Showing papers by "Williams College published in 1995"

Preference Reversals Due to Myopic Discounting of Delayed Reward

Abstract: A basic stationarity axiom of economic theory assumes stable preference between two deferred goods separated by a fixed time To test this assumption, we offered subjects choices between delayed rewards, while manipulating the delays to those rewards Preferences typically reversed with changes in delay, as predicted by hyperbolic discounting models of impulsiveness Of 36 subjects, 34 reversed preference from a larger, later reward to a smaller, earlier reward as the delays to both rewards decreased We conclude that the stationarity axiom is not appropriate in models of human choice

Introduction, dispersal and potential impacts of the green crab Carcinus maenas in San Francisco Bay, California

Abstract: The North Atlantic portunid crab Carcinus maenas (Linnaeus, 1758) has invaded the North Pacific Ocean following more than two centuries of global dispersal due to human activities. C. maenas was first collected in San Francisco Bay, California, in 1989–1990, where its distribution and prey selectivity were investigated in 1992–1994. It has become abundant in shallow, warm lagoons (which as favorable and retentive microhabitats may have served as invasion incubators) and spread throughout the north, central and south bays. It may have arrived in ballast water, on fouled ships, amongst algae with imported live bait or lobsters, or by intentional release; genetic comparisons of the Bay population with possible source populations may aid in defining the transport mechanism. C. maenas' eurytopic nature, its high breeding potential, and its diet and feeding behavior suggest the potential for extensive ecosystem alterations through predator-prey interactions, competition, disturbance, and indirect effects. Although both negative economic impacts through reduction or disruption of fisheries and positive impacts of providing bait and human-food fisheries have been documented in a few regions, the potential economic impacts in San Francisco Bay remain largely unknown.

With Malice toward Some: How People Make Civil Liberties Judgments

Abstract: Preface: Political tolerance and democratic life Part I. Theoretical Background and Overview: 1. Political tolerance and democratic practice 2. Antecedent considerations and contemporary information 3. Thinking and mood Part II. Contemporary Information and Political Tolerance Judgments: 4. Tolerance judgments and contemporary information - the basic studies Appendix 4A. The basic experiments - manipulation checks Part III. Refining the Model - The Role of Antecedent Conserations as Individual Differences: 5. Threat and political tolerance 6. Democratic values as standing decisions and contemporary information 7. Source credibility, political knowledge and animus in making tolerance judgments - the Texas experiment 8. Individual differences: The influence of personality Part IV. Implications and Conclusions: 9. Intensity, motivations, and behavioral intentions 10. Human nature and political tolerance Appendices Bibliography.

Racial identity, academic achievement, and the psychological well-being of economically disadvantaged adolescents.

Abstract: The relation between racial identity and personal psychological functioning was examined within the framework of the "racelessness" construct proposed by Fordham and Ogbu (S. Fordham, 1988; S. Fordham & J. U. Ogbu, 1986). These researchers have proposed that academically successful African American students achieve their success by adopting behaviors and attitudes that distance them from their culture of origin, resulting in increased feelings of depression, anxiety, and identity confusion. Studies 1 and 2 describe the development of the Racelessness Scale (RS) designed to test these assumptions. Study 2 also investigated Race X Achievement level differences in students' responses to the RS. In Study 3, correlations between the RS and measures of depression, self-efficacy, anxiety, alienation, and collective self-esteem were assessed. The pattern of results in Study 2 suggest that the behaviors and attitudes described by Fordham and Ogbu are common to high-achieving adolescents and not specific to African Americans. However, racial differences in the pattern of associations between the RS and measures of depression suggest that racelessness may have important psychological consequences for African American adolescents.

The Stories Children Tell: Making Sense of the Narratives of Childhood

Abstract: The world of children's stories why children tell stories perspectives on narratives the kinds of stories children tell the origins of story-telling developing a narrative voice we are the stories we tell fostering narrative development.

