable when an object is presented in an array of four objects and not just on its own. Experiment 2 provides evidence that compatibility effects of an object for grasping with a power and precision grasp can also be observed when participants make an action response to an object 700 ms after it has been removed from view. Experiment 3 investigates compatibility effects for the orientation of an object for grasping by a particular hand during visual mental imagery, but finds no evidence for such effects. The findings are discussed in relation to two arguments put forward to reconcile ecological and representational theories of visual object recognition.     

Time error in lifted weights as affected by presentation order and judgment mode

In the method of constant stimulus differences, results obtained under two presentation orders (standard first and standard second) are commonly combined to eliminate time error. The present study shows that this technique is not adequate for controlling time error as the presentation orders have differential effects upon PSE. Using a two-handed technique, 96 subjects judged lifted weights on the comparative rating scale. The subjects lifted the standard before, with, or after the variable stimulus. They also either judged the standard in terms of the variable or the variable in terms of the standard (mode of judgment). Judgment mode, a previously uninvestigated confounding variable of presentation order was not an important factor in influencing the value of the PSE.     

Impaired visual perception of hurtful actions in patients with chronic low back pain

Visually presented biological motion stimuli activate regions in the brain that are also related to musculo-skeletal pain. We therefore hypothesized that chronic pain impairs the perception of visually presented actions that involve body parts that hurt. In the first experiment, chronic back pain (CLBP) patients and healthy controls judged the lifted weight from point-light biological motion displays. An actor either lifted an invisible container (5, 10, or 15 kg) from the floor, or lifted and manipulated it from the right to the left. The latter involved twisting of the lower back and would be very painful for CLBP patients. All participants recognized the displayed actions, but CLBP patients were impaired in judging the difference in handled weights, especially for the trunk rotation. The second experiment involved discrimination between forward and backward walking. Here the patients were just as good as the controls, showing that the main result of the first experiment was indeed specific to the sensory aspects of the task, and not to general impairments or attentional deficits. The results thus indicate that the judgment of sensorimotor aspects of a visually displayed movement is specifically affected by chronic low back pain.     

Manipulating response set in a choice reaction task: evidence for anatomical coding in response selection

Accurate motor performance requires a process of response selection that chooses the correct response out of a set of possible ones. Most theories of response selection assume that this selection process operates on spatial codes, which define the location of stimuli and responses in environmental coordinates, with little or no role for the anatomical codes of the effectors involved. In this study, I systematically manipulated the anatomical identities of the response fingers in a four-choice reaction task, while keeping the stimulus and response locations constant. Results showed that homologous fingers on different hands modulated the reaction time profiles and error patterns in a mirror-symmetrical way. This finding indicates that anatomical factors may play a more substantial role in response selection than often assumed.     

Anchor effects in category judgment of weight

Vuorinen, R. Anchor effects in category judgment of weight. Scand. J. Psychol., 1973, 14, 261–272.-3 models of psychophysical judgment are tested in 4 experiments. The anchor effects obtained in these experiments deviate from their usually observed contrast properties violating both the "adaptation-level" (AL) model and the "similarity classification" model. Results on comparative judgment disprove the assumed constancy of the parameters of the AL-model. A comparison with the "response frequency equalization" model discloses that the AL-model confounds genuine perceptual aspects of judgment with response determined factors (response bias) involved in category judgment. The present results are related to a critical evaluation of the general AL-theory presented elsewhere (Vuorinen, 1973).