Showing papers by "Williams College published in 1991"

Grade Inflation and Course Choice

Abstract: A conflict exists between the incentives offered to students and the institutional goal of increased science and math education. Students make their course choices in response to a powerful set of incentives: grades. These incentives have been systematically distorted by the grade inflation of the past 25 years. As a consequence of inflation, many universities have split into high- and low-grading departments. Economics, along with Chemistry and Math, tends to be low-grading. Art, English, Philosophy, Psychology, and Political Science tend to be high-grading. This paper presents evidence from nine colleges and universities that grade inflation has led to a divergence among departments in grading policies. We then discuss the results of an econometric study we conducted at Williams College of the influence of grading policies on course choice. The impact that differences in grading policies across departments have on the distribution of enrollments was also estimated, and policy implications of the findings are discussed.

Police interrogations and confessions: Communicating promises and threats by pragmatic implication.

Abstract: The present research examined the possible effects of two methods of police interrogation:maximization, a technique in which the interrogator exaggerates the strength of the evidence and the magnitude of the charges, andminimization, a technique in which the interrogator mitigates the crime and plays down the seriousness of the offense In Experiments 1 and 2, subjects read interrogation transcripts in which an interrogator used one of five methods to try to elicit a confession: a promise of leniency, threat of punishment, minimization, maximization, or none of the above As indicated on a subsequent questionnaire, maximization communicated high sentencing expectations as in an explicit threat of punishment, while minimization implied low sentencing expectations as did an explicit offer of leniency Experiment 3 demonstrated that although mock jurors discounted a confession elicited by a threat of punishment, their conviction rate was significantly increased by confessions that followed from promises or minimization Taken as a whole, these studies raise serious questions concerning the use of minimization and maximization as methods of interrogation and the confessions they produce as evidence in court

Hippocampus, context, and conditioning.

Abstract: Rabbits (Oryctolagus cuniculus) with lesions to either the hippocampus or overlying neocortex and unoperated controls underwent acquisition of the classically conditioned nictitating membrane response to a tone conditioned stimulus and an air puff unconditioned stimulus until they reached a criterion of 8 conditioned responses in any block of 10 trials. They were then returned to their cages. On the next day, they were either placed in the same context in which they underwent initial conditioning or switched to a new context that distinctly differed along olfactory, visual, and tactile dimensions. In relation to unswitched controls, rabbits with lesions to the neocortex and unoperated controls showed a disruption of conditioning when contexts were switched. In contrast, rabbits with lesions to the hippocampus performed at the same levels as unswitched controls. The results are discussed in terms of the possible role of hippocampus in coding context in classical conditioning.

Another Look at the Evidence on Money-Income Causality

Abstract: Stock and Watson's widely noted finding that money has statistically significant marginal predictive power with respect to real output (as measured by industrial production), even in a sample extending through 1985 and even in the presence of a short-term interest rate, is not robust to two plausible changes. First, extending the sample through 1990 renders money insignificant within Stock and Watson's chosen specification. Second, using the commercial paper rate in place of the Treasury bill rate renders money insignificant even in the sample ending in 1985. A positive finding is that the difference between the commercial paper rate and the Treasury bill rate does have highly significant predictive value for real output, even in the presence of money, regardless of sample. Alternative results based on forecast error variance decomposition in a vector autoregression setting confirm these findings by indicating a small and generally insignificant effect of money, and a large, highly significant effect of the paper-bill spread, on real output.

Analysis of Glucocerebrosides of Rye (Secale cereale L. cv Puma) Leaf and Plasma Membrane.

Abstract: Glucocerebrosides of whole rye (Secale cerale L. cv Puma) leaf and plasma membrane were analyzed using gas chromatography-mass spectrometry and gas chromatography following hydrolysis or as intact molecules purified by reverse-phase high performance liquid chromatography. Fatty acids of acid-hydrolyzed leaf and plasma membrane glucocerebrosides consisted of >98 weight percent saturated and monounsaturated 2-hydroxy fatty acids which contained 16 to 26 carbon atoms. The major fatty acids detected were 2-hydroxynervonic acid (24:1h), 2-hydroxylignoceric acid (24:0h), 2-hydroxyerucic acid (22:1h), and 2-hydroxybehenic acid (22:0h). Long-chain bases of alkaline-hydrolyzed glucocerebrosides consisted primarily of cis-trans isomers of the trihydroxy base 4-hydroxysphingenine (t18:1) and the dihydroxy base sphingadienine (d18:2) with lesser amounts of 4-hydroxysphinganine (t18:0) and isomers of sphingenine (d18:1). Intact, underivatized glucocerebroside molecular species of rye leaf and plasma membrane were separated into more than 30 molecular species using reverse-phase HPLC. The molecular species composition of leaf and plasma membrane were quantitatively and qualitatively similar. The major molecular species was 24:1h-t18:1 which constituted nearly 40 weight percent of leaf and plasma membrane extracts. Several other species including 22:1h-t18:1, 24:1h-t18:1 (isomer), 22:0h-t18:1, 24:1h-d18:2, and 24:0h-t18:1 each comprised 4 to 8% of the total. It is anticipated that the high performance liquid chromatography procedure developed in this study to separate intact, underivatized lipid molecular species will be useful in future studies of the physical properties and biosynthesis of plant glucocerebrosides.