Biogeography and dispersal of coastal marine organisms: experimental studies on a replica of a 16th-century sailing vessel

Abstract: Observational and experimental studies were conducted on the dispersal of fouling organisms on a replica of a 16th-century sailing vessel along an 800 km transect from Yaquina Bay, Oregon to San Francisco Bay, California. The vessel sailed between four bays at slow speeds (3.5 to 4 knots), resided in each bay for approximately 30 d, and spent 1 to 3 d in the open ocean travelling between ports. Natural hull fouling and experimental fouling panels placed on the vessel were sampled upon departure and arrival at each port. All common fouling species survived the open sea voyages between the harbors, with largely no ecologically significant changes in abundance nor significant losses in overall diversity detected. In one port the vessel settled upon the harbor floor periodically; several entrained benthic organisms were then transported 390 km to the next port. Slow-moving, fouled sailing vessels of relatively long port residencies may have significantly altered the distributions of marine and estuarine organisms not only globally (leading to the invasions of non-native species) but also along continental margins (leading to the alteration of aboriginal patterns of distribution). Shipping traffic may further play an important role in gene flow between isolated populations of obligate estuarine organisms, particularly those with non-planktonic larvae.

An Empirical Analysis of the Welfare Magnet Debate Using the Nlsy

Abstract: This paper examines the extent to which differences in welfare generosity across states leads to interstate migration. Using microdata from the National Longitudinal Survey of Youth (NLSY) between 1979 and 1992, we employ a quasi-experimental design that utilizes the categorical eligibility of the welfare system. The pattern of cross-state moves among poor single women with children who are likely to be eligible for benefits is compared to the pattern among other poor households. We find little evidence indicating that welfare-induced migration is a widespread phenomenon.

Phenotypic design, plasticity, and ecological performance in two tadpole species

Abstract: This study relates community ecology to phenotypic design in two species of hylid tadpole that share larval habitat on the rocky shoreline of Isle Royale, Michigan. The ecological results indicate that the two species partition a competition-predation gradient on the shore. Pseudacris crucifer is mostly high on the shore at low density in persistent pools with predators (dragonfly larvae, Aeshnajuncea); tadpoles have low individual growth rates and metamorphose late at large body size. Pseudacris triseriata is more variable in growth and development but typically grows more rapidly and metamorphoses earlier. All P. crucifer that attain metamorpho- sis emerge from pools with Aeshna, whereas P. triseriata metamorphose from a mixture of pools with and without predators. A reciprocal transplant experiment showed that both species survived poorly in the upper level pools with predators, which indicates that predation is more important there. The experiment did not show strong competition between the two species in either kind of pool. The phenotypes, including plasticity, of the two species are consistent with their ecological differences. Pseudacris triseriata has traits that functional arguments suggest should assist in processing food: in natural populations it hatches at large size, feeds actively and conspicuously, and has a relatively round body and small tail muscle and tail fin. Pseudacris crucifer has the opposite suite of characters, which functional arguments suggest favor predator avoidance. The variation in larval habitat correlated with differences in plasticity. In the trans- plant experiment, P. crucifer showed little change in phenotype, whereas P. triseriata reduced activity and increased tail fin and tail muscle size in the presence of Aeshna. This study illustrates that ecological differences in tadpoles correlate with behavioral and morphological phenotypes and that phenotypic traits can be used to predict ecological performance in manipulative experi- ments in natural settings. One of the underlying theses of ecology asserts that we can understand the control of communities in terms of interactions, notably competition and preda- tion, between the component populations. A rich experimental tradition has tested this proposition, focusing on interactions among populations. The impor- tance of causal factors is judged according to the impact on population dynamics, judged by experimentally excluding or adding member species in the community (Gause 1934; Connell 1961; Wilbur 1972). This experimental approach, termed phenomenological, has established the causal bases for an increasing number of natural patterns in communities, including the differences in habitat among closely related species.

PolyTOIL: A Type-Safe Polymorphic Object-Oriented Language

Abstract: PolyTOIL is a new statically-typed polymorphic object-oriented programming language which is provably type-safe. By separating the definitions of subtyping and inheritance, providing a name for the type of self, and carefully defining the type-checking rules, we have obtained a language which is very expressive while supporting modular type-checking of classes. The matching relation on types, which is related to F-bounded quantification, is used both in stating type-checking rules and expressing the bounds on type parameters for polymorphism. The design of PolyTOIL is based on a careful formal definition of type-checking rules and semantics. A proof of type safety is obtained with the aid of a subject reduction theorem.

