Learning by trial and error

Psychostimulants have produced inconsistent effects on tests of cognition. Several studies have investigated the effect of cocaine on a test of repeated acquisition and performance of response sequences. In the acquisition component, subjects attempt to learn by trial and error a predetermined sequence of 10 numbers within 20 trials. Subjects learn a new sequence each time they perform the test. In the performance component, the response sequence remains constant throughout the experiment, and thus subjects repeat an already learned sequence. Two studies have reported no effect of either intranasal (IN) or IV cocaine on the test.37 40 However, Higgins et al.51 reported that cocaine (96 mg, IN) decreased response rate during the acquisition phase and increased response accuracy during the performance component. In a similar serial acquisition procedure, cocaine has been shown to have no effect.52 53... 

According to present views, the rat, driven by fear, tries to prevent punishment and learns by trial and error to escape in due time. The efficiency of learning is thought to be proportional to the number of the successful crossings in response to flash light within 10 s. According to our new concept the... 

When an organic solvent is to be used, one should be mindful that the best solvent will depend on the over-all characteristics of the system under study and usually the specific solvent properties needed for a particular application can best be learned by trial and error. 

Every solution to a wicked problem is a one-shot operation because there is no opportunity to learn by trial and error every attempt counts significantly. 

But even with the necessary molds on hand, casting HE was far from simple, another technology that had to be learned by trial and error. In February 1945 Kistiakowsky chose an explosive called Composition B to serve as the fast-buming component of Fat Man s lenses and a mixture he had commissioned from a Navy research laboratory, Baratol, for the slow-burning component. Composition B was poured as a hot slurry of wax, molten TNT and a non-melting crystalline powder, RDX, that was 40 percent more powerful than TNT alone. Baratol slurried barium nitrate and aluminum powder with TNT, stearoxyacetic acid and nitrocellulose ... 

From the earliest times chemicals have been used in the treatment of disease. The substances that were first used as drugs are natural products such as in the leaves, branches, and roots of plants. Man (perhaps more often women than men) slowly learned by trial and error that the ingestion of certain plants had certain effects. It was discovered, for example, that ingestion of certain plants of the family Solanaceae causes mydriasis, the dilation of the pupil of the eye. One of these plants is named//opr/ belladonna. Belladonna means beautiful woman and it was, and perhaps still is, thought that women with large pupils are more beautiful than those with small pupils. 

This goes to show that everyone has a different way of solving problems. We all learn by trial and error. Sometimes we get things to work right the first time other times we do not. We must always strive for the best, always look for proven methods, and avoid reinventing the wheel. The management system must always be adaptable to enable continuous improvement. Any company that institutes a cultural change toward the zero-incidents concept is bound to see safety improvements that the entire workforce can be proud of. 

Electric gas monitors have been around for decades, and became mass produced and gained popularity in the 1970s. When gas monitors were sold, typically the only way a user could learn how to use it would be to read an owner s manual and then learn by trial and error in the field. The equipment was generally light on features, heavy in size and weight, and umeliable. Operators would have to learn idiosyncrasies about the devices on their own or through the experiences of others and by word-of-mouth. While this was not the safest way to approach the use of a gas detector, in some small way, social learning in gas detection was bom. 

American troops did not see Japanese flame throwing vehicles until they captured eight on Luzon in 1945. The weapons were placed on amphibious tractors, similar to American DUKW s. The Japanese did not have fuel thickeners comparable to American napalm, and had to use mixtures of crude oil, gasoline, and kerosene. Since Japanese troops employed portable flame throwers against Americans from early 1942 onward, it is difficult to explain why they did not use mechanized flame throwers. American troops learned by trial and error of the value of flame tanks, and perhaps the Japanese never threw off their conservatism sufficiently to give the tanks full-scale battle tests. ... 

Only natural dyes were known until the nineteenth century. By trial and error and probably also by chance, humans learned to extract and use a large variety of dyes of vegetable and animal origin. Dyes were extracted from the roots, trunk bark, and branches of trees, the stems, leaves, flowers, and fruits of plants, the bodies of insects and mollusks, and the eggs of insects. All the dyes obtained from natural sources are rather impure, and hence the accurate reproducibility of colors was almost impossible during antiquity. Still, many of the dyes and dyeing techniques used in antiquity were highly developed and remained in use until the discovery of the synthetic dyes in the middle of the nineteenth century (Colombo 1995 Robinson 1969). 

While much has been learned about the role and selection of the operation parameters in displacement chrcmatography (60-66), little is known yet about the rules of displacer selection and the means available to control the selectivity of the separation. The paucity of well characterized displacers and the lack of knowledge of the solute adsorption isotherms hinder most strongly the wider acceptance and use of displacement chromatography. In most cases, displacer selection is still done by trial-and-error. In the majority of modem displacement chromatographic publications a reversed-phase system was used to separate small polar molecules, antibiotics, oligopeptides and small proteins (52-66). 

Research in this discipline is important because of the potential to accelerate the materials development for sensors by applying what has already been learned in other fields, such as electronics, aerospace, and biomaterials. By combining an understanding of sensor issues with a broad understanding of how polymer problems have been solved in other fields, polymer development for specific sensor applications will advance more rapidly. The logical progression from materials development by trial and error is to tailor new materials systematically for each specific application, based on understanding of material science. 

Formulating skills cannot be easily learned in the classroom or from reading books. These sources can provide a starting point and a road map, but that is not the end point. Formulating is somewhat of an art and as such can only be effectively learned at the bench by practicing and, unfortunately, often by trial and error. This book can be a means of reducing the time, cost, and potential problems inherent in this process. 

By trial and error over the centuries, man has learned five basic skills in handling oilseeds ... 

Sometimes the relative numbers of moles you get when you calculate an empirical formula will not turn out to be whole numbers, as is the case in Example 6.11. When this happens, you must convert to the appropriate whole numbers. This is done by multiplying all the numbers by the same smallest whole number, which can be found by trial and error. The multiplier needed is almost always between 1 and 6. We will now summarize what we have learned about calculating empirical formulas. 

Another way to establish a cooperative outcome is through evolutionary analysis. In this view, players are myopic they form their strategies one stage at a time and learn from thdr past experience. Cooperation does not emerge instantaneously but over time, as players adjust thdr strategies by trial and error. For a fascinating and deservedly influential account of this approach, see Axelrod (1984). 

The history of the world fertilizer industry can be traced to the e2irliest agriculture when man began cultivation of plants to produce food. Prior to cultivation of plants and domestication of animals, man was a hunter and. gatherer of whatever sources of food he could find in his local environment. The early farmers soon learned that some soils were more productive than others they also learned that continuous cultivation of the same land resulted in reduced yields. Some learned that the addition of manures, composts, fish, ashes, and other substances would sometimes increase yields or apparently restore productivity to fields that were considered to be "worn out. Most of these soil amendments (the first fertilizers) were discovered by trial and error, and results were unpredictable. 

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