Anger and the use of defense mechanisms in college students.

Abstract: It was hypothesized that experimentally induced anger would result in an increased use of defense mechanisms in college students. As predicted from the theory of defense mechanism development, the Thematic Apperception Test (TAT) stories of angered students showed a higher level of use of projection and identification, and the use of these defenses was significantly correlated with the presence of aggressive content in the stories. The results were consistent with previous studies in showing that the predominant defenses of late adolescents are projection and identification, and that men use more projection than women.

Blood and Guts: General and Trial-Specific Effects of Videotaped Crime Scenes on Mock Jurors

Abstract: A mock jury study was conducted to evaluate the effects of videotaped crime scenes on juries. Forty-eight subjects took the Juror Bias Scale and read a murder trial transcript. In addition, subjects viewed a videotape of an actual murder victim presented as the victim described in the transcript (trial-relevant video) or as one taken from another case (trial-nonrelevant video), or viewed no tape at all. Subjects filled out a questionnaire, then returned two days later to act as mock jurors in an assault case. Results indicated that exposure to the trial-relevant crime scene led subjects to set lower standards of proof and brought out individual juror biases for the prosecution. On a more general level, the crime scene tape led subjects to make lower estimates of the homicide rate, to believe the rate was increasing, and to view other crimes more seriously. Overall, the findings suggest that crime scene videos can prejudice the outcome of a criminal trial.

Recognition memory and source monitoring

Abstract: This study demonstrates a manipulation that has opposite effects on old/new recognition and source monitoring. Deep processing of target items improved performance on an old/new recognition test in which subjects were to discriminate between targets and new distractors, but it impaired performance on a source monitoring test in which subjects were to discriminate between targets and distractors that had also been deeply processed during the experimental session. We argue that the relationship between old/new recognition and source monitoring varies with the specifics of the situation. The aspects of memories that support recognition judgments are not necessarily the same as those that support source monitoring judgments, and memory performance is the joint product of what is stored in memory and how memory is tested.

Electron-microscopic cytochemical localization of diamine and polyamine oxidases in pea and maize tissues

Abstract: An electron-microscopic cytochemical method was used to localize diamine oxidase (DAO) in pea and polyamine oxidase (PAO) in maize (Zea mays L.). The method, based on the precipitation of amine-oxidase-generated H2O2 by CeCl3, was shown to be specific for DAO and PAO and permitted their localization in plant tissues with a high degree of resolution. Both enzymes are localized exclusively in the cell wall. Both DAO- and PAO-activity staining is most intense in the middle lamellar region of the wall and in cells exhibiting highly lignified walls. The oxidases could provide H2O2 for peroxidase-mediated cross-linking reactions in the cell wall and may, in this capacity, play a role in the regulation of plant growth.

The accuracy-confidence correlation in eyewitness testimony: limits and extensions of the retrospective self-awareness effect.

Abstract: This research extended Kassin's (1985) finding that retrospective self-awareness (RSA) increases the correlation between eyewitness accuracy and confidence. In Experiment 1, 91 mock witnesses saw a crime, answered questions, made an identification decision, and rated their confidence. RSA increased the accuracy-confidence correlation for witnesses who made an identification and for those who were high but not low in public self-consciousness. A 2nd experiment varied accountability and revealed that high accountability increased the accuracy-confidence correlation but that the RSA effect occurred even under low-accountability conditions. In both studies, observers could not distinguish between accurate and inaccurate witnesses. Together, these findings define the limits of the RSA effect and provide mixed support for a self-perception account of this effect.

