Showing papers by "University of British Columbia published in 1979"

Prospect theory: an analysis of decision under risk

Abstract: This paper presents a critique of expected utility theory as a descriptive model of decision making under risk, and develops an alternative model, called prospect theory. Choices among risky prospects exhibit several pervasive effects that are inconsistent with the basic tenets of utility theory. In particular, people underweight outcomes that are merely probable in comparison with outcomes that are obtained with certainty. This tendency, called the certainty effect, contributes to risk aversion in choices involving sure gains and to risk seeking in choices involving sure losses. In addition, people generally discard components that are shared by all prospects under consideration. This tendency, called the isolation effect, leads to inconsistent preferences when the same choice is presented in different forms. An alternative theory of choice is developed, in which value is assigned to gains and losses rather than to final assets and in which probabilities are replaced by decision weights. The value function is normally concave for gains, commonly convex for losses, and is generally steeper for losses than for gains. Decision weights are generally lower than the corresponding probabilities, except in the range of low prob- abilities. Overweighting of low probabilities may contribute to the attractiveness of both insurance and gambling. EXPECTED UTILITY THEORY has dominated the analysis of decision making under risk. It has been generally accepted as a normative model of rational choice (24), and widely applied as a descriptive model of economic behavior, e.g. (15, 4). Thus, it is assumed that all reasonable people would wish to obey the axioms of the theory (47, 36), and that most people actually do, most of the time. The present paper describes several classes of choice problems in which preferences systematically violate the axioms of expected utility theory. In the light of these observations we argue that utility theory, as it is commonly interpreted and applied, is not an adequate descriptive model and we propose an alternative account of choice under risk. 2. CRITIQUE

Affective space is bipolar.

Abstract: Numerous previous studies found monopolar rather than bipolar dimensions of affect (defined as emotion represented in language), but may have included methodological biases against bipolarity. The present study of self-report data (N = 150) on 11 affect scales showed that response format and acquiescence response style significantly shifted correlations between hypothesized opposites away from showing bipolarity. When these biases were taken into account, pleasure was found to be the bipolar opposite of displeasure and arousal of sleepiness. In turn, pleasure-displeasure and degree of arousal formed a twodimensional bipolar space that accounted for almost all of the reliable variance in Thayer's four factors of activation plus a measure of depression. Dominance and submissiveness factors were also included in the study, but invalidity of the scales used precluded any conclusions regarding their bipolarity.

A continuous time approach to the pricing of bonds

Abstract: This paper develops an arbitrage model of the term structure of interest rates based on the assumptions that the whole term structure at any point in time may be expressed as a function of the yields on the longest and shortest maturity default free instruments and that these two yields follow a Gauss-Wiener process. Arbitrage arguments are used to derive a partial differential equation which must be satisfied by the values of all default free bonds. The joint stochastic process for the two yields is estimated using Canadian data and the model is used to price a sample of Government of Canada bonds.

The biology of heterostyly

Abstract: Heterostyly is a genetically controlled floral polymorphism that is known to occur in 24 families of flowering plants. The floral morphs differ reciprocally in stamen and style lengths. They often differ in pollen grain size and production, and may differ in pollen exine sculpturing, pollen colour, presence of starch in pollen, stigmatic papillae, or corolla size or morphology. There are two morphs in distylous plants and three morphs in tristylous plants. Distyly is much more common than tristyly. Tristyly is known to occur only in the Lythraceae, Oxalidaceae, and Pontederiaceae, although there are unconfirmed reports in the Connaraceae and in Hugonia of the Linaceae. In distylous plants the supergene determining floral morphology also controls a diallelic sporophytic self-incompatibility system, so that only pollinations between morphs are compatible. Tristylous plants usually possess a two-locus diallelic sporophytic self-incompati-bility system associated with the floral trimorphism, but whet...

Management of multispecies fisheries.

Abstract: With the overexploitation of many conventional fish stcocks, and growing interest in harvesting new kinds of food from the sea, there is increasing need for managers of fisheries to take account of interactions among species. In particular, as Antarctic krill-fishing industries grow, there is a need to agree upon sound principles for managing the Southern Ocean ecosystem. Using simple models, we discuss the way multispecies food webs respond to the harvesting of species at differrent trophic levels. These biological and economic insights are applied to a discussion of fisheries in the Southern Otean and the North Sea and to enunciate some for harvesting in multispecies systems.

