Halo effects

Convergence. The tendency of a test sample, regardless of quaUty, to be perceived as similar to prior sample(s) sometimes called the halo effect. 

Central nervous system-headache, apathy, drowsiness, visual disturbances (blurred vision, disturbance in yellow/green vision, halo effect around dark objects), mental depression, confusion, disorientation, delirium... 

Observational bias by halo effects. Perception of an ADR may be swamped by the symptoms of the disease, thus as the disease symptoms resolve the ADR becomes apparent. 

The placebo is useful in (a) distinguishing the pharmacod)mamic effects of a drug from the psychological impact of the medication and the environment in which it is given (the "halo" effect of the enthusiastic, or pessimistic, research clinician). It is well known, for example, that the placebo effect in major depression is as high as 30% while that of an effective antidepressant is approximately 60% of the optimal response. This statistic illustrates the importance of placebo-based studies in evaluating the efficacy of a new psychotropic drug. 

Rather than requiring the rater to evaluate employees on a predetermined set of characteristics or standards, relative systems require the manager to make comparisons among employees. Relative systems have an advantage over absolute systems in that central tendency and leniency effects are minimized. The likelihood of the halo effect occurring is also reduced. The fact that employees are pitted against one another, so to speak, makes it easier to base organizational rewards on merit. 

Three types of relative performance appraisal systems are used. One is called alternation ranking, a method in which the rater chooses the most and least valuable persons from a list of employees with similar jobs. Both names are crossed off, and then the procedure is repeated until every employee on the list has been ranked. With its ability to eliminate central tendency and leniency and with its ease of implementation, alternation ranking may appear appealing. However, aside from its failure to generate feedback, the halo effect could come into play. Moreover, employees may be concerned with the potential for bias and inaccuracy by the evaluator, especially when criteria for performance have not been delineated clearly. 

We still have not, as a country, decided whether health care is a social service, says Paul Reitemeier, the health care ethicist. If it were, we would guarantee access to it, as we do education and food stamps. Okay then, so the public considers the drug industry a business. But that s not quite true either. Consumers lose sight of the fact that the pharmaceutical industry is proprietary, not altruistic. They re [drug companies] not in the health care business they re in the business of providing tools. But because it s health care, they get the halo effect. ... 

Figure 21. White-light (top) and blue-light fluorescence mode (bottom) photomicrographs of a water-in-oil emulsion. With white light the water droplets have internal reactions that lead to a halo effect and an incorrect size estimate. With incident blue—violet light to excite oil-phase fluorescence, the emulsified water droplets appear as dark circles in a bright oil background and are significantly easier to size. However, droplets that are above or below the plane of focus will still be incorrectly sized.

In a communication on Doblin s discovery of statistical error, Metzner (1998) wrote We fell victims to the well-known halo effect, by which researchers tend to see their data in as positive a light as possible. He suggested the mistakes made were unconscious mistakes of overenthusiasm, rather than deliberate faking, if only for the reason that our own results clearly show the inconsistencies. ... 

Mechanochemical treatment of VPBiO sample (Dl) suspended in water and in the absence of any dispersant did not lead to important changes in phase composition. During the catalyst treatment in ethanol in the presence of hydrazine some visible changes occurred in its XRD pattern. Thus, for the sample treated for 40 min (D1-M40) the weak peaks at d = 0.386 and 0.313 nm attributed to the (VO)2P207 phase appear against a significant halo-effect. The... 

In the present paper, impregnated IPV samples on aerosil, containing 5, 10 and IS wt.% vanadium at fp of about 0.6 were prepared. AU the XRD patterns for the samples are proved to be very similar and contain the most characteristic reflections of P-VOPO4, a-V0P04 and (V0)2P207 phases against the considerable halo-effect. 

Hence, the total appearance of a particular food conununicates in a number of ways. First, it tells us about the food itself and second, through a halo effect, about the properties of other foods. 

Colour and appearance are powerful indicators of object quality. This applies particularly to food. Human beings have different sensitivities to flavour and it is relatively easy to confuse tasters by giving them inappropriately coloured foods (Moir 1936). The existence of the halo effect results in some foods having to be tailored for a particular market. For example, the French prefer their rose wines to... 

Halo effects arise from a number of sources during sensory testing (Hutchings... 

As a result, amorphous materials exhibit the classical diffuse halo x-ray powder diffraction pattern rather than the sharp peaks observed in the pattern of a crystalline substance. When the halo is broad, it is often difficult to distinguish between a material that is truly amorphous (e.g., a true glass) and one that is merely microcrystalline. This situation exists because when microcrystallites have diameters less than about 50 A in diameter, a similar halo effect is observed. 

Another system for examination of low-contrast objects such as living cells is the Nomarski or differential interference contrast system. It is also particularly useful for materials that cannot be stained satisfactorily for other reasons, such as very thin sections that take up too little stain. This system employs polarizing filters and quartz prisms instead of the annular diaphragm and phase plates used in phase contrast. This eliminates the halo effect seen in phase contrast, rendering sharply defined images with good contrast, having a characteristically (pseudo) three-dimensional appearance. It is rather less suited to routine work than phase contrast however, and is considerably more expensive. 

Halo effect (ca. 1928) n. Piling up of ink at the edges of printed letters and dots. Also colored or sometimes uncolored areas adjacent to them, caused by the spread of colored or uncolored vehicles. Leach RH, Pierce RJ, Hickman EP, Mackenzie MJ, Smith HG (eds) (1993) Printing ink manual, 5th edn. Blueprint, New York. 

Osmium metal and most of its compounds are probably safe to handle with proper precautions, but OSO4 and OsFg are highly toxic. The compound OSO4 is a hazard to the eyes, nose, and throat and readily oxidizes organic matter. It can cause dermatitis and ulceration of the skin on contact, as well as cause conjunctivitis, corneal irritation, halo effects, and temporary blindness. 

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