Visual-auditory differences in duration discrimination of intervals in the subsecond and second range

A common finding in time psychophysics is that temporal acuity is much better for auditory than for visual stimuli. The present study aimed to examine modality-specific differences in duration discrimination within the conceptual framework of the Distinct Timing Hypothesis. This theoretical account proposes that durations in the lower milliseconds range are processed automatically while longer durations are processed by a cognitive mechanism. A sample of 46 participants performed two auditory and visual duration discrimination tasks with extremely brief (50-ms standard duration) and longer (1000-ms standard duration) intervals. Better discrimination performance for auditory compared to visual intervals could be established for extremely brief and longer intervals. However, when performance on duration discrimination of longer intervals in the 1-s range was controlled for modality-specific input from the sensory-automatic timing mechanism, the visual-auditory difference disappeared completely as indicated by virtually identical Weber fractions for both sensory modalities. These findings support the idea of a sensory-automatic mechanism underlying the observed visual-auditory differences in duration discrimination of extremely brief intervals in the millisecond range and longer intervals in the 1-s range. Our data are consistent with the notion of a gradual transition from a purely modality-specific, sensory-automatic to a more cognitive, amodal timing mechanism. Within this transition zone, both mechanisms appear to operate simultaneously but the influence of the sensory-automatic timing mechanism is expected to continuously decrease with increasing interval duration.

Time-order errors and standard-position effects in duration discrimination: An experimental study and an analysis by the sensation-weighting model

Studies have shown that the discriminability of successive time intervals depends on the presentation order of the standard (St) and the comparison (Co) stimuli. Also, this order affects the point of subjective equality. The first effect is here called the standard-position effect (SPE); the latter is known as the time-order error. In the present study, we investigated how these two effects vary across interval types and standard durations, using Hellström’s sensation-weighting model to describe the results and relate them to stimulus comparison mechanisms. In Experiment 1, four modes of interval presentation were used, factorially combining interval type (filled, empty) and sensory modality (auditory, visual). For each mode, two presentation orders (St–Co, Co–St) and two standard durations (100 ms, 1,000 ms) were used; half of the participants received correctness feedback, and half of them did not. The interstimulus interval was 900 ms. The SPEs were negative (i.e., a smaller difference limen for St–Co than for Co–St), except for the filled-auditory and empty-visual 100-ms standards, for which a positive effect was obtained. In Experiment 2, duration discrimination was investigated for filled auditory intervals with four standards between 100 and 1,000 ms, an interstimulus interval of 900 ms, and no feedback. Standard duration interacted with presentation order, here yielding SPEs that were negative for standards of 100 and 1,000 ms, but positive for 215 and 464 ms. Our findings indicate that the SPE can be positive as well as negative, depending on the interval type and standard duration, reflecting the relative weighting of the stimulus information, as is described by the sensation-weighting model.

Understanding Racial Segregation: What is known about the Effect of Housing Discrimination

A central purpose of this chapter is to assess whether the available empirical evidence supports the view that current levels of housing discrimination are a significant contributor to residential segregation in U.S. cities and metropolitan areas. Through the course of this chapter, the reader will find that the empirical patterns of racial segregation in the U.S. are often inconsistent the available evidence on housing discrimination. Admittedly, strong evidence exists that both housing discrimination exists today and that housing discrimination throughout much of the Twentieth Century was central to creating the high levels of segregation that we observe in U.S. metropolitan areas today, but the appropriate policy responses may differ dramatically depending upon how these two phenomena are currently interrelated.

Housing Discrimination in Metropolitan America: Findings from the Latest National Paired Testing Study

During the summer and fall of 2000, local fair housing organizations in twenty major metropolitan areas nationwide conducted a total of 4,600 paired tests, directly comparing the treatment that African Americans and Hispanics receive to the treatment that whites receive when they visit real estate or rental offices to inquire about available housing. This study, which was sponsored by the U.S. Department of Housing and Urban Development and conducted by the Urban Institute, provides the most complete and up-to-date information available about the persistence of housing market discrimination against African American and Hispanic homeseekers in large urban areas of the United States today and about the progress we have made in combating discrimination over the last decade.

An Economic Theory of Mortgage Redemption Laws

Redemption laws give mortgagors the right to redeem their property following default for a statutorily set period of time. This paper develops a theory that explains these laws as a means of protecting landowners against the loss of non-transferable values associated with their land. A longer redemption period reduces the risk that this value will be lost but also increases the likelihood of default. The optimal redemption period balances these effects. Empirical analysis of cross-state data from the early twentieth century suggests that these factors, in combination with political considerations, explain the existence and length of redemption laws.

An Economic Theory of Mortgage Redemption Laws

Redemption laws give mortgagors the right to redeem their property following default for a statutorily set period of time. This paper develops a theory that explains these laws as a means of protecting landowners against the loss of nontransferable values associated with their land. A longer redemption period reduces the risk that this value will be lost but also increases the likelihood of default. The optimal redemption period balances these effects. Empirical analysis of cross-state data from the early twentieth century suggests that these factors, in combination with political considerations, explain the existence and length of redemption laws.

