Visually guided vergence in a new stereo camera system

People move their eyes several times each second, to selectivelyanalyze visual information from specific locations. This is impor-tant, because analyzing the whole scene in foveal detail would re-quire a beachball-sized brain and thousands of additional caloriesper day. As artificial vision becomes more sophisticated, it mayface analogous constraints. Anticipating this, we previously devel-oped a robotic head with biologically realistic oculomotor capabil-ities. Here we present a system for accurately orienting the cam-eras toward a three-dimensional point. The robot’s cameras con-verge when looking at something nearby, so each camera shouldideally centre the same visual feature. At the end of a saccade,we combine priors with cross-correlation of the images from eachcamera to iteratively fine-tune their alignment, and we use the ori-entations to set focus distance. This system allows the robot toaccurately view a visual target with both eyes

Choosing Poorly: Reward-Induced Strategy Shifts in Estimating the Probabilitiesof Conjunctions and Disjunctions

Human estimates of the probabilities of combinations of events show well-established violations of probabilitytheory, most notably the conjunction and disjunction fallacies. These violations have led researchers to conclude that therules of probability are too complex for most people to use, and that cognitively-easier approximations such as averagingare used instead. Unlike previous work that has assumed that individuals use only a single combination rule, we collectedrepeated estimates of conjunctions and disjunctions and investigated whether individuals consistently used a single rule orused a repertoire of rules in a trial-by-trial Bayesian analysis. When not incentivized, most participants were best describedas randomly selecting a combination rule on each trial, and the correct rule was the most often used. Despite this, whenincentivized to use their single-best strategy participants were more likely to use the incorrect averaging rule. People do notseem to understand their own strategies well

Investing in Mobility: Freight Transport in the Hudson Region

Proposes a framework for assessing alternative investments in freight rail, highway, and transit capacity that would increase the ability to improve mobility and air quality in the New York metropolitan area

Results from the High-Z Supernova Search Team

We review the use of Type Ia supernovae for cosmological distance determinations. Low-redshift SNe Ia ($z \lesssim 0.1$) demonstrate that (a) the Hubble expansion is linear, (b) $H_0 = 65 \pm 2$ (statistical) km s$^{-1}$ Mpc$^{-1}$, (c) the bulk motion of the Local Group is consistent with the COBE result, and (d) the properties of dust in other galaxies are similar to those of dust in the Milky Way. We find that the light curves of high-redshift SNe Ia are stretched in a manner consistent with the expansion of space; similarly, their spectra exhibit slower temporal evolution (by a factor of $1 + z$) than those of nearby SNe Ia. The luminosity distances of our 16 high-redshift SNe Ia are, on average, 10--15% farther than expected in a low mass-density ($\Omega_M=0.2$) universe without a cosmological constant. Our analysis strongly supports eternally expanding models with positive cosmological constant and a current acceleration of the expansion. We address many potential sources of systematic error; at present, none of them reconciles the data with $\Omega_\Lambda=0$ and $q_0 \geq 0$. The dynamical age of the Universe is estimated to be $14.2 \pm 1.7$ Gyr, consistent with the ages of globular star clusters.Comment: 17 pages, latex, plus 2 figures, to appear in the Proceedings of the 3rd International Symposium on Sources and Detection of Dark Matter in the Universe (DM98), Feb. 1998, ed. D. Clin

The Case for an Accelerating Universe from Supernovae

The unexpected faintness of high-redshift Type Ia supernovae (SNe Ia), as measured by two teams, has been interpreted as evidence that the expansion of the Universe is accelerating. We review the current challenges to this interpretation and seek to answer whether the cosmological implications are compelling. We discuss future observations of SNe Ia which could offer extraordinary evidence to test acceleration.Comment: To appear as an Invited Review for PASP 20 pages, 13 figure

Conclusive Evidence of Replication of a Plant Virus in Honeybees Is Lacking

The recent article by Li et al. (1) lacks adequate evidence to support the authors’ assertion that a plant virus propagates or replicates in honeybees. Instead, it is possible that tobacco ringspot virus (TRSV) virions associate with the honeybee and parasitic Varroa mites in the absence of TRSV replication

Multiple strategies in conjunction and disjunction judgments : most people are normative part of the time

Do people use a single strategy or sample from multiple strategies when estimating the conjunction and disjunction of two independent events? Here we address this tension directly by comparing individual level Bayesian simulations of multi and single strategy models using data from a frequency estimation experiment. Participants were shown two statements describing attributes and asked to estimate how many people had either one attribute, conjunction, or disjunction of attributes. In our Bayesian simulations we compare models in which participants either adopt a single strategy or sample from a set of strategies when forming estimates of both conjunctions and disjunctions. We compared every permutation of models in which a participant is responding based on a single component, a weighted average of the two events, probability theory, or combination of strategies. Our findings show that people sample from multiple strategies and are sampling from the normative strategy some of the time