Effective random seeding of random number generators

To obtain different sequences of values from a random number generating algorithm, we must start with different seed values or discard a variable number of initial samples. For maximum independence among sequences, differences must include the lowest order seed bits, and some generators require one to wait many samples for differences to propagate to the significant bits. While it is straightforward to generate two statistically independent sequences, it is surprisingly difficult to generate three or more such sequences.     

An exact probability distribution on the connectivity of random graphs

Recently, several authors have proposed the use of random graph theory to evaluate the adequacy of cluster analysis results. One such statistic is the minimum number of lines (edges) V needed to connect a random graph. Erdös and Rényi derived asymptotic distributions of V. Schultz and Hubert showed in a Monte Carlo study that the asymptotic approximations are poor for small sample sizes n typically used in data analysis applications. In this paper the exact probability distribution of V is given and the distributions for some values of n are tabulated and compared with existing Monte Carlo approximations.     

Modeling patterns of probability calibration with random support theory: Diagnosing case-based judgment

We describe four broad characterizations of subjective probability calibration (overconfidence, conservatism, ecologically perfect calibration, and case-based judgment) and show how Random Support Theory (RST) can serve as a tool for representing, evaluating, and discriminating between these perspectives. We present five studies of probability judgment in a simulated stock market setting and analyse the calibration data in terms of RST parameters. The observed pattern of calibration varies with the outcome base rate and cue value diagnosticity, as predicted by case-based judgment. A similar pattern of calibration is found in real-world judgments of experts in various domains. Case-based RST—defined as RST with stable parameter values—provides a parsimonious account of the substantial changes in calibration performance observed across different judgment environments.     

Studies in subjective probability l: Prediction of random events

When students are asked to predict the outcome of a random event, where all alternatives are equally probable (lotteries), they tend to choose central, "representative" values, and avoid extreme ones. In ten informal experiments, it is shown how this pattern of choices is influenced by various procedural and structural changes in the basic task. The results show that guessing behavior can be described as a kind of absolute judgment, subject to grouping, anchoring and context effects. Of the two general prediction heuristics originally proposed by Kahneman & Tversky (1973), "representativeness" applies better than "availability". In fact, a major strategy of guessing is apparently to eschew numbers with prominent, "non-random" properties, which at the same time are highly available to the subjects.     

The assessment of subjective probability distributions: A training experiment

For this experiment 22 Ss were especially trained to assess subjective probability distributions for proportions concerning student characteristics. Two different assessment techniques were used. There were four experimental sessions. From the second session on, Ss received feedback about their performance in the previous session(s). While Ss' associated by far too much confidence with their assessments at the beginning, they learned to assess more realistic distributions. Furthermore, discrepancies between techniques were reduced.Some considerations for a more effective training procedure are made and the concept of giving feedback only according to the tightness of the assessed distribution is critically discussed.     

Making heads turn: the effect of familiarity and stimulus rotation on a gender-classification task

Recent work has demonstrated that facial familiarity can moderate the influence of inversion when completing a configural processing task. Here, we examine whether familiarity interacts with intermediate angles of orientation in the same way that it interacts with inversion. Participants were asked to make a gender classification to familiar and unfamiliar faces shown at seven angles of orientation. Speed and accuracy of performance were assessed for stimuli presented (i) as whole faces and (ii) as internal features. When presented as whole faces, the task was easy, as revealed by ceiling levels of accuracy and no effect of familiarity or angle of rotation on response times. However, when stimuli were presented as internal features, an influence of facial familiarity was evident. Unfamiliar faces showed no increase in difficulty across angle of rotation, whereas familiar faces showed a marked increase in difficulty across angle, which was explained by significant linear and cubic trends in the data. Results were interpreted in terms of the benefit gained from a mental representation when face processing was impaired by stimulus rotation.     