Utility Theory: Axioms Versus ‘Paradoxes’

Abstract: Few attempts have yet been made to interrelate the major axiom systems of expected utility theory such as those presented by von Neumann—Morgenstern, Marschak, Savage, and Arrow. This paper attempts to consolidate the theoretical and empirical research on these axioms by showing the correspondences among the major axioms of each system and highlighting their similarities and differences in dealing with concepts such as probability and utility.

Toward a Clearer Definition of the Attentional Deficit of Hyperactive Children

Abstract: Over the past several years, acceptance of the central importance of an attentional deficit in hyperactive children has been emerging in the clinical, educational, and research literature. When we examine the definitions of attentional deficit being used by different authors, however, it becomes evident that a good deal of confusion and disagreement remains about the exact nature of the deficit being attributed to hyperactive children.

Sensation and perception

Abstract: Preface. Sensation and Perception. Measuring Perception. Brightness & Color. The Auditory System. Hearing. Taste, Smell, Touch, and Pain. Patterns and Edges. Space. Objects and Scenes. Time. Motion. Attention. Consciousness. Development. Learning and Experience. References. Index.

Regional topography within noradrenergic locus coeruleus as revealed by retrograde transport of horseradish peroxidase

Abstract: A hitherto unsuspected degree of regional topographic organization in the noradrenergic nucleus, locus coeruleus, was revealed by the use of retrograde transport of horseradish peroxidase (HRP) from terminal areas receiving noradrenergic innervation. HRP was injected into hippocampus, hypothalamus, thalamus, caudate-putamen, septum, amygdala-piriform cortex, cerebellum and cortex. Successful transport was obtained from all areas, including the caudate-putamen and cerebral cortex. The pattern of HRP positive cells in the ipsilateral locus coeruleus was markedly different depending on the location of the HRP injection. Thus, hippocampal injections labeled cells in the dorsal locus coeruleus but not at all in the ventral tip. Injections of HRP into caudate-putamen or cerebellum labeled the ventral tip along with the rest of the dorsal portion. HRP injections into the septum labeled cells only in the dorsal half of the dorsal locus coeruleus. There thus exists a three tier division of locus coeruleus into the ventral one third, dorsal one third and intermediate one third. A further division was seen in the anterior-posterior plane with HRP injections into the thalamus labeling the posterior pole of locus very intensely but with little transport to more anterior levels; conversely HRP injection into the hypothalamus resulted in intense labeling only in the anterior pole of locus coeruleus. Amygdala-piriform cortex HRP injections revealed a further pattern with very intensely reactive cells scattered sparsely throughout the nucleus. Cortical HRP injections yielded weaker labeling also in occasional, scattered cells. All HRP transport to locus coeruleus was shown to be noradrenergic by degeneration with 6-hydroxydopamine and due to terminal, rather than fiber of passage, uptake by control injection into the dorsal NA bundle. It is concluded that the locus coeruleus is not an homogenous nucleus with respect to the origin of the noradrenergic projections to sundry forebrain, spinal and cerebellar areas but is comprised of distinct subdivisions of noradrenergic neurons.

A behaviorally validated self-report inventory to assess four types of lateral preference

Abstract: A self-report battery for the assessment of hand, eye, foot and ear preference, which has been validated against behavioral tasks designed to measure the same four types of laterality, is presented. Data showing the concordance between the inventory and the behavioral tests for a sample of 171 individuals is given. The mean degree of concordance between the behavioral and the questionnaire items was 90%. Additional analyses revealed that both forms of measurement provide similar descriptions of both individual and population lateral preference patterns. This report offers the questionnaire battery as a convenient and useful tool for the measurement of the four most common indices of laterality.

Arms Races and Escalation Some New Evidence

Abstract: Although major power arms races have been the subject of a great amount of mathematical modelling, there has been little data-based research concerning their impact on international war. This study attempts to determine whether or not these arms races affect the probability that a serious dispute between major powers will escalate to all-out war. To do this, an arms race index is constructed in the following manner: a curve-fitting technique is employed to calculate changes in arms expenditures for each major power as a function of time. The smoothed rates of increase for each of the parties to a dispute are multiplied together, yielding an index whose values will be high only if the two powers have engaged in rapid and simultaneous military expansion prior to the dispute. It was found that disputes preceded by such an arms race escalated to war 23 out of 28 times, while disputes not preceded by an arms race resulted in war only 3 out of 71 times. It was concluded that at the very least, arms races are an...