Unrealistic Optimism: Self-Enhancement or Person Positivity?

Abstract: Researchers interested in unrealistic optimism disagree on whether the phenomenon reflects self-enhancement or person positivity. Past research in this area has used a paradigm that confounds the self/other dimension with the individual aggregate dimension, making it difficult to determine which alternative is correct. Two studies examined whether people are unrealistically optimistic only for their own futures or whether they are unrealistically optimistic for the future of any individual. Study 1 revealed that, in comparison with an aggregate of same-sex peers, participants were unrealistically optimistic for their own and a close friend's futures but not for the future of a non-self-relevant other Study 2 employed unconfounded measures and demonstrated that, in comparison with other individual social objects, participants continued to be unrealistically optimistic for their own futures. These results suggest that unrealistic optimism is a form of self-enhancement rather than person positivity bias.

Enhanced early detection and enumeration of zebra mussel (Dreissena spp.) veligers using cross-polarized light microscopy

Abstract: Zooplankton with calcareous skeletons are birefringent under cross-polarized light, and thus this technique can be quite useful, indeed sometimes almost essential, for the detection and enumemeration of these types of organisms in plankton samples. A simple and inexpensive application of this technique is described and illustrated with quantitative examples from research on the veligers of the zebra mussel Dreissena polymorpha (Pallas). The time required to detect veligers in plankton samples was decreased by an order of magnitude; the accuracy of counts was substantially improved (15% more than controls), and the time required for counts was greatly reduced (41% of control times). This technique is especially useful in situations in which veligers are difficult to find or see (e.g., at low densities, in samples ‘cluttered’ with extraneous organisms or material) or when the investigator is inexperienced with plankton sampling and planktonic organisms. The major limitations are its inability to discriminate among various bivalve species that have planktonic larvae and the similar appearance of ostracods which also have calcareous shells. Expanded use of this technique should (1) increase our ability to use plankton sampling for the early detection of veligers during range expansion and reproductive cycles and (2) permit more accurate estimates of veliger abundance.

Planar Hybrid Systems

Abstract: The design of nonlinear dynamical systems to realize the desired behavior of devices and processes is a fundamental problem that is often approached from the perspective of control theory. Control provides a large set of tools for tackling these design problems, but some classes of problems have remained resistant to these methods. This paper discusses a theory of hyb r id sys t ems that extends the concept of a smooth dynamical system to a context in which there is a mixture of continuous time and discrete time elements. This is particularly appropriate for the description of "switching systems" in which digital control is applied to change continuous control laws on a time scale much faster than the dynamical evolution of the device being controlled. Digital control makes it (relatively) easy to build devices in which the applied control is any computable function of system measurements. This enormously widens the scope for the system designs that can be implemented, but the additional design freedom brings with it many more design parameters. Consequently, we seek better theory to provide guiding principles that can help us cope with this new found freedom. This paper is a step in this direction. We consider hybrid systems with two dimensional phase spaces subject only to mild genericity requirements, and describe the types of long term dynamical phenomena displayed by these systems.

Effects of a hurricane on survival and orientation of large erect coral reef sponges

Abstract: In October 1988, Hurricane Joan struck reefs in the San Blas Island, Panama, where hurricanes had never been recorded. Effects on large erect sponges were dramatic. For several years before the hurricane, the three most common sponges had been studied, providing pre-storm data on population structure and dynamics. Nearly half the individuals and biomass of three species were lost in the storm. The species were not affected in the same way, even though they are all of erect branching growth forms. Iotrochota birotulata lost significantly more individuals chan Amphimedon rubens (57.6% vs 42.9%), which lost significantly more individuals than Aplysina fulva (31.6%). Patterns of biomass loss were very different, with both Iotrochota and Aplysina suffering losses of about 50%, but Amphimedon losing only 4.9%. Patterns of loss appear to be related to differences between species in the relative proportions of spicules (siliceous) and spongin (protein) in skeletal fibers and by differences in the speed and success rate of fragment reattachment. The incidence of toppling due to base failure varied among the six most common large erect sponge species, with significantly less toppling of the two species with skeletons composed solely of spongin. Clones of Iotrochota birotulata characterized by harrow branches suffered disproportionately greater losses than clones with more robust branches. The abundance of very small sponges, possibly developed from sexually produced larvae, was an order of magnitude higher after the storm than before.

