3,548 research outputs found
Adobe Flash as a medium for online experimentation: a test of reaction time measurement capabilities
Adobe Flash can be used to run complex psychological experiments over the Web. We examined the reliability of using Flash to measure reaction times (RTs) using a simple binary-choice task implemented both in Flash and in a Linux-based system known to record RTs with millisecond accuracy. Twenty-four participants were tested in the laboratory using both implementations; they also completed the Flash version on computers of their own choice outside the lab. RTs from the trials run on Flash outside the lab were approximately 20 msec slower than those from trials run on Flash in the lab, which in turn were approximately 10 msec slower than RTs from the trials run on the Linux-based system (baseline condition). RT SDs were similar in all conditions, suggesting that although Flash may overestimate RTs slightly, it does not appear to add significant noise to the data recorded
Using Adobe Flash Lite on mobile phones for psychological research: reaction time measurement reliability and inter-device variability
Mobile telephones have significant potential for use in psychological research, possessing unique characteristics—not least their ubiquity—that may make them useful tools for psychologists. We examined whether it is possible to measure reaction times (RTs) accurately using Adobe Flash Lite on mobile phones. We ran simple and choice RT experiments on two widely available mobile phones, a Nokia 6110 Navigator and a Sony Ericsson W810i, using a wireless application protocol (WAP) connection to access the Internet from the devices. RTs were compared within subjects with those obtained using a Linux-based millisecond-accurate measurement system. Results show that measured RTs were significantly longer on mobile devices, and that overall RTs and distribution of RTs varied across device
Prospect relativity: How choice options influence decision under risk
In many theories of decision under risk (e.g., expected utility theory, rank-dependent utility theory, and prospect theory), the utility of a prospect is independent of other options in the choice set. The experiments presented here show a large effect of the available options, suggesting instead that prospects are valued relative to one another. The judged certainty equivalent for a prospect is strongly influenced by the options available. Similarly, the selection of a preferred prospect is strongly influenced by the prospects available, Alternative theories of decision under risk (e.g., the stochastic difference model, multialternative decision field theory, and range frequency theory), where prospects are valued relative to one another, can provide an account of these context effects
The QSO evolution derived from the HBQS and other complete QSO surveys
An ESO Key programme dedicated to an Homogeneous Bright QSO Survey (HBQS) has
been completed. 327 QSOs (Mb<-23, 0.3<z<2.2) have been selected over 555 deg^2
with 15<B<18.75. For B<16.4 the QSO surface density turns out to be a factor
2.2 higher than what measured by the PG survey, corresponding to a surface
density of 0.013+/-.006 deg^{-2}. If the Edinburgh QSO Survey is included, an
overdensity of a factor 2.5 is observed, corresponding to a density of
0.016+/-0.005 deg^{-2}. In order to derive the QSO optical luminosity function
(LF) we used Monte Carlo simulations that take into account of the selection
criteria, photometric errors and QSO spectral slope distribution. The LF can be
represented with a Pure Luminosity Evolution (L(z)\propto(1+z)^k) of a two
power law both for q_0=0.5 and q_0=0.1. For q_0=0.5 k=3.26, slower than the
previous Boyle's (1992) estimations of k=3.45. A flatter slope beta=-3.72 of
the bright part of the LF is also required. The observed overdensity of bright
QSOs is concentrated at z<0.6. It results that in the range 0.3<z<0.6 the
luminosity function is flatter than observed at higher redshifts. In this
redshift range, for Mb<-25, 32 QSOs are observed instead of 19 expected from
our best-fit PLE model. This feature requires a luminosity dependent luminosity
evolution in order to satisfactorily represent the data in the whole 0.3<z<2.2
interval.Comment: Invited talk in "Wide Field Spectroscopy" (20-24 May 1996, Athens),
eds. M. Kontizas et al. 6 pages and 3 eps figures, LaTex file, uses epfs.sty
and crckapb.sty (included
Static Critical Behavior of the Spin-Freezing Transition in the Geometrically Frustrated Pyrochlore Antiferromagnet Y2Mo2O7
Some frustrated pyrochlore antiferromagnets, such as Y2Mo2O7, show a
spin-freezing transition and magnetic irreversibilities below a temperature Tf
similar to what is observed nonlinear magnetization measurements on Y2Mo2O7
that provide strong evidence that there is an underlying thermodynamic phase
transition at Tf, which is characterized by critical exponents \gamma \approx
2.8 and \beta \approx 0.8. These values are typical of those found in random
spin glasses, despite the fact that the level of random disorder in Y2Mo2O7 is
immeasurably small.Comment: Latex file, calls for 4 encapsulated postscript figures (included).
Submitted to Phys. Rev. Letters
The baryon density at z=0.9-1.9 - Tracing the warm-hot intergalactic medium with broad Lyman alpha absorption
We present an analysis of the Lyman alpha forests of five quasar spectra in
the near UV. Properties of the intergalactic medium (IGM) at an intermediate
redshift interval (0.9 < z < 1.9) are studied. The amount of baryons in the
diffuse photoionised IGM and the warm-hot intergalactic medium (WHIM) are
traced to get constraints on the redshift evolution of the different phases of
the intergalactic gas. The baryon density of the diffuse IGM is determined with
photoionisation calculations under the assumption of local hydrostatic
equilibrium. We assume that the gas is ionised by a metagalactic background
radiation with a Haardt & Madau (2001) spectrum. The WHIM is traced with broad
Lyman alpha (BLA) absorption. The properties of a number of BLA detections are
studied. Under the assumption of collisional ionisation equilibrium a lower
limit to the baryon density could be estimated. It is found that the diffuse
photoionised IGM contains at least 25% of the total baryonic matter at
redshifts 1 < z < 2. For the WHIM a lower limit of 2.4% could be determined.
Furthermore the data indicates that the intergalactic gas is in a state of
evolution at z=1.5. We confirm that a considerable part of the WHIM is created
between z=1 and z=2.Comment: 6 pages, 1 figure, accepted for publication in A&
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Trend Damping: Under-Adjustment, Experimental Artifact, or Adaptation to Features of the Natural Environment?
People’s forecasts from time series underestimate future values for upward trends and overestimate them for downward ones. This trend damping may occur because 1) people anchor on the last data point and make insufficient adjustment to take the trend into account, 2) they adjust towards the average of the trends they have encountered within the experiment, or 3) they are adapted to an environment in which natural trends tend to be damped. Two experiments eliminated the first account: for series that are negatively accelerated or have shallow slopes, people showed anti-damping (the opposite of damping), a phenomenon that cannot be interpreted in terms of under-adjustment. These experiments also produced results consistent with the second account: forecasts for a given function clearly depended on the other functions that were forecast within the same experiment. However, this second account was itself eliminated by a third experiment demonstrating both damping and, to a lesser degree, anti-damping when people forecast from a single series. We conclude that people have adapted to degrees of growth and decay that are representative of their environment: damping occurs when trends in presented series are steeper than this and anti-damping occurs when they are shallower
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