Eustatic sea-level patterns from the Lower Silurian (Llandovery Series) of southern Norway and Estonia

Abstract: This study demonstrates the utility of checking for eustatic sea-level events correlated between passive epicontinental seas and those on the margin of orogenic activity. Bathymetric profiles interpreted on the basis of stratigraphic data from the Lower Silurian (Llandovery Series) in five districts of the Oslo region of southern Norway are compared with similar data derived from five bore-hole sites in the Baltic region of Estonia. These regions preserve extensive marine strata deposited on the Silurian continent Baltica. The data are tested for intra-regional and inter-regional conformity. Despite the fact that the Oslo region was affected by the Caledonide Orogeny, the same four highstands in sea level were recorded there as on Estonia9s comparatively stable platform. Expressed in terms of the established geochronologic standard and its faunal zones, coeval highstands in sea level occurred across Baltica during latest Rhuddanian time, in mid-Aeronian time (as marked by the basal Monograptus sedgwickii or Stricklandia lens progressa zones), in early Telychian time ( M. turriculatus or S. laevis zones), and in late Telychian time near the Llandovery-Wenlock boundary. This timing corresponds to four highstands in sea level previously documented in North America and to at least three high-stands found in South China. Claims for Early Silurian eustasy now rest on data collected from three independent paleocontinents. If the Llandovery Epoch lasted 10 m.y., then sea-level cyclicity was on the order of 2.5 m.y. A combination of tectono-eustastic and glacioeustatic causes probably was responsible for these cycles.

Epidemics and agendas: the politics of nightly news coverage of AIDS.

Abstract: We examine why the exponential growth of AIDS cases or the wide-spread professional perception of a health crisis did not move the epidemic more quickly onto the agenda of public problems One possible explanation focuses on how the national news media's construction of AIDS shaped the meaning of the epidemic for mass and elite audiences An examination of nightly news coverage by the three major networks from 1982 to 1989 reveals considerable variability and volatility in their coverage Topic-driven saturation coverage occurred only during three short periods in 1983, 1985, and 1987, when the epidemic seemed likely to affect the "general population" Only at such moments did public opinion shift and discussion and debate in government begin Otherwise, the typical AIDS story tended less to sensationalize than to reassure, largely because journalists depended upon government officials and high-ranking doctors to present them with evidence of news Such sources had interests either in avoiding coverage or in pointing toward breakthroughs; more critical sources, especially within the gay movement, had far less access to the news In concluding, we considered the prospects and pitfalls of the news media's power to shape the public agenda

Savings, Investment, and Growth in Eastern Europe

Abstract: Even modest investment rates may achieve satisfactory rates of growth in the reforming economies of Eastern Europe because their relative capital scarcity implies high rates of productivity for capital. The most serious obstacle to private investment is uncertainty about the reform process, which can potentially rule out all but the most profitable projects. This problem sharply increases the payoff from accelerating the structural reform process. Regarding savings, critical aspects are the changes in methods of financing resulting from economic reform, and the availability of foreign savings, both in the form of loans and foreign direct investment.

The multiple-shell structure of the planetary nebula NGC 6751

Abstract: An intriguing bipolar mass outflow and a faint envelope were detected spectroscopically in the planetary nebula NGC 6751 by Gieseking and Solf (1986). To study the physical structure, deep CCD images of this nebula have been obtained which detect not only the morphological counterparts of the aforementioned features but also additional faint halos extending out to a much larger radius. Long-slit echelle spectra are obtained to determine the internal motion and radial velocity, as well as low-dispersion spectra to determine the physical condition and abundances of each feature in the whole nebula. NGC 6751 is apparently a multiple-shell nebula moving through a gas-rich environment. An He abundance difference between the planetary nebula and the ambient medium and an N/O abundance ratio enhancement in the forbidden N II-bright knots in the main nebula are found. From the physical structure of the shells in NGC 6751, information is derived about the average mass-loss rates at various stages. 32 refs.

Dynamics of Late Cretaceous rocky shores (Rosario Formation) from Baja California, Mexico

Abstract: Two rocky-shore deposits are described at localities of Late Cretaceous age in Baja California, Mexico. The main locality, at Las Minas, is characterized by a carbonate matrix containing clasts derived from an underlying andesite flow. Basal boulders give way up section to smaller cobbles and silt, indicating a transgression. The biotas from the sites include encrusting forms (coralline algae, bryozoans, serpulids, ostreids, spondylids), pholadid bivalve borings, and several nestling and mobile taxa. The well exposed boulder zone contains clusters of nestling pectinids preserved in growth position. This is the first such observation from an ancient rocky shore. Echinoids also lived within the relatively stable boulder interstices. Rocky-shore biotas of Late Cretaceous age from around the world contain many elements in common, including large encrusting oysters, spondylids, serpulids, rhynconellid brachiopods, and echinoids. Other groups common to rocky shores today are found at only some Cretaceous localities (e.g., barnacles, trochid and cerithiid gastropods, limpets, chitons). More archaic taxa, such as crinoids and large inarticulate brachiopods, are rarely represented at the known Cretaceous localities. Reconstructions of the biotas of ancient rocky shores offer a new avenue for the study of evolution on hard substrates. As the number and quality of described rocky-shore localitiesmore » increases, it will be possible to put into a broader context evolutionary trends derived strictly from hard-grounds or other hard-substrate types.« less

A particle-based computational model of cloth draping behavior

Abstract: We report on a particle-based model that we have used to reproduce the draping behavior of cloth. The model utilizes a microscopic representation that directly models the interactions between the yarns in the weave of the material, rather than using a macroscopic continuum approximation to the material. Because the model incorporates the micro-structure of the material, it can be easily extended to incorporate important material nonlinearities such as the frictionally-based mechanical interactions between fibers that give cloth its ability to be shaped, pressed, and formed.