Echoes of the Baby Boom and Bust: Recent and Prospective Changes in Living Alone among Elderly Widows in the United States*

Abstract: Today the great majority of noninstitutionalized elderly widows live alone, a striking increase from a quarter-century ago. A noticeable difference has occurred, however, in trends by age; the proportion of the young-old widows living alone is starting to decline. while that of the old-old continues to increase. We use a model suggested by earlier studies to explain the emergence of this difference, and assess the prospects of its continuing over the next three decades. We find that the recent differential change in the proportions of younger and older widows living alone is due primarily to a differential change in kin availability that has emerged as the baby boomers’ parents have begun to reach retirement age. Over the next decade, the same type of differential change by age in kin availability will continue; living alone is likely to become less common among young-old than among old-old widows, in a reversal of the pattern of the last quarter-century. In the first two decades of the next century, as the baby boom affects kin availability among the old-old, and as the subsequent baby bust affects that among the young-old, the age pattern of living arrangements among elderly widows will reverse once again.

Reconfiguring closed polygonal chains in Euclideand-space

Abstract: Consider the problem of moving a closed chain ofn links in two or more dimensions from one given configuration to another. The links have fixed lengths and may rotate about their endpoints, possibly passing through one another. The notion of a "line-tracking motion" is defined, and it is shown that when reconfiguration is possible by any means, it can be achieved byO(n) line-tracking motions. These motions can be computed inO(n) time on real RAM. It is shown that in three or more dimensions, reconfiguration is always possible, but that in dimension two this is not the case. Reconfiguration is shown to be always possible in two dimensions if and only if the sum of the lengths of the second and third longest links add to at most the sum of the lengths of the remaining links. AnO(n) algorithm is given for determining whether it is possible to move between two given configurations of a closed chain in the plane and, if it is possible, for computing a sequence of line-tracking motions to carry out the reconfiguration.

Chinatown: Conflicting Images, Contested Terrain

Abstract: Ever since Chinese immigrants in America began forming communities in the mid- to late-nineteenth century, their residential, business, and cultural space, generally referred to as "Chinatown," has been layered with imagery. These images, largely negative and demeaning, have usually been flamed by observers who did not live in Chinatown, and who had little connection to or stake in the community. Conversely, they had reason to want the elimination of the Chinese-American community in the United States, or at least its complete segregation. This, along with the passing of restrictive immigration bills, was a primary tactic of the exclusionist movement's drive to keep Chinese immigrants from entering American society. Unfortunately, it has been these representations that have dictated the terms of the discourse concerning American Chinatowns and that have mediated the perceptions of Chinatown held by many Chinese, Chinese-Americans, and Euro-Americans. Portrayals of Chinatown constructed by observers and writers who focused on what they found repugnant about Chinese life in America actually reveal more about the observers than the observed and disclose broader racial and class biases. Analysis of such representations of Chinese communities in the United States readily indicate that conflicting "Chinatown images" are part of much larger sociopolitical agendas, which make of Chinatown a "contested terrain" in the attempt to define and reinforce notions of American and Chinese culture. Similarly, when Chinese writers sought to refute the charges leveled against the Chinese immigrant community, they were put in the position of having to define what Chinatown was not, rather than developing a language in the popular discourse that could establish what Chinatown was. This essay presents a selection of representations of American Chinatowns found in a variety of American and Chinese sources, ranging from popular periodicals, transcripts of government hearings, labor pamphlets, travel diaries, and film. By placing these images in their historical context, it becomes clear that impressions and depictions of "Chinatown" have been used for sociopolitical purposes that have much more to do with the agendas of the framers of these representations than they do with the residents of Chinatown. The term "conflicting images" has two layers of meaning in this piece. In some cases it refers to the contrast between representations of Chinatown and Euro-American communities, and at other times it points to examples of Euro-American hostility toward the Chinese immigrant community, referring to the social conflict between the two communities. In both usages, these images served as "weapons" in the larger sociopolitical "battles" that made up the anti-Chinese movement in which difference was used for negative political purposes. Chinatown became a site of negation and definition. Conflicting images were used to portray a community that was forever foreign to American sensibilities and completely unacceptable. At the same time, these images perversely helped define what American communities "ought" to be like: clean, without odor, safe, and Christian. Viewed in this manner, portrayals of Chinatown had as much to do with Euro-American images of themselves as they did of the Chinese immigrant community, a community under siege from both sides of this cultural encounter. Some of the most virulent images of Chinatown appeared in popular periodicals, government documents, and labor union pamphlets of the late-nineteenth and early-twentieth centuries. These images tended to cluster around a number of common themes: the physical "mysteriousness" of Chinatown, unsanitary living conditions, immoral activities, and the general Otherness of the Chinese themselves, all of which contrasted with familiar idealized images of "American" communities. For example, Chinatown was described by one travel magazine writer as, "an agglomeration of Oriental paganism, [with] reeking sidewalks, foul with unknown trash, the nauseous odors vomited from black cellars; the wilderness of alleys. …

