Learning to perceive object unity: a connectionist account

To explore questions of how human infants begin to perceive partly occluded objects, we devised two connectionist models of perceptual development. The models were endowed with an existing ability to detect several kinds of visual information that have been found important in infants’ and adults’ perception of object unity (motion, co‐motion, common motion, relatability, parallelism, texture and T‐junctions). They were then presented with stimuli consisting of either one or two objects and an occluding screen. The models’ task was to determine whether the object or objects were joined when such a percept was ambiguous, after specified amounts of training with events in which a subset of possible visual information was provided. The model that was trained in an enriched environment achieved superior levels of performance and was able to generalize veridical percepts to a wide range of novel stimuli. Implications for perceptual development in humans, current theories of development and origins of knowledge are discussed.     

The Role of Formal Mentoring on Business Success and Self-Esteem in Participants of a New Business Start-Up Program

The current study investigated the relationship between career-related mentoring, psychosocial mentoring, business success, and self-esteem in participants of a program that was designed to assist in the establishment of a new business. Seventy-seven protégés and their matched mentors were included in the study. A comparison of mentor and protégé perceptions revealed that mentors considered themselves to provide higher levels of psychosocial support than did the protégés. Protégé perceptions of business success were predicted by the frequency of mentor contact and the level of career-related support provided by their mentor.     

Choice preferences without inferences: subconscious priming of risk attitudes

We present a procedure for subconscious priming of risk attitudes. In Experiment 1, we were reliably able to induce risk‐seeking or risk‐averse preferences across a range of decision scenarios using this priming procedure. In Experiment 2, we showed that these priming effects can be reversed by drawing participants' attention to the priming event. Our results support claims that the formation of risk preferences can be based on preconscious processing, as for example postulated by the affective primacy hypothesis, rather than rely on deliberative mental operations, as posited by several current models of judgment and decision making. Copyright © 2002 John Wiley & Sons, Ltd.     

Reliability and Validity of the Complex Postformal Thought Questionnaire: Assessing Adults’ Cognitive Development

Three studies investigated the psychometric properties of the complex postformal thought (PFT) questionnaire (Sinnott, unpublished scale, 1998; Sinnott and Johnson 1997), which is a measure of adult cognitive development. The scale was found to be moderately reliable (α = .63). To assess construct validity, a comparison of participants’ performance on the PFT scale to their performance on the Need for Cognition scale was conducted, which indicated the PFT scale is valid measure of complex thought. Factor analysis reduced the scale to three factors, which correspond to important components of PFT: Multiple Elements, Subjective Choice, and Underlying Complexities. Implications for understanding the nature of adult cognitive development and the usefulness of this new measure for research in this area are discussed.     

Nearly unbiased estimators for the three‐parameter Weibull distribution with greater efficiency than the iterative likelihood method

The maximum likelihood estimation (MLE) method is the most commonly used method to estimate the parameters of the three‐parameter Weibull distribution. However, it returns biased estimates. In this paper, we show how to calculate weights which cancel the biases contained in the MLE equations. The exact weights can be computed when the population parameters are known and the expected weights when they are not. Two of the three weights' expected values are dependent only on the sample size, whereas the third also depends on the population shape parameters. Monte Carlo simulations demonstrate the practicability of the weighted MLE method. When compared with the iterative MLE technique, the bias is reduced by a factor of 7 (irrespective of the sample size) and the variability of the parameter estimates is also reduced by a factor of 7 for very small sample sizes, but this gain disappears for large sample sizes.     

Coherence and Truth: A Cognitive Model of Propositional Truth Attribution

The truth value assigned to a proposition is treated by philosophers, logicians, and most psychologists as an abstract construct, a theoretical object outside the cognitive system. Breaking away from this consensus, we propose to carry out a psychological investigation to analyse the objective, verifiable properties of representations categorized as true by human individuals. We shall reject the conception whereby attributing a truth value to a proposition is the result of the activation of knowledge about the truth of that proposition. We shall also exclude the conception of truth as the result of the establishment of a correspondence with the world. We propose that truth be understood as the result of a decision about the values taken on by the conditions for fulfilment of the act of referencing in a mental model. Our cognitive model of propositional truth attribution is built on the assumption that the truth value of a proposition is determined by the ability of that proposition to fit into the theory of the field to which it refers. This attribution is viewed as a two-stage cognitive activity. During the first stage, the features defining the coherence of the proposition in the activated mental model determine its plausibility value. This defines a generally inconsistent set of truth candidates. The second stage involves selecting the subset containing all propositions which, in context, will be considered true. Two selection criteria are used: maximum consistency and connectivity. The preliminary experimental results proved to be compatible with the proposed model.     

Rats respond for food in the presence of free food: How free is the “free” food?

An experiment conducted by A.J. Neuringer (Science, 1969,166, 399–401) in which he reported that rats maintained appreciable levels of bar pressing for earned food in the presence of freely available food was critically examined and replicated. Rats were trained to bar press, then housed in operant chambers and administered a 15-day preference test between free and earned food, followed successively by 10 days of free food only, a second 6-day preference test, and 7 days of earned food only. Throughout the experiment half of the animals were provided with tall free-food containers similar to those used by Neuringer; the other half were provided with short containers similar to those more commonly employed by other researchers. The former animals showed a consistent propensity to bar press for earned food across both preference tests, while the latter animals showed only an initial propensity to bar press which subsequently declined to very low levels. These results indicate that the maintenance of significant amounts of bar pressing by the rats in Neuringer's report was due to the relatively more effortful free-food source he employed. The utility of a neophobia-optimality model in explaining the present data is discussed.