2,263 research outputs found
The role of attention in motion extrapolation: Are moving objects 'corrected' or flashed objects attentionally delayed?
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The Illusion of the Perpetual Money Machine
We argue that the present crisis and stalling economy continuing since 2007
are rooted in the delusionary belief in policies based on a "perpetual money
machine" type of thinking. We document strong evidence that, since the early
1980s, consumption has been increasingly funded by smaller savings, booming
financial profits, wealth extracted from house price appreciation and explosive
debt. This is in stark contrast with the productivity-fueled growth that was
seen in the 1950s and 1960s. This transition, starting in the early 1980s, was
further supported by a climate of deregulation and a massive growth in
financial derivatives designed to spread and diversify the risks globally. The
result has been a succession of bubbles and crashes, including the worldwide
stock market bubble and great crash of October 1987, the savings and loans
crisis of the 1980s, the burst in 1991 of the enormous Japanese real estate and
stock market bubbles, the emerging markets bubbles and crashes in 1994 and
1997, the LTCM crisis of 1998, the dotcom bubble bursting in 2000, the recent
house price bubbles, the financialization bubble via special investment
vehicles, the stock market bubble, the commodity and oil bubbles and the debt
bubbles, all developing jointly and feeding on each other. Rather than still
hoping that real wealth will come out of money creation, we need fundamentally
new ways of thinking. In uncertain times, it is essential, more than ever, to
think in scenarios: what can happen in the future, and, what would be the
effect on your wealth and capital? How can you protect against adverse
scenarios? We thus end by examining the question "what can we do?" from the
macro level, discussing the fundamental issue of incentives and of constructing
and predicting scenarios as well as developing investment insights.Comment: 27 pages, 18 figures (Notenstein Academy White Paper Series
Estimating the subjective perception of object size and position through brain imaging and psychophysics
Perception is subjective and context-dependent. Size and position perception are no exceptions. Studies have shown that apparent object size is represented by the retinotopic location of peak response in V1. Such representation is likely supported by a combination of V1 architecture and top-down driven retinotopic reorganisation. Are apparent object size and position encoded via a common mechanism? Using functional magnetic resonance imaging and a model-based reconstruction technique, the first part of this thesis sets out to test if retinotopic encoding of size percepts can be generalised to apparent position representation and whether neural signatures could be used to predict an individual’s perceptual experience. Here, I present evidence that static apparent position – induced by a dot-variant Muller-Lyer illusion – is represented retinotopically in V1. However, there is mixed evidence for retinotopic representation of motion-induced position shifts (e.g. curveball illusion) in early visual areas. My findings could be reconciled by assuming dual representation of veridical and percept-based information in early visual areas, which is consistent with the larger framework of predictive coding. The second part of the thesis sets out to compare different psychophysical methods for measuring size perception in the Ebbinghaus illusion. Consistent with the idea that psychophysical methods are not equally susceptible to cognitive factors, my experiments reveal a consistent discrepancy in illusion magnitude estimates between a traditional forced choice (2AFC) task and a novel perceptual matching (PM) task – a variant of a comparison-of-comparisons (CoC) task, a design widely seen as the gold standard in psychophysics. Further investigation reveals the difference was not driven by greater 2AFC susceptibility to cognitive factors, but a tendency for PM to skew illusion magnitude estimates towards the underlying stimulus distribution. I show that this dependency can be largely corrected using adaptive stimulus sampling
Do the flash-lag effect and representational momentum involve similar extrapolations?
