14 research outputs found
Visual target distance, but not visual cursor path length produces shifts in motor behavior: a multisensory integration perspective
No full textvan Dam L. Visual target distance, but not visual cursor path length produces shifts in motor behavior: a multisensory integration perspective. Frontiers in Psychology. 2014;5:650
Bi-stability in perceived slant when binocular disparity and monocular perspective specify different slants
No full textvan Ee R, van Dam L, Erkelens CJ. Bi-stability in perceived slant when binocular disparity and monocular perspective specify different slants. JOURNAL OF VISION. 2002;2(9): 2
Voluntary control and the dynamics of perceptual bi-stability
No full textvan Ee R, van Dam L, Brouwer GJ. Voluntary control and the dynamics of perceptual bi-stability. VISION RESEARCH. 2005;45(1):41-55
Switching between visuomotor mappings: learning absolute mappings or relative shifts?
No full textvan Dam L, Hawellek DJ, Ernst MO. Switching between visuomotor mappings: learning absolute mappings or relative shifts? Perception. 2008;37(Suppl. 1):109
Preexposure disrupts learning of location-contingent perceptual biases for ambiguous stimuli
No full textvan Dam L, Ernst MO. Preexposure disrupts learning of location-contingent perceptual biases for ambiguous stimuli. Journal of Vision. 2010;10(8):15-15
Modeling Multisensory Integration
No full textThe different senses, such as vision, touch, or audition, often provide redundant information for perceiving our environment. For instance, the size of an object can be determined by both sight and touch. In this chapter, Loes C.J. van Dam, Cesare V Parise, and Marc Ernst discuss the statistical optimal framework for combining redundant sensory information to maximize perceptual precision ? the Maximum Likelihood Estimation (MLE) framework ? and provides examples on how human performance approaches optimality. In the MLE framework, each cue is weighed according to its precision, that is, the more precise sensory estimate receives a higher weight when integration occurs. However, before integrating multisensory information, the perceptual system needs to determine whether or not the sensory signals correspond to the same object or event (the so-called correspondence problem). Current ideas on how the perceptual system solves the correspondence problem are provided in the same mathematical framework. Additionally, the chapter briefly reviews learning and developmental influences on multisensory integration
Knowing Each Random Error of Our Ways, but Hardly Correcting for It: an Instance of Optimal Performance
No full textvan Dam L, Ernst MO. Knowing Each Random Error of Our Ways, but Hardly Correcting for It: an Instance of Optimal Performance. PLOS ONE. 2013;8(10): e78757.Random errors are omnipresent in sensorimotor tasks due to perceptual and motor noise. The question is, are humans aware of their random errors on an instance-by-instance basis? The appealing answer would be ‘no’ because it seems intuitive that humans would otherwise immediately correct for the errors online, thereby increasing sensorimotor precision. However, here we show the opposite. Participants pointed to visual targets with varying degree of feedback. After movement completion participants indicated whether they believed they landed left or right of target. Surprisingly, participants' left/right-discriminability was well above chance, even without visual feedback. Only when forced to correct for the error after movement completion did participants loose knowledge about the remaining error, indicating that random errors can only be accessed offline. When correcting, participants applied the optimal correction gain, a weighting factor between perceptual and motor noise, minimizing end-point variance. Together these results show that humans optimally combine direct information about sensorimotor noise in the system (the current random error), with indirect knowledge about the variance of the perceptual and motor noise distributions. Yet, they only appear to do so offline after movement completion, not while the movement is still in progress, suggesting that during movement proprioceptive information is less precise
Retinal image shifts, but not eye movements per se, cause alternations in awareness during binocular rivalry.
No full textParticularly promising studies on visual awareness exploit a generally used perceptual bistability phenomenon, "binocular rivalry"--in which the two eyes' images alternately dominate--because it can dissociate the visual input from the perceptual output. To successfully study awareness, it is crucial to know the extent to which eye movements alter the input. Although there is convincing evidence that perceptual alternations can occur without eye movements, the literature on their exact role is mixed. Moreover, recent work has demonstrated that eye movements, first, correlate positively with perceptual alternations in binocular rivalry, and second, often accompany covert attention shifts (that were previously thought to be purely mental). Here, we asked whether eye movements cause perceptual alternations, and if so, whether it is either the execution of the eye movement or the resulting retinal image change that causes the alternation. Subjects viewed repetitive line patterns, enabling a distinction of saccades that did produce foveal image changes from those that did not. Subjects reported binocular rivalry alternations. We found that, although a saccade is not essential to initiate percept changes, the foveal image change resulting from a (micro)saccade is a deciding factor for percept dominance. We conclude that the foveal image must change to have a saccade cause a change in awareness. This sheds new light on the interaction between spatial attention shifts and perceptual alternations
Depth constancy and the absolute vergence anomaly
No full textBinocular disparity provides information about the depth structure of objects and surfaces in
our environment. Since disparity depends on the distance to objects as well as the depth
separation of points, information about distance is required to estimate depth from disparity.
Our perception of size and shape is biased, such that far objects appear too small and
flattened in depth, and near objects too big and stretched in depth. The current study
assessed the extent to which the failure of depth constancy can be accounted for by the
uncertainty of distance information provided by vergence. We measured individual
differences in vergence noise using a nonius line task, and the degree of depth constancy
using a task in which observers judged the magnitude of a depth interval relative to the
vertical distance between two targets in the image plane. We found no correlation between
the two measures, and show that depth constancy was much poorer than would be expected
from vergence noise measured in this way. This limited ability to take account of vergence in
the perception of depth is, however, consistent with our poor sensitivity to absolute disparity
differences. This absolute disparity anomaly thus also applies to our poor ability to make use
of vergence information for absolute distance judgements
Bayesian Modeling of Perceiving: A Guide to Basic Principles
No full textPhilosophical reflection on perceptual consciousness has typically adopted a modality-specific perspective as its point of departure. According to this approach, an account of perceptual consciousness as a whole will simply fall out of an account of each of the various perceptual modalities. In this chapter, Tim Baynes argues against one manifestation of this atomistic approach to perceptual experience: the decomposition thesis. According to the decomposition thesis, a person?s overall perceptual experience can be identified with the sum of their modality-specific experiences. He examines objections to the decomposition thesis deriving from three sources: the phenomenal unity of consciousness, the existence of common sensibles, and the nature of multisensory integration, focusing in most detail on the last of these three objections