Recognising faces seen alone or with others: when two heads are worse than one

There is a large body of work investigating face identification, but most of this addresses recognition of a single person. Here, we examine how recognition is affected by the presence of a second face. In Experiments 1 and 2, we demonstrate that memory for an unfamiliar face is severely reduced if it is seen alongside a second person. Sequential presentation of two target faces further reduces accuracy. In Experiments 3 and 4, we demonstrate the same disadvantage for two‐face targets in a matching task, where subjects have no time limits or memory requirement. In matching, the damaging effect of a second face is greatest when the targets are placed close together. Furthermore, there is a general advantage for faces presented to the left. We suggest that it may not be possible to extrapolate results from single‐face studies to experiments (or realistic situations) involving more than one person. Copyright © 2006 John Wiley & Sons, Ltd.     

Making probability judgments of future product failures: The role of mental unpacking

When consumers mentally unpack (i.e., imagine) the reasons for product failure, their probability judgments of future product failures are higher than when no mental unpacking is undertaken. However, increasing the level of mental unpacking does not lead to monotonically increasing effects on probability judgments but results in inverted U-shaped relationships. Using a two-factor structure, we propose that when consumers undertake mental unpacking, there will be two conflicting processes; while imagining causes for an event will lead to greater perceived probability, the greater difficulty in generating reasons for an event will lead to lower perceived probability.     

A microprocessor-based real-time BASIC random interstimulus interval generator with different probability density functions

A low-cost random interstimulus interval (ISI) generator with different probability density functions is described. The frequency histograms of the output ISIs are uniformly, normally, exponentially, and binary distributed functions.     

An experiment with occasional false information

An experiment is described in which subjects were presented, under one condition, with advance information of doubtful value. The evidence suggests that advance information was accepted, although the uncertainty created had a detrimental effect on the subjects' performance.     

An inexpensive experiment controller for stand-alone applications or distributed processing networks

An inexpensive microprocessor-based experiment controller available as a commercially produced bare printed circuit board is described. It provides for up to 8 inputs and 40 outputs. An 8K Experiment Control BASIC (ECBASIC) and a compiled Experiment Control Language (ECL) are also available. Both languages have internal structures that enable time and responses to be dealt with in a very convenient and error-free manner. Time and response count are automatically incrementing variables that need only to be tested by the user program. ECBASIC provides a 10-msec accuracy, whereas ECL provides a l-msec accuracy. ECL provides extensive support for event-driven programs. The board and software are designed to provide an orderly migration from a stand-alone controller running ECBASIC as a relay-rack replacement, to a network of ECBASIC machines on a small computer, to a true error-checking network of ECL machines on a time-sharing operating system of a large computer. Network communication is over the three wires of a single unmodified RS232 asynchronous serial communication line.     

The random effects prep continues to mispredict the probability of replication

In their reply, Lecoutre and Killeen (2010) argue for a random effects version of p_rep, in which the observed effect from one experiment is used to predict the probability that an effect from a different but related experiment will have the same sign. They present a figure giving the impression that this version of p_rep accurately predicts the probability of replication. We show that their results are incorrect and conceptually limited, even when corrected. We then present a meaningful evaluation of the random effects p_rep as a predictor and find that, as with the fixed effects p_rep, it performs very poorly.     

Conditional probability and components of rt in the variable foreperiod experiment

If the passage of time during the foreperiod in a variable foreperiod experiment is marked by a series of tones, RT decreases with the conditional probability of stimulus occurrence. RTs at short foreperiods, however, are rather slower than would be expected on the basis of a simple conditional probability effect. It is suggested that this is attributable to an independent “initial slow reaction” effect, and it is shown that the degree of this effect is influenced by the duration of the prior foreperiod. The results are related to those of variable foreperiod a-reactions in which no conditional probability effect has been found, and it is argued that in a marked reaction of the kind described above, the initial slow reaction effect behaves like an a-reaction component of RT. It is suggested that the absence of a conditional probability effect in the a-reaction and its presence in the marked reaction are related to the fact that a different type of sensory process is used to identify the signal in each case.     