Fair Housing Enforcement and Changes in Discrimination between 1989 and 2000: An Exploratory Study

Using paired testing data from the 1989 and 2000 Housing Discrimination Studies (HDS) and data on fair housing enforcement activities during the 1990s in the corresponding metro areas, we investigate whether 1989-2000 changes in the metropolitan incidence of racial/ethnic discrimination correlate with fair housing enforcement activity during the 1990s. We found that higher amounts of state and local enforcement activity supported by HUD through its FHIP and FHAP programs (especially the amount of dollars awarded by the courts) were consistently associated with greater declines in discrimination against black apartment-seekers and home-seekers. The evidence does not support similar conclusions for housing market discrimination against Hispanics where the level of enforcement is much lower.

Discrimination in Metropolitan Housing Markets Phase II: Asians and Pacific Islanders

This report documents the results of a an 11-city paired testing study by the Department of Housing and Urban Development of housing discrimination against Asian- Americans and Pacific Islanders. The study shows that one out of every five Asians and Pacific Islanders attempting to buy or rent a home are discriminated against, a rate similar to that of African Americans and Hispanics.

Discrimination in Metropolitan Housing Markets: National Results from Phase 1 of the Housing Discrimination Study (HDS)

The Housing Discrimination Study 2000 (HDS 2000) is the third nationwide effort sponsored by HUD to measure the amount of discrimination faced by minority home seekers. This report provides national estimates of discrimination faced by African Americans and Hispanics in 2000 as they searched for housing in the sales and rental markets. It also provides an accurate measure of how housing discrimination has changed since 1989. The report shows large decreases between 1989 and 2000 in the level of discrimination experienced by Hispanics and African Americans seeking to a buy a home. There are, however, worrisome upward trends of discrimination in the areas of geographic steering in home sales for African Americans and the amount of help agents provide to Hispanics with obtaining financing. There has also been a modest decrease in discrimination toward African Americans seeking to rent a unit. This downward trend, however, has not been seen for Hispanic renters. Hispanic renters now are more likely to experience discrimination in their housing search than do African American renters.

What Is Known about Testing for Discrimination: Lessons Learned by Comparing across Different Markets

The paper provides a fairly comprehensive examination of recent empirical work on discrimination within economics. The three major analytical approaches considered are traditional regression analysis of outcomes, paired testing or audits, and finally analysis of performance where higher group performance suggests that a group has been treated disfavorably. The review covers research in the labor, credit, and consumption markets, as well as recent studies of discrimination within the legal system. The review suggests that the validity of interpreting observed racial differences as discrimination depends heavily on whether the analysis is based on a sample that is representative of a population of individuals or households or based on a sample of market transactions, as well as the analyst?s ability to control for heterogeneity within that sample. Heterogeneous firm behavior and differentiated products, such as those found in labor and housing markets, also can confound empirical analyses of discrimination by confusing the allocation of individuals across firms or products with disparate treatment or by ignoring disparate impacts that might arise based on that allocation.

Discrimination in Metropolitan Housing Markets: Phase 3 - Native Americans

This paper documents the results of a pilot paired testing program to examine the treatment of Native Americans by real estate agents in rental housing markets in three states and owner-occupied housing markets in one state. The study finds that the level of discrimination experienced by Native Americans in rental markets exceed those experienced by Hispanics, Blacks, and Asian-Americans.

Measurement of isotopic uranium in water for compliance monitoring by liquid scintillation counting with alpha/beta discrimination

A simple and inexpensive method is described for analysis of uranium (U) activity and mass in water by liquid scintillation counting using $\alpha$/$\beta$ discrimination. This method appears to offer a solution to the need for an inexpensive protocol for monitoring U activity and mass simultaneously and an alternative to the potential inaccuracy involved when depending on the mass-to-activity conversion factor or activity screen.^ U is extracted virtually quantitatively into 20 ml extractive scintillator from a 1-$\ell$ aliquot of water acidified to less than pH 2. After phase separation, the sample is counted for a 20-minute screening count with a minimum detection level of 0.27 pCi $\ell\sp{-1}$. $\alpha$-particle emissions from the extracted U are counted with close to 100% efficiency with a Beckman LS6000 LL liquid scintillation counter equipped with pulse-shape discrimination electronics. Samples with activities higher than 10 pCi $\ell\sp-1$ are recounted for 500-1000 minutes for isotopic analysis. Isotopic analysis uses events that are automatically stored in spectral files and transferred to a computer during assay. The data can be transferred to a commercially available spreadsheet and retrieved for examination or data manipulation. Values for three readily observable spectral features can be rapidly identified by data examination and substituted into a simple formula to obtain $\sp{234}$U/$\sp{238}$U ratio for most samples. U mass is calculated by substituting the isotopic ratio value into a simple equation.^ The utility of this method for the proposed compliance monitoring of U in public drinking water supplies was field tested with a survey of drinking water from Texas supplies that had previously been known to contain elevated levels of gross $\alpha$ activity. U concentrations in 32 samples from 27 drinking water supplies ranged from 0.26 to 65.5 pCi $\ell\sp{-1}$, with seven samples exceeding the proposed Maximum Contaminant Level of 20 $\mu$g $\ell\sp{-1}$. Four exceeded the proposed activity screening level of 30 pCi $\ell\sp{-1}$. Isotopic ratios ranged from 0.87 to 41.8, while one sample contained $\sp{234}$U activity of 34.6 pCi $\ell\sp{-1}$ in the complete absence of its parent, $\sp{238}$U. U mass in the samples with elevated activity ranged from 0.0 to 103 $\mu$g $\ell\sp{-1}$. A limited test of screening surface and groundwaters for contamination by U from waste sites and natural processes was also successful. ^