The effects of postnatal caffeine exposure on growth, activity and learning in rats.

Abstract: Caffeine is both ingested by pregnant women in their third trimesters and administered therapeutically to premature infants to stimulate respiration. This experiment attempted to delineate any persistent effects of low dose caffeine exposure during the first week of life in rats, since this time period provides an animal model equivalent to the human third trimester or premature infant exposure. Rat pups who had received either 1 or 9 mg/kg of caffeine during the first week of life grew more slowly, were hypoactive at two weeks of age, and were impaired on an operant spatial learning task as adults. Adding visual cues to the operant task did not improve their performance. The timing of the appearance of developmental landmarks, adult body weight and adult brain weight, however, were not affected by postnatal caffeine exposure. The persistent behavioral deficits noted after postnatal caffeine exposure were all opposite in direction to the acute effects of caffeine, and similar to the effects of adenosine. Thus the behavioral deficits reported here may reflect an upregulation of developing adenosine receptors that persists into adulthood subsequent to early chronic postnatal caffeine exposure.

Why Does the Paper-Bill Spread Predict Real Economic Activity?

Abstract: Evidence based on the past three decades of U.S. experience shows that the difference between the interest rates on commercial paper and Treasury bills has consistently borne a systematic relationship to subsequent fluctuations of nonfinancial economic activity. This interest rate spread typically widens in advance of recessions, and narrows again before recoveries. The relationship remains valid even after allowance for other financial variables that previous researchers have often advanced as potential business cycle predictors. This paper provides support for each of three different explanations for this predictive power of the paper?bill spread. First, changing perceptions of default risk exert a clearly recognizable influence on the spread. This influence is all the more discernable after allowance for effects associated with the changing volume of paper issuance when investors view commercial paper and Treasury bills as imperfect portfolio substitutes -- a key assumption for which the evidence introduced here provides support. Second, again under conditions of imperfect substitutability, a widening paper-bill spread is also a symptom of the contraction in bank lending due to tighter monetary policy. Third, there is also evidence of a further role for independent changes in the behavior of borrowers in the commercial paper market due to their changing cash requirements over the course of the business cycle.

The Equivalence of Two Semantic Definitions for Inheritance in Object-Oriented Languages

Abstract: A simple language is presented which supports inheritance in object-oriented languages. Using this language, the definitions for the semantics of inheritance given in [CHC90] and [Mit90] are compared and shown to be equivalent. The equivalence is shown by presenting and comparing two denotational semantics of the simple language which capture the essence of each of the earlier semantics.

Attenuation of age-related conditioning deficits in humans by extension of the interstimulus interval.

Abstract: Young (17-22 years) and older (61-86 years) persons underwent classical conditioning of the eye-blink response to a tone conditioned stimulus (CS) and an airpuff unconditioned stimulus (UCS) at 1 of 3 interstimulus intervals (ISIs; 400, 650, and 900 ms). As in a previous study, older subjects conditioned more slowly and emitted fewer conditioned responses at the optimal 400-ms ISI. At longer ISIs, however, this age-related disruption of classical conditioning was attenuated. These differences in conditioning were not due to nonassociative factors, such as sensitivity to the tone CS or airpuff UCS or to differences in spontaneous blink rate, nor were they due to differences in general cognitive abilities. The results are discussed in terms of the role of temporal relationships between stimuli in conditioning across the life span.

CHARMed, but not convinced: Comment on Metcalfe (1990).

Abstract: Metcalfe (1990) proposed her Composite Holographic Associative Recall Model (CHARM) as a model of eyewitness suggestibility. CHARM has many appealing properties and performed well in simulations of suggestibility. Most important, CHARM provides a formal mechanism by which suggestions impair memory without affecting performance on McCloskey and Zaragoza's (1985a) Modified Tests. Nonetheless, a number of shortcomings limit CHARM's usefulness as a model of suggestibility: (a) in the simulations, control terms differ from those in human studies; (b) the model makes a counterintuitive prediction about performance on a recognition pair composed of an event detail and its control term; (c) CHARM models association, not remembering; and (d) most of the intelligence in the simulations lies in the programmer rather than in CHARM itself, which limits the model's constraint on memory blending