Explanatory schema and the process of model building

Synthese - In this paper, we argue that rather than exclusively focusing on trying to determine if an idealized model fits a particular account of scientific explanation, philosophers of science...     

Floral guidance of learning a preference for symmetry by bumblebees

This study examines the mechanism underlying one way in which bumblebees are known to develop a preference for symmetric patterns: through prior non-differential reinforcement on simple patterns (black discs and white discs). In three experiments, bees were given a choice among symmetric and asymmetric black-and-white non-rewarding patterns presented at the ends of corridors in a radial maze. Experimental groups had prior rewarded non-discrimination training on white patterns and black patterns, while control groups had no pre-test experience outside the colony. No preference for symmetry was obtained for any of the control groups. Prior training with circular patterns highlighting a horizontal axis of symmetry led to a specific subsequent preference for horizontal over vertical symmetry, while training with a vertical axis abolished this effect. Circles highlighting both axes created a general avoidance of asymmetry in favour of symmetric patterns with vertical, horizontal or both axes of symmetry. Training with plain circles, but not with deformed circles, led to a preference for symmetry: there was no evidence that the preference emerged just by virtue of having attention drawn away from irrelevant pattern differences. Our results point to a preference for symmetry developing gradually through first learning to extract an axis of symmetry from simple patterns and subsequently recognizing that axis in new patterns. They highlight the importance of continued learning through non-differential reinforcement by skilled foragers. Floral guides can function not only to guide pollinators to the source of reward but also to highlight an axis of symmetry for use in subsequent floral encounters.     

Faces elicit different scanning patterns depending on task demands

Eye movements were recorded while participants discriminated upright and inverted faces that differed with respect to either configural or featural information. Two hypotheses were examined: (1) whether featural and configural information processing elicit different scanning patterns; (2) whether fixations on a specific region of the face dominate scanning patterns. Results from two experiments were compared to examine whether participants’ prior knowledge of the kind of information that would be relevant for the task (i.e., configural vs featural) influences eye movements. In Experiment 1, featural and configural discrimination trials were presented in random order such that participants were unaware of the information that would be relevant on any given trial. In Experiment 2, featural and configural discrimination trials were blocked and participants were informed of the nature of the discriminations. The results of both experiments suggest that faces elicit different scanning patterns depending on task demands. When participants were unaware of the nature of the information relevant for the task at hand, face processing was dominated by attention to the eyes. When participants were aware that relational information was relevant, scanning was dominated by fixations to the center of the face. We conclude that faces elicit scanning strategies that are driven by task demands.     

Physical Activity,Suicide Risk Factors,and Suicidal Ideation in a Veteran Sample

The association between current level of suicidal ideation and physical activity was tested in a broad sample of veterans seeking care from the Veterans Health Administration. It was hypothesized that the two variables would be significantly inversely related. It was further hypothesized that the relationship would be mediated by depressive symptoms, disturbed sleep, and a measure of heart rate variability based on existing research regarding physical activity and sleep. Due to the first hypothesis not being supported, the second could not be tested. Post hoc correlation analyses did find associations between physical activity and depressive symptoms, in expected directions, and are discussed. Possible explanations for the negative findings along with recommendations for future research to continue exploring links between suicide risk and physical activity are presented. We conclude by suggesting that physical activity may have promise as a risk reduction intervention and that prospective data are more likely to yield significant results than the cross‐sectional methodology employed in the current study.     

Feature distribution and background knowledge in category learning

Three experiments examined the interactions of category structure and prior knowledge in category learning.Experiment 1 examined the distribution of atypical or 'crossover' features in category learning. In real categories, crossover features may be unevenly distributed found primarily in very unusual examples of a category (like whales or ostriches). In contrast, in many psychology experiments, each item has exactly one crossover feature. Even versus uneven distribution of crossover features did not affect category learning when the features were neutral. However, when the features were connected by prior knowledge, it was much harder for subjects to learn the structure with the uneven distribution of crossover features. Experiments 2 and 3 found similar results with a slightly less uneven condition. We conclude that learning is a function of the interaction of category structure and prior knowledge rather than either one alone. Furthermore, knowledge benefits learning even when the category contains contradictions of the knowledge, so long as the contradictions are not very salient.     

