Test of a distributional theory of intuitive numerical prediction

This paper investigates models that describe how subjects combine uncertain information to arrive at an intuitive prediction of a criterion. Subjects were trained, with feedback, to predict a numerical criterion from each of three single cues. Then they were asked to predict the criterion, without feedback, either from pairs of cues or from single cues. Their predictions were not consistent with a relative weight averaging model, since pairs of cues did not combine additively. Instead, the effect of a cue was inversely proportional to the standard deviation of the criterion at each level of the cue. Subjects appeared to apply greater weight to cue levels with smaller variance, i.e., those cue levels that were more valid. The data could be described by a distributional theory referred to as the equal probability model. For the present experiment, this model implies that the criterion means associated with the levels of each cue are weighted by the reciprocals of the standard deviations and then averaged. Relations between the equal probability model and other models of impression formation are discussed.     

The ABCs of categorical perception

Studies of speech perception first revealed a surprising discontinuity in the way in which stimulus values on a physical continuum are perceived. Data which demonstrate the effect in nonspeech modes have challenged the contention that categorical perception is a hallmark of the speech mode, but the psychophysical models that have been proposed have not resolved the issues raised by empirical findings. This study provides data from judgments of four sensory continua, two visual and two tactual-kinesthetic, which show that the adaptation level for a set of stimuli serves as a category boundary whether stimuli on the continuum differ by linear or logarithmic increments. For all sensory continua studied, discrimination of stimuli belonging to different perceptual categories was more accurate than discrimination of stimuli belonging to the same perceptual category. Moreover, shifts in the adaptation level produced shifts in the location of the category boundary. The concept of Adaptation-level Based Categorization (ABC) provides a unified account of judgmental processes in categorical perception without recourse to post hoc constructs such as implicit anchors or external referents.     

Decision deadlines and uncertainty monitoring: the effect of time constraints on uncertainty and perceptual responses

The behavioral uncertainty response has grounded the study of animal metacognition and influenced the study of human psychophysics. However, the interpretation of this response is debated—especially whether it is a behavioral index of metacognition. The authors advanced this interpretation using the dissociative technique of response deadlines. Uncertainty responding, if it is higher level or metacognitive, should depend on a slower, more controlled decisional process and be more vulnerable to time constraints. Humans performed sparse–uncertain–dense or sparse–middle–dense discriminations in which, respectively, they could decline difficult trials or positively identify middle stimuli. Uncertainty responses were sharply and selectively reduced under a decision deadline, as compared to primary perceptual responses (i.e., “sparse,” “middle,” and “dense” responses). This dissociation suggests that the uncertainty response does reflect a higher-level, decisional response. It grants the uncertainty response a distinctive psychological role in its task and encourages an interpretation of this response as an elemental behavioral index of uncertainty that deserves continuing research.     

The Relationship of Nondirectiveness to Genetic Counseling: Report of a Workshop at the 2003 NSGC Annual Education Conference

Nondirectiveness has been a guiding principle for genetic counseling since the founding of the profession. However, its efficacy and appropriateness in this role have been frequently questioned. A workshop at the 2003 Annual Education Conference of the National Society of Genetic Counselors provided audience participation in a discussion of these issues. Participants presented arguments for and against nondirectiveness as a central ethos. They described complex personal transitions in adapting what they had learned about nondirectiveness during training to the realities of the workplace. There was support for flexible approaches to genetic counseling, with varying adherence to nondirectiveness, based on client and family needs and values, clinical circumstances, and desired counseling outcomes. The discussion supports the use of clinical experience, outcomes research, and the experience of other professions to move beyond nondirectiveness and more accurately identify the theoretical bases that underlie genetic counseling in the variety of circumstances in which it is currently practiced.     

Individual and social determinants of winning bids in online auctions

• Online auctions have grown in popularity since the inception of eBay in 1995. Yet despite the phenomenal growth, little is understood about the individual and collective motivations of consumers that lead to higher bids and ultimately, higher profits. This research reframes auction theory in terms of consumer behavior theory and uses observational data to assess bidder‐generated behavior in response to seller‐generated decisions. Results suggest that an increased number of visual cues (pictures) influences bids placed early in the auction and that those early bids generate activity among other bidders, subsequently resulting in higher winning bids. In addition, our findings indicate that the starting price, as determined by the seller, also impacts the final winning bid. Research and seller implications are offered, as are future directions for research in studying this still new phenomenon.

Copyright © 2006 John Wiley & Sons, Ltd.     

Two languages, one developing brain: event-related potentials to words in bilingual toddlers

Infant bilingualism offers a unique opportunity to study the relative effects of language experience and maturation on brain development, with each child serving as his or her own control. Event-related potentials (ERPs) to words were examined in 19- to 22-month-old English-Spanish bilingual toddlers. The children's dominant vs. nondominant languages elicited different patterns of neural activity in the lateral asymmetry of an early positive component (P100), and the latencies and distributions of ERP differences to known vs. unknown words from 200-400 and 400-600 ms. ERP effects also differed for 'high' and 'low' vocabulary groups based on total conceptual vocabulary scores. The results indicate that the organization of language-relevant brain activity is linked to experience with language rather than brain maturation.