Sponge-feeding by the Caribbean starfish Oreaster reticulatus

Abstract: The common Caribbean starfish Oreaster reticulatus (Linnaeus) feeds on sponges by everting its stomach onto a sponge and digesting the tissue, leaving behind the sponge skeleton. In the San Blas Islands, Republic of Panama, 54.2% of the 1549 starfish examined from February 1987 to June 1990 at eight sites were feeding, and 61.4% of these were feeding on sponges, representing 51 species. Sponges were fed on disproportionately heavily in comparison to their abundance, which was only 9.7% of available prey. In feeding choice experiments, 736 pieces of 34 species of common sponges from a variety of shallow-water habitats, and also 9 ind of a coral, were offered to starfish in individual underwater cages. Acceptance or rejection of sponge species was unambiguous for 31 of the 34 species, and there was a clear relationship between sponge acceptability and sponge habitat. Starfish ate 16 of 20 species that normally grow only on the reefs, but only 1 of 14 species that live in the seagrass meadows and rubble flats surrounding the reefs. The starfish live in the seagrass meadows and rubble flats, and avoid the reefs, and so the acceptable reef sponges are generally inaccessible until a storm fragments and transports them into starfish habitat. After Huricane Joan washed fragments of reef sponges into a seagrass meadow in October 1988, starfish consumed the edible species. When the seagrass meadow was experimentally seeded with tagged reef sponge fragments in June 1994, O. reticulatus consumed edible species and accumulated in the area seeded. Reef sponges that were living in a seagrass meadow, from which O. reticulatus had been absent for at least 4 yr (from 1978 to 1982), were eliminated when the starfish migrated into the area, and the sponges have been unable to recolonize up to June 1994. O. reticulatus feeding and habitat preferences appear to restrict distributions of many Caribbean reef sponge species to habitats without O. reticulatus and may have exerted significant selective pressure on defences of those sponges that live in O. reticulatus habitats.

Secondary chemistry of hybrid and parental willows: Phenolic glycosides and condensed tannins in Salix sericea, S. eriocephala , and their hybrids

Abstract: Salix sericea andS. eriocephala differ markedly in secondary chemistry.S. sericea produces phenolic glycosides, salicortin and 2′-cinnamoylsalicortin, and low concentrations of condensed tannin. In contrast,S. eriocephala produces no phenolic glycosides, but high concentrations of condensed tannins. Hybrid chemistry is intermediate for both types of chemicals, suggesting predominantly additive inheritance of these two defensive chemical systems from the parental species. However, there is extensive variation among hybrids. This variation may be due to genetic variation among parental genotypes, which genes were passed on, or to subsequent back-crossing. The differences in chemistry are likely to exert a strong effect on the relative susceptibility of hybrid and parental willows to herbivores.