The acquisition of category structure in unsupervised learning

Four experiments examined the extent to which prior knowledge influences the acquisition of category structure in unsupervised learning conditions. Prior knowledge is general knowledge about a broad domain that explains why an object has the features it does. Category structure refers to the statistical regularities of features within and across categories. Subjects viewed items and then divided them up into the categories that seemed most natural. Each item had one feature that was related to prior knowledge and five features that were not. The results showed that even this small amount of prior knowledge helped subjects to discover the category structure. In addition, prior knowledge enhanced the learning of many of the category's features, and not just the features that were directly relevant to the knowledge. The results suggest that prior knowledge may help to integrate the features of a category, thereby improving the acquisition of category structure.     

The effects of spatial frequency overlap on face recognition

The effects of spatial frequency overlap between pairs of low-pass versus high-pass images on face recognition and matching were examined in 6 experiments. Overlap was defined as the range of spatial frequencies shared by a pair of filtered images. This factor was manipulated by processing image pairs with high-pass/low-pass filter pairs whose 50% cutoff points varied in their separation from one another. The effects of the center frequency of filter pairs were also investigated. In general, performance improved with greater overlap and higher center frequency. In control conditions, the image pairs were processed with identical filters and thus had complete overlap. Even severely filtered low-pass or high-pass images in these conditions produced superior performance. These results suggest that face recognition is more strongly affected by spatial frequency overlap than by the frequency content of the images.     

Newborn Screening for Cystic Fibrosis: Parents’ Preferences Regarding Counseling At the Time of Infants’ Sweat Test

Newborn screening (NBS) protocols for cystic fibrosis (CF) are the first regional population-based programs to incorporate DNA analysis into their procedures. Research about these programs can inform policy and practice regarding how best to counsel families with abnormal NBS results. The grounded theory method guided interviews with 33 families whose infants had abnormal CF NBS results. A dimensional analysis of these interviews provided a theoretical framework describing parents’ preferences regarding counseling during their infant's sweat test appointment. This framework describes the contexts and characteristics of the two main dimensions of parents’ preferences: factual information and emotional support. Factual information included learning about the probability of a CF diagnosis, CF disease facts, sweat test procedure, and CF genetics. Social support consisted of offering parents a choice about the timing and amount of CF information, showing empathy for their distress, instilling hope, personalizing counseling, and providing hospitality. This framework also explains the consequences of counseling that matched versus mismatched parental preferences in these domains. Counseling that matched parents preferences reduced parents’ distress while mismatched counseling tended to increase parents’ worry about their infant.     

Dopamine D2 receptors mediate reversal learning in male C57BL/6J mice

Dopamine is critical for directing goal-oriented behavior. We investigated dopamine D₂ receptor involvement in reversal learning and reinforcement efficacy in mice lacking functional dopamine D₂ receptors and their heterozygous and wild-type littermates. Mice discriminated between two odors to receive a food reinforcer: One odor signaled a reinforcer (S⁺); the other odor signaled no reinforcer (S⁻). After mice learned the S⁺/S⁻ relationship, we inverted the reinforcement contingencies. The necessary number of trials to relearn the new reinforcement contingencies served as our index of reversal learning. Mice lacking functional dopamine D₂ receptors repeatedly failed to inhibit previously reinforced responses during reversal trials. In a separate experiment, mice responded for reinforcers on a progressive ratio schedule of reinforcement. Mice lacking functional dopamine D₂ receptors earned significantly fewer reinforcers than did heterozygous mice. Our results suggest that dopamine D₂ receptors regulate reversal learning and influence the reinforcing efficacy of natural rewards.