Attention mechanisms expectancy

Visibility and expectancy. Expectancy, in the context of pedestrian detection, is a psychological variable that represents the degree to which the driver anticipates a pedestrian on the road. To be detected an unexpected object must be conspicuous to attract the drivers fixation (and attention). In contrast, detecting an expected object involves a visual search that is directed at detecting the object s most salient features. If we also know where the object is likely to appear, the process is much quicker because our visual fixation and attentional mechanisms are already directed at it (see Chapters 3 and 4 for a discussion on the difference between top-down and bottom-up processing and visual attention, respectively). Several studies have demonstrated the importance of expectancy for pedestrian detection. The effect was first quantified nearly three quarters of a century ago by Roper and Howard (1938), who measured driver s detection distance to an obstacle on the road when it was either expected or unexpected. With 46 drivers/observers they found that "the average driver perceives the unexpected obstacle only half as far away as from the expected one...all of them saw the unexpected obstacle at least 20 percent as far as the expected obstacle, whereas none saw it at more than 80 percent of the distance." (pp. 419-420). Thus, this seminal study showed that an imexpected pedestrian is likely to be detected at half the distance as an expected one. 

One should note overall, that while some of these suggested mechanisms may in the future prove to have a role in the control of smooth muscle contraction, in chemically skinned preparations maximum force development follows activation by the MLCK active subunit in extremely low Ca " ion concentrations. The conclusion can hardly be avoided that phosphorylation alone is sufficient for activation, and if another mechanism is involved, it is not necessary for the initial genesis of force. If such mechanisms are operative, then they might be expected to run in parallel or consequent to myosin phosphorylation. A possible example of this category of effect is that a GTP-dependent process (G-protein) shifts the force vs. Ca ion concentration relationship to lower Ca ion concentrations. This kind of mechanism calls attention to the divergence of signals along the intracellular control pathways. 

Indeed, whenever you focus your attention on any of the so-called intelligent systems, and you take the time to leam the mechanisms they use to generate their marvelous and wondrous behavior, you come up with the anti-climactic realization that everything is quite ordinary and perfectly expectable with no surprises or mystical insights. Such reaction reminds us of how Sherlock Holmes reacted when a man questioned the brilliance of his deductive reasoning in solving one of his cases ... 

In recent years attention has focused on the role of intrinsic binding energy and entropic factors as major contributors to enzyme catalytic efficiency (Page and Jencks, 197l Jencks, 1975,1981). The ribonuclease mechanism conforms to expectations based on these ideas. In particular, distortion occurs to raise the ground state of the substrate in the S complex, and the bound substrate interacts with the enzyme in a manner such that the enzyme becomes complementary to the transition state of the reaction during the catalytic cycle. 

Plastics. Part of the trend to substitute plastic and composite substrates for metals can be attributed to a desire to avoid the process of metallic corrosion and subsequent failure. Relatively little attention has been called to the possible failure modes of plastics under environments considered corrosive to metals. More extensive work should be conducted on the durability and life expectancy of plastic and composite materials under end-use environments. A further consideration is the potential for polymer degradation by the products of metal corrosion in hybrid structures comprising metal and polymer components. Since it is expected that coatings will continue to be used to protect plastic and composite substrates, ancillary programs need to be conducted on the mechanisms by which coatings can protect such substrates. 

Because of these rapid removal processes in the troposphere, the contribution of iodine to stratospheric photochemistry has not received much attention. However, Solomon et al. (1994) suggested that rapid transport from the lower troposphere into the upper troposphere and lower stratosphere via convective clouds could provide a mechanism for injecting such compounds into the stratosphere. While the relevant chemistry of iodine is not well known, it would be expected to interact with the CIO cycles in much the same way as BrO, e.g.,... 

Studies on artificial ion channels are expected to provide important information on molecular mechanisms and to deepen our understanding of natural ion channels through the establishment of a detailed structure-function relationship. At the same time, the research will contribute to the fascinating area of nanoscale transducers, and may eventually lead to the development of so-called molecular ionics. Here, the author would like to describe the basic concept for the molecular design of various artificial ion channels and to compare their characteristics in the hope of stimulating a future explosion of this research field. Special attention is focused on non-peptidic approaches. Helical bundle approaches " and studies on modified antibiotics " are beyond the scope of this review. 

Although the uniaxial test has traditionally received the most attention, such tests alone may be insufficient to characterize adequately the mechanical capability of solid propellants. This is especially true for ultimate property determinations where a change in load application from one axis to several at once may strongly affect the relative ranking of propellants according to their breaking strains. Since the conditions usually encountered in solid rocket motors lead to the development of multiaxial stress fields, tests which attempt to simulate these stress fields may be expected to represent more closely the true capability of the material. 

There are many arguments for the rational-expectations hypothesis. In the simple cobweb cycle, and even with adaptive expectations, we must assume that each agent believes himself to be the only one to adjust rationally to the circumstances and that others act in a more or less mechanical way But this is an irrational belief, which we should not impute to people without evidence. It is surely more plausible to assume that people believe others to be as rational as themselves. Also, in a rapidly changing world people would be silly to pay much attention to the past. When oil prices quadrupled in 1973, the prices of oil before 1973 lost all relevance as guides to future prices. And if ordinary people understood much less of the economy than economists do, we would expect the latter to make much more money than they in fact do. The reason economists don t make a killing by outguessing the market is that the market has access to whatever information they have and can use it just as efficiently. ... 

---