Superrigidity of lattices in solvable Lie groups

Abstract: Let Γ be a closed, cocompact subgroup of a simply connected, solvable Lie groupG, such that AdG Γ has the same Zariski closure as AdG. If α: Γ → GLn(ℝ) is any finite-dimensional representation of Γ, we show that α virtually extends to a representation ofG. (By combining this with work of Margulis on lattices in semisimple groups, we obtain a similar result for lattices in many groups that are neither solvable nor semisimple.) Furthermore, we show that if Γ is isomorphic to a closed, cocompact subgroup Γ′ of another simply connected, solvable Lie groupG′, then any isomorphism from Γ to Γ′ extends to a crossed isomorphism fromG toG′. In the same vein, we prove a more concrete form of Mostow's theorem that compact solvmanifolds with isomorphic fundamental groups are diffeomorphic.

Comparative studies on the Mauthner cell of teleost fish in relation to sensory input.

Abstract: Most physiological and behavioral studies of the Mauthner cells have used the goldfish and a few other fish from the superorder Ostariophysi, series Otophysi (=otophysans). We first provide some background and recent findings on the Mauthner cells of otophysan fish and then compare this information to that known about the Mauthner cells in certain non-otophysan fish. These comparisons are meant to provide the impetus for a comparative approach to understanding the role of the Mauthner cells in behavior.

Preserving leaves for tannin and phenolic glycoside analyses: A comparison of methods using three willow taxa.

Abstract: Members of the Salicaceae often produce phenolic glycosides and condensed tannins. There is much debate on the best method for the preservation of leaf material prior to chemical analysis. Published results indicate freeze-drying, a method commonly used for tannin analysis, may be inappropriate for phenolic glycosides, unless done in a manner to prevent thawing during the drying process. Another commonly employed method, air-drying, is appropriate for phenolic glycosides but inappropriate for condensed tannins. I present evidence using willow leaves that demonstrates that: (1) leaves freeze-dried in external flasks without temperature control contain lower concentrations of phenolic glycosides (salicortin and 2′-cinnamoylsalicortin), (2) air-dried leaves have reduced concentrations of condensed tannins, while (3) vacuum-dried fresh leaves have high concentrations of both phenolic glycosides and condensed tannins. Freeze-drying caused salicortin and 2′-cinnamoyl salicortin concentrations to drop by 20 mg/g and 4 mg/g, respectively. Salicin, a product of salicortin and 2′-cinnamoyl salicortin degradation, is absent in vacuum-dried leaves, present in air-dried leaves and very high in freeze-dried leaves. Thus, the presence of salicin in this system is an artifact of the preservation technique. Condensed tannin concentrations dropped nearly 20 mg/g when leaves were air-dried. Thus, vacuum-drying fresh leaves allows researchers to quantify phenolic glycosides and condensed tannins from the same leaf material.

Unknotting tunnels in hyperbolic 3-manifolds

Abstract: An unknotting tunnel in a 3-manifold with boundary is a properly embedded arc, the complement of an open neighborhood of which is a handlebody. A geodesic with endpoints on the cusp boundary of a hyperbolic 3-manifold and perpendicular to the cusp boundary is called a vertical geodesic. Given a vertical geodesic in a hyperbolic 3-manifold M, we find sufficient conditions for it to be an unknotting tunnel. In particular, if the vertical geodesic corresponds to a 4-bracelet, 5-bracelet or 6-bracelet in the universal cover and has short enough length, it must be an unknotting tunnel. Furthermore, we consider a vertical geodesic that satisfies the elder sibling property, which means that in the universal cover, every horoball except the one centered at infinity is connected to a larger horoball by a lift of the vertical geodesic. Such a vertical geodesic with length less than ln(2) is then shown to be an unknotting tunnel.