Spatial patterning of the spruce budworm

Abstract: The spatial and temporal distribution of the spruce budworm is modelled by a nonlinear diffusion equation. Two questions are considered: 1. What is the critical size of a patch of forest which can support an outbreak? 2. What is the width of an effective barrier to spread of an outbreak?

Nonspecific bronchial reactivity in occupational asthma

Abstract: The provocative concentration (PC 20 mg/ml) of methacholine required to produce a fall in the baseline FEV 1 by 20% was determined in 86 patients with occupational asthma due to exposure to western red cedar, California redwood, grain dust, or isocyanates. Fifty-seven patients were assessed at the time of diagnosis when they were symptomatic. Twenty-nine patients were studied after they had been removed from exposure for a period from 2 mo to 4 yr and were asymptomatic. Nine of the 57 patients with symptomatic asthma had repeat methacholine inhalation tests after removal from exposure. The results were compared with 33 normal healthy subjects, 30 patients with nonoccupational asthma, and 17 patients with nonindustrial chronic bronchitis. Patients with symptomatic occupational asthma had marked increase in bronchial reactivity similar to those with nonoccupational asthma. The degree of hyperreactivity decreased after removal from exposure and increased following re-exposure to the offending agents. There was little overlap in the range of PC 20 in the asthmatic compared with the nonasthmatic groups. These findings suggest nonspecific bronchial hyperreactivity is likely to be the consequence rather than the predisposing factor in occupational asthma. Methacholine inhalation test is a simple, safe, and useful procedure in the initial assessment of patients suspected to have occupational asthma before institution of time-consuming specific bronchial provocation test.

Stimulant effects of enkephalin microinjection into the dopaminergic A10 area.

Abstract: THE overt behaviour of various species is affected in different ways by opiate drugs. Mice and cats show behavioural stimulation following a systemic morphine injection whereas rats and dogs generally exhibit decreased behavioural activity1–4, although in certain conditions, stimulant effects can also be seen in the latter species4,5. Tatum et al. suggested that there are several distinct sites of action of opiate drugs in brain and that the relative dominance of one system over another determines whether the stimulant or depressant effects predominate4. Indeed, direct microinjections of morphine into the ventral tegmental area (VTA) have been shown to result in facilitation of self-stimulation behaviour whereas similar injections into the periaqueductal gray matter cause only an attenuation of this behaviour6. The discovery of endogenous ligands for opiate receptors in the brain7 has focused attention on the role of these peptides in various aspects of behaviour. Their analgesic properties following intr a ventricular and intracerebral injection are well documented8. Recently, it has been reported that infusion of α-endorphin into the substantia nigra induced stereotyped behaviour9, whereas local injections into the nucleus accumbens of the long-acting synthetic enkephalin analogue, [D-Ala2]-Met5-enkephalinamide (AME), produced an increase in locomotor activity10. We now report that infusion of AME (0.03–2.0 µg) bilaterally into the dopaminergic (DA) A10 area of the VTA induces a short-latency behavioural stimulant effect reminiscent of effects produced by stimulation of the mesolimbic DA pathway11. This effect is antagonised by pretreatment with the opiate receptor blocker naloxone.

Fine particle deposition in smooth parallel-plate channels

Abstract: The effect of electrical double-layer interactions on the rate of deposition of uniform spherical particles from an aqueous suspension in laminar flow through a smooth parallel-plate channel was measured experimentally using a radioactive tracer technique. The results obtained under initial conditions (negligible surface coverages) were compared to those predicted using a previously published theoretical model. It was found that for the deposition of negatively charged silica particles onto a positively charged plastic substrate, especially at intermediate counterion concentrations, good quantitative agreement between theory and experiment was obtained by assuming that the process was mass-transfer controlled. However, for negative particles and negative channel walls, although the theory provided an accurate qualitative description of the experimental results, the measured deposition rates were always much greater than those predicted theoretically. The evidence suggests that the primary cause of this discrepancy is the failure of the model to account for surface heterogeneity, which could result in preferential deposition onto areas of locally favorable potential or geometry. It was also found that, under the conditions of the present experiments, the release of deposited particles from the channel surface was negligible. Thus, the declining rate of accumulation with time observed in most runs could only be attributed to a diminishing rate of particle deposition.