In the flash-lag effect (FLE) and in representational momentum (RM), the represented position of a moving target is displaced in the direction of motion. Effects of numerous variables on the FLE and on RM are briefly considered. In many cases, variables appear to have the same effect on the FLE and on RM, and this is consistent with a hypothesis that displacements in the FLE and in RM result from overlapping or similar mechanisms. In other cases, variables initially appear to have different effects on the FLE and on RM, but accounts reconciling those apparent differences with a hypothesis of overlapping or similar mechanisms are suggested. Given that RM is simpler and accounts for a wider range of findings (i.e., RM involves a single stimulus rather than the relationship between two stimuli, RM accounts for displacement in absolute position of a single stimulus and for differences in relative position of two stimuli), it is suggested that (at least some cases of) the FLE might be a special case of RM in which the position of the target is assessed relative to the position of another stimulus (i.e., the flashed object) rather than relative to the actual position of the target
Position representations of moving objects align with real-time position in the early visual response
When interacting with the dynamic world, the brain receives outdated sensory information, due to the time required for neural transmission and processing. In motion perception, the brain may overcome these fundamental delays through predictively encoding the position of moving objects using information from their past trajectories. In the present study, we evaluated this proposition using multivariate analysis of high temporal resolution electroencephalographic data. We tracked neural position representations of moving objects at different stages of visual processing, relative to the real-time position of the object. During early stimulus-evoked activity, position representations of moving objects were activated substantially earlier than the equivalent activity evoked by unpredictable flashes, aligning the earliest representations of moving stimuli with their real-time positions. These findings indicate that the predictability of straight trajectories enables full compensation for the neural delays accumulated early in stimulus processing, but that delays still accumulate across later stages of cortical processing
Mental and sensorimotor extrapolation fare better than motion extrapolation in the offset condition
Evidence for motion extrapolation at motion offset is scarce. In contrast, there is abundant evidence that subjects mentally extrapolate the future trajectory of weak motion signals at motion offset. Further, pointing movements overshoot at motion offset. We believe that mental and sensorimotor extrapolation is sufficient to solve the problem of perceptual latencies. Both present the advantage of being much more flexible than motion extrapolatio
Use your illusion: the flash-lag effect as a tool for psychophysics
The flash-lag effect is an illusion in which a moving object is perceived advanced
beyond an aligned flash. The majority of research into the effect has been directed at
specifying its source, though a small body of literature simply makes use of flash-lag to
answer diverse questions about perception – without necessarily arbitrating between
competing accounts of its nature. The current thesis expands on this little-explored
potential of the flash-lag effect with the presentation of three papers reporting
programmes of research that exploit the phenomenon to address issues unrelated to its
cause. In the first paper it is shown that, like in visual flash-lag, a similar motion
direction based anisotropy is evident in the motor version of the effect, in which one’s
unseen limb is perceived ahead of a flash. Specifically, the effect is greater for motion
towards, rather than away from fixation. Furthermore, Paper I also demonstrates for the
first time a motor flash-drag effect, in which one’s unseen moving hand ‘drags’ the
perceived position of a nearby flash. It is argued that both of these findings are evidence
of parallels between vision and action systems. Paper II takes advantage of the
explicitly perceptual nature of the flash-lag effect to investigate whether the visuospatial
perception of threatening objects is different to that of non-threatening objects. It is
ultimately shown that when a moving stimulus is threatening, the flash-lag effect is
greater, regardless of its direction of motion. Paper III shows that gamma movement
(the apparent contraction of disappearing stimuli) adds to and subtracts from the
forward displacement of contracting and expanding stimuli, respectively. Prior to these
papers, however, an overview chapter reviews the flash-lag literature, and argues that
the effect can be a useful tool for psychophysics, even without a consensus on its origin
Exploring the Visual-Tactile Temporal Binding Window and Multisensory Influences on Sensorimotor Synchronization
Meaningful interaction with our environment relies upon timely integration of multisensory information and actions performed in synchrony with sensory input. This thesis examines the temporal binding window for visual-tactile integration using the simultaneity judgement task, and the influence of multisensory information on sensorimotor synchronization. Additionally, this thesis investigates functional connectivity between unisensory and multisensory neural regions during, and immediately following stimulus presentation, in the simultaneity judgement task to understand differences between simultaneous and non-simultaneous perceptio
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