A Contextual Approach to Scientific Understanding

Achieving understanding of nature is one of the aims of science. In this paper we offer an analysis of the nature of scientific understanding that accords with actual scientific practice and accommodates the historical diversity of conceptions of understanding. Its core idea is a general criterion for the intelligibility of scientific theories that is essentially contextual: which theories conform to this criterion depends on contextual factors, and can change in the course of time. Our analysis provides a general account of how understanding is provided by scientific explanations of diverse types. In this way, it reconciles conflicting views of explanatory understanding, such as the causal-mechanical and the unificationist conceptions.     

Reversibility of the other-race effect in face recognition during childhood

Early experience with faces of a given racial type facilitates visual recognition for this type of face relative to others. To assess whether this so-called other-race effect can be reversed by subsequent experience with new types of faces, we tested adults of Korean origin who were adopted by European Caucasian families when they were between the ages of 3 to 9. The adoptees performed a face recognition task with photographs of Caucasian and Asian faces. They performed exactly like a control group of French participants, identifying the Caucasian faces better than the Asiatic ones. In contrast, a control group of Koreans showed the reverse pattern. This result indicates that the face recognition system remains plastic enough during childhood to reverse the other-race effect.     

Word frequency of irrelevant speech distractors affects serial recall

In this study, participants memorized frequent or rare target words in silence or while ignoring frequent or rare distractor words. Distractor words impaired recall performance, but low-frequency distractor words caused more impairment than did high-frequency distractor words. We demonstrate how to solve the identifiability problem for Schweickert's (1993) multinomial processing tree model of immediate recall, and then use this model to show that irrelevant speech affected both the probability with which intact target word representations were available for serial recall and the probability of successful reconstruction of item identities based on degraded short-term memory traces. However, the type of irrelevant speech--low-versus high-frequency words--selectively affected the probability of intact target word representations. These results are consistent with an explanation of the irrelevant speech effect within the framework proposed by Cowan (1995), and they pose problems for other explanations of the irrelevant speech effect. The analyses also confirm the validity of Schweickert's process model.     

On the speed of intuition: Intuitive judgments of semantic coherence under different response deadlines

Intuition is the ability to judge stimulus properties on the basis of information that is activated in memory but not consciously retrieved. We investigated one central feature of intuitive judgments--namely, their speed. Participants judged whether or not three clue words were coherent in the sense that they were weakly associated with a common fourth concept. To restrict the time available for conscious deliberation of possible solution words, participants had to synchronize their judgments with a response signal appearing at different lags after the clue words. In two experiments, participants discriminated coherent and incoherent triads reliably better than chance, even when they did not consciously retrieve the solution word and the lag between clue words and response signal was as short as 1.5 sec. Results indicate that intuitive judgments can indeed be made very fast and without extended conscious deliberation. Possible mechanisms underlying intuitive judgments are discussed.     

A dynamic developmental theory of attention-deficit/hyperactivity disorder (ADHD) predominantly hyperactive/impulsive and combined subtypes

Attention-deficit/hyperactivity disorder (ADHD) is currently defined as a cognitive/behavioral developmental disorder where all clinical criteria are behavioral. Inattentiveness, overactivity, and impulsiveness are presently regarded as the main clinical symptoms. The dynamic developmental behavioral theory is based on the hypothesis that altered dopaminergic function plays a pivotal role by failing to modulate nondopaminergic (primarily glutamate and GABA) signal transmission appropriately. A hypofunctioning mesolimbic dopamine branch produces altered reinforcement of behavior and deficient extinction of previously reinforced behavior. This gives rise to delay aversion, development of hyperactivity in novel situations, impulsiveness, deficient sustained attention, increased behavioral variability, and failure to "inhibit" responses ("disinhibition"). A hypofunctioning mesocortical dopamine branch will cause attention response deficiencies (deficient orienting responses, impaired saccadic eye movements, and poorer attention responses toward a target) and poor behavioral planning (poor executive functions). A hypofunctioning nigrostriatal dopamine branch will cause impaired modulation of motor functions and deficient nondeclarative habit learning and memory. These impairments will give rise to apparent developmental delay, clumsiness, neurological "soft signs," and a "failure to inhibit" responses when quick reactions are required. Hypofunctioning dopamine branches represent the main individual predispositions in the present theory. The theory predicts that behavior and symptoms in ADHD result from the interplay between individual predispositions and the surroundings. The exact ADHD symptoms at a particular time in life will vary and be influenced by factors having positive or negative effects on symptom development. Altered or deficient learning and motor functions will produce special needs for optimal parenting and societal styles. Medication will to some degree normalize the underlying dopamine dysfunction and reduce the special needs of these children. The theory describes how individual predispositions interact with these conditions to produce behavioral, emotional, and cognitive effects that can turn into relatively stable behavioral patterns.     