Do taxes on large firms impede growth? evidence from ghana

Abstract: Many developing countries pursue policies that treat large and small firms differently. For example, large firms may be subject to a value added tax while small firms are explicitly exempted. Moreover, governments often find it impractical to collect taxes from the smallest enterprises; this may increase the tax burden for larger firms, whose compliance can be enforced. Such policies clearly affect the size distribution of firms. But how great is the impact on macro variables? How large are the resulting inefficiencies? And what are the dynamic effects on capital accumulation and economic growth? This paper uses a dynamic general equilibrium variant of the Lucas (1978) span-of-control model to address such questions. The model is matched to data from the Ghanaian manufacturing sector. As a policy experiment, alternative tax and regulatory regimes are compared. The model shows that a policy disproportionately penalizing large firms can reduce output by nearly one-half, compared with an alternative policy regime in which all firms face the same taxes and regulatory costs.

A Skew Product Entropy for Nonsingular Transformations

Abstract: We define a skew product entropy for conservative nonsingular transformations, show that it takes values in {0, 00} and use it to distinguish two classes on nonsingular transformations. Binary and ternary type Ulx odometers have zero skew product entropy, while nonsingular K-automorphisms have infinite skew product entropy.

Privatization of natural monopoly public enterprises: The regulation issue

Abstract: The paper presents a simple model that calculates — as a percentage of industry revenues — the welfare gains or losses that might ensue when a public enterprise natural monopoly is replaced by a profit maximizing private monopoly. The model incorporates both the pre-privatization demand elasticity and production efficiency changes subsequent to privatization. The magnitude of the welfare changes suggests that allocative efficiency improvements do not provide a compelling rationale for post-privatization regulation. Greater consideration must be given to other regulatory objectives including distributional concerns and the need to create an institutional environment that encourages investment.

Differential behavioral effects of the neuroactive steroid allopregnanolone on neonatal rats prenatally exposed to alcohol.

Abstract: The effects of prenatal alcohol exposure on the behavioral response to the neuroactive steroid allopregnanolone (3 alpha-hydroxy-5 alpha-pregnan-20-one) were investigated in neonatal rats. Two behaviors were assessed: retention of an odor conditioning task and production of ultrasonic vocalizations after brief maternal separation. Subjects from one of the three prenatal conditions (lab chow, alcohol, or pair-fed) received either no injection or an ICV injection of vehicle or one of three doses (1.25-5.0 micrograms) of allopregnanolone either 20 min prior to or immediately after training in an appetitive odor association paradigm. Retention was assessed 1 h later in a two-choice odor preference chamber. Posttraining injections of allopregnanolone caused a dose-dependent impairment in retention in the odor task, but there was no differential sensitivity to allopregnanolone in the alcohol-exposed offspring. All pretraining injections, including the vehicle, resulted in impairments in retention on the task, suggesting an impairment due to stress but not due to allopregnanolone. Allopregnanolone also reduced ultrasonic vocalizations after brief maternal separation in all subjects in a second experiment, but alcohol-exposed offspring displayed a dose-dependent shift to the right in their anxiolytic response to this neurosteroid. This decreased sensitivity suggests that prenatal alcohol exposure may cause a decrease in the density or affinity of the GABA receptors involved in stress response, but not cognitive processes, at this age.

Classical conditioning in patients with Alzheimer's disease : a multiday study

Abstract: Previous studies demonstrated that patients with Alzheimer's disease (AD) do not acquire the classically conditioned eyeblink response. These studies, however, were only tested over a single conditioning session and, hence, raise the question of whether AD patients are capable of acquiring the response if sufficient training is given. This question may be of some importance whether AD patients can ultimately acquire the response has implications for the underlying neurobiological deficit in disrupted conditioning in AD. This study tested AD patients and age-matched controls over 4 days. As in previous studies, AD patients performed significantly worse than controls on Day 1, but by Day 4, they were not significantly different from controls. Subsequent testing indicated that these effects were not due to nonassociative variables such as changes in sensitivity to stimuli or disruption of the motor response. Also, it was reported that neither AD patients nor controls showed any evidence of acquisition in an explicitly unpaired paradigm, suggesting that neither pseudoconditioning nor sensitization is contributory. Data are discussed in terms of the possible role of the hippocampus in mediating conditioning deficits in AD patients.