14,016 research outputs found
Political Orientation and the Decision to Major in Economics: Some Preliminary Observations
Studies find that students major in economics for a variety of reasons. None, however, have examined students' political orientations as a possible factor in their choice of majors. Economics, as compared to other social sciences, tends to produce conservative policy recommendations. This pilot study explores whether more conservative students are attracted to economics. Our study found that men with conservative political leanings are more likely to major in economics and that male students in economics are more conservative than female students. Political orientation, however, does not appear to be a significant factor in the choice of a major for women.
Age-Related Differences in Auditory Processing as Assessed by Amplitude-Modulation Following Responses in Quiet and in Noise
Our knowledge of age-related changes in auditory processing in the central auditory system is limited, unlike the changes in the peripheral hearing organs which are more extensively studied. This study aims to further understanding of temporal processing in aging using non-invasive electrophysiological measurements in a rat model system. Amplitude modulation following responses (AMFRs) were assessed using sinusoidally amplitude modulated (SAM) tones presented to aged (92- to 95-weeks old) and young (9- to 12-weeks old) Fischer-344 rats. The modulation frequency and sound level were systematically varied, and the SAM stimuli were also presented simultaneously with wideband background noise at various levels. The overall shapes and cutoff frequencies of the AMFR temporal modulation transfer functions (tMTFs) were similar between young and aged animals. The fast Fourier transform (FFT) amplitudes of the aged animals were similar to the young in the 181–512 Hz modulation frequency range, but were significantly lower at most modulation frequencies above and below. There were no significant age-related differences in the nature of growth or FFT amplitudes with change in sound level at 256 and 1024 Hz modulation frequencies. The AMFR amplitudes were also not correlated with the ABR wave I or wave III amplitudes elicited for broadband click stimuli presented at the same sound level suggesting that sustained AMFR provide complementary information to phasic ABR responses. The FFT amplitudes varied significantly between young and aged animals for SAM stimuli in the presence of background noise, depending on the modulation frequency used and signal to noise ratio. The results show that the representation of temporally modulated stimuli is similar between young and aged animals in quiet listening conditions, but diverges substantially with the addition of background noise. This is consistent with a decrease in inhibition causing altered temporal processing with age
Benign overfitting in ridge regression
Classical learning theory suggests that strong regularization is needed to
learn a class with large complexity. This intuition is in contrast with the
modern practice of machine learning, in particular learning neural networks,
where the number of parameters often exceeds the number of data points. It has
been observed empirically that such overparametrized models can show good
generalization performance even if trained with vanishing or negative
regularization. The aim of this work is to understand theoretically how this
effect can occur, by studying the setting of ridge regression. We provide
non-asymptotic generalization bounds for overparametrized ridge regression that
depend on the arbitrary covariance structure of the data, and show that those
bounds are tight for a range of regularization parameter values. To our
knowledge this is the first work that studies overparametrized ridge regression
in such a general setting. We identify when small or negative regularization is
sufficient for obtaining small generalization error. On the technical side, our
bounds only require the data vectors to be i.i.d. sub-gaussian, while most
previous work assumes independence of the components of those vectors.Comment: 28 page
Some Remarks on the Question of Charge Densities in Stationary-Current-Carrying Conductors
Recently, some discussions arose as to the definition of charge and the value
of the density of charge in stationary-current-carrying conductors. We stress
that the problem of charge definition comes from a misunderstanding of the
usual definition. We provide some theoretical elements which suggest that
positive and negative charge densities are equal in the frame of the positive
ions.Comment: 14 pages, TeX, macro newsym.tex include
The Barrier Method: A Technique for Calculating Very Long Transition Times
In many dynamical systems there is a large separation of time scales between
typical events and "rare" events which can be the cases of interest. Rare-event
rates are quite difficult to compute numerically, but they are of considerable
practical importance in many fields: for example transition times in chemical
physics and extinction times in epidemiology can be very long, but are quite
important. We present a very fast numerical technique that can be used to find
long transition times (very small rates) in low-dimensional systems, even if
they lack detailed balance. We illustrate the method for a bistable
non-equilibrium system introduced by Maier and Stein and a two-dimensional (in
parameter space) epidemiology model.Comment: 20 pages, 8 figure
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