Summoning White Bears or Letting Them Free: The Influence of the Content of Control Instructions on Target Thought Frequency

In the clinical literature, thought suppression is considered to play a role in the development of intrusion-related psychiatric syndromes, such as obsessive-compulsive disorder, acute or posttraumatic stress disorder, phobias, and addiction. This assumption goes back to a study by D. M. Wegner, D. J. Schneider, S. R. Carter, and T. L. White (1987) in which participants were asked to suppress thoughts of a white bear, an assignment that proved to be nearly impossible to complete. The present two studies sought to explore the influence of the content of control instructions on intrusion frequency in thought suppression experiments. Notably, during nonsuppression (i.e., control) periods, participants can either be instructed to think about white bears (i.e., expression instruction), or to think of anything including white bears (i.e., liberal instruction). Results indicated that expression instructions resulted in an increased number of target thoughts, while liberal instructions did not. Implications for the interpretation of thought suppression findings are discussed.     

A dynamic investigation of cognitive dedifferentiation with control for retest: evidence from the Swiss Interdisciplinary Longitudinal Study on the Oldest Old

Empirical examinations of the hypothesis of dedifferentiation of cognitive abilities in old and very old age (a) do not account for possible retest effects, which consequently may yield biased estimates of age effects, and (b) focus on time-independent relations (e.g., number of latent constructs, correlations between latent or measured variables). The authors applied a structural equation model with statistical control for retest effects to investigate the dynamic relations between a marker of perceptual speed (cross out) and a marker of verbal fluency (category-fruits). Longitudinal data are from 5 waves of the Swiss Interdisciplinary Longitudinal Study on the Oldest Old (N = 377, baseline age range = 79.5- 84.5 years). The authors found that, independently of retest effects, performance on the cross-out task affected changes in performance on the category task while the opposite did not hold true. This analytical technique could be applied to various markers of broad fluid-mechanic and broad crystallized-pragmatic components of cognition.     

Assessment of the hypochondriasis domain: the multidimensional inventory of hypochondriacal traits (MIHT)

Although hypochondriasis is associated with the costly use of unnecessary medical resources, this mental health problem remains largely neglected. A lack of clear conceptual models and valid measures has impeded accurate assessment and hindered progress. The Multidimensional Inventory of Hypochondriacal Traits (MIHT) addresses these deficiencies with scales that correspond to a 4-factor model. The MIHT was built with construct validity as a guiding principle and began with an item pool that broadly assessed dimensions identified in the literature. The items were administered to large samples; factor analyses of the responses led to item pool revisions and scale refinements. Multiple studies validated the final MIHT scales and 4-factor model; these findings suggest that the MIHT will contribute to theory and research.     

Sequential task predictability in task switching

Many studies of task switching have found that a prolonged preparation time reduces switch costs. An alternative manipulation of task preparation is based on sequential task predictability, rather than preparation time. In Experiments 1 and 2 of the present study, participants performed explicitly instructed task sequences (i.e., AABB) and were then transferred to a random sequence. The observed benefit of predictability-based task preparation was not switch specific. In Experiment 3, the participants changed from random to predictable tasks. The observed predictability benefit again was not switch specific. The data thus suggest that task switching does not necessarily require a switch-specific reconfiguration process. Rather, task-specific control processes may be needed in both task switches and repetitions.     

The role of similarity in deductive categorical inference

The category inclusion rule specifies that categories inherit the properties of their superordinates. For example, given thatall metals are pentavalent, it can be concluded thatall iron is pentavalent. Sloman (1998) showed that people do not fully endorse conclusions that follow from the category inclusion rule. He claims that people rely on the similarity between the premise and the conclusion categories (metals andiron), rather than applying the category inclusion rule. By allowing reasoners to rate their certainty for category relations (e.g.,iron is metal), as well as for conclusions, the present study shows that similarity has only an indirect effect on the certainty of conclusions: Reasoners are more certain that similar categories have a category inclusion relation, and this in turn affects the certainty of conclusions based on this relation.