Authorship Decision Making: An Empirical Investigation

This empirical study concerns the authorship credit decision-making processes and outcomes that occur among coauthors in cases of multiauthored publications. The 2002 American Psychological Association (APA) Ethics Code offers standards for determining authorship order; however, little is known about how these decisions are made in actual practice. Results from a survey of 109 randomly selected authors indicated that most authors were satisfied with the decision-making process and outcome with few disagreements. Participants reported cases of both undeserved authorship being given and omission of deserving contributors' names as coauthors. Some factors associated with authorship decisions included “sense of loyalty or obligation,” “publish or perish pressures,” and “power differentials.” Authors who used APA standards were significantly more satisfied with both the process and outcome of authorship credit decisions.     

An analysis of indefinite probability statements

An analysis of indefinite probability statements has been offered by Jackson and Pargetter (1973). We accept that this analysis will assign the correct probability values for indefinite probability claims. But it does so in a way which fails to reflect the epistemic state of a person who makes such a claim. We offer two alternative analyses: one employing de re (epistemic) probabilities, and the other employing de dicto (epistemic) probabilities. These two analyses appeal only to probabilities which are accessible to a person who makes an indefinite probability judgment, and yet we prove that the probabilities which either of them assigns will always be equivalent to those assigned by the Jackson and Pargetter analysis.     

An analysis of random and systematic changes with practice

Six motor tests and six nonverbal tests were administered four times to the same subjects. Subjective reports of the subjects are discussed, changes in mean scores and in variability and score correlations from trial to trial are surveyed, and factor analyses of results on the first and fourth trials are presented and compared. Implications of the findings with respect to correction for attenuation are pointed out.Thanks are due to Mr. Searles and his staff at the Henry Ford Trade School, who gave both suggestions and aid in completing this work; to Dr. L. L. Thurstone, who gave suggestions for certain aspects of the analysis; and to L. R. Tucker and Robert Blakey, who made the final factorial analyses and suggested various conclusions.     

Taste-aversion retention: An animal experiment with implications for consummatory-aversion alcoholism treatments

Inquiries into the longevity of illness-induced aversions (TAs) in animals are relevant to consummatory-aversion (CA) treatments of human alcoholism. The range of nausea reactions that accompanied the relapses of some alcoholics who had acquired alcohol aversions during covertsensitization (verbal aversion) alcoholism treatment has implicated CA forgetting as one probable contributor to recidivism. CA forgetting is operationalized as aversion diminution during postconditioning periods in which Ss abstain from contact with the target substance. TAs of varying strengths were induced in groups of Sprague-Dawley rats that received low, medium or high doses of the illness-inducing drug cyclophosphamide following saccharin-solution ingestion. TA retention was assessed following saccharin-free intervals of 2–40 days. Each Ss' retention interval was followed by 30 days of two-bottle preference testing, thereby additionally permitting an assessment of TA extinction following differing degrees of TA forgetting. Low-dose Ss displayed moderate strength TAs that were forgotten within 20 days and that had little resistance to extinction when testing began shortly after conditioning. Medium-dose Ss displayed stronger TAs having greater resistance to both forgetting and extinction. Unlike these low- and medium-dose TAs, high-dose TAs were impervious to aversion degradation as a result of forgetting. This finding is interpreted as supporting the attempted induction of intense nausea during covert-sensitization and chemical aversion (emetic therapy) alcoholism treatment. Other related conditioning procedures that may contribute to effective treatment are also discussed.     

Clear heads are cool heads: Emotional clarity and the down-regulation of antisocial affect

Emotional clarity results in reduced anger, but it is important to better understand why this is true. Drawing upon existing cybernetic models of affect regulation, the authors propose that affect down-regulation operations are crucial to understanding the clarity/anger relationship. A two study, multi-method investigation provided support for these hypotheses. Study 1 used dispositional measures of emotional clarity, anger control, and trait anger, and found that anger control mediated the relationship between clarity and reduced anger. Study 2 found that individuals high in emotional clarity were successful in correcting for the influence of aggressive primes on subsequent evaluations. Importantly, though, disrupting these affect regulation operations through the imposition of cognitive load left emotionally clear individuals as susceptible to antisocial affect priming as emotionally unclear individuals. In total, the studies suggest that emotional clarity is closely associated with the effortful down-regulation of antisocial affect.