Perception of translational heading from optical flow

Radial patterns of optical flow produced by observer translation could be used to perceive the direction of self-movement during locomotion, and a number of formal analyses of such patterns have recently appeared. However, there is comparatively little empirical research on the perception of heading from optical flow, and what data there are indicate surprisingly poor performance, with heading errors on the order of 5 degrees-10 degrees. We examined heading judgments during translation parallel, perpendicular, and at oblique angles to a random-dot plane, varying observer speed and dot density. Using a discrimination task, we found that heading accuracy improved by an order of magnitude, with 75%-correct thresholds of 0.66 degrees in the highest speed and density condition and 1.2 degrees generally. Performance remained high with displays of 63-10 dots, but it dropped significantly with only 2 dots; there was no consistent speed effect and no effect of angle of approach to the surface. The results are inconsistent with theories based on the local focus of outflow, local motion parallax, multiple fixations, differential motion parallax, and the local maximum of divergence. But they are consistent with Gibson's (1950) original global radial outflow hypothesis for perception of heading during translation.     

Children's predictions of consistency in people's actions

Past research suggests that young children are often reluctant to generalize about people's behavior. Three experiments involving 102 4-5-year-olds, 84 7-8-year-olds, and 107 adults explored the conditions under which inductive inferences about people are made. There was an age-based increase in propensity to predict consistency in psychological/intentional causal relations. Children often predicted change; people would behave differently in the future than they did in the past. Younger children limited predictions of consistency to non-psychological contexts. Older children showed some appreciation of stable motivations (e.g. traits, preferences). The results are consistent with the hypothesis that children's theories of mind emphasize situational influences, with personal influences appearing in middle-childhood.     

Simplified learning in complex situations: knowledge partitioning in function learning

The authors explored the phenomenon that knowledge is not always integrated and consistent but may be partitioned into independent parcels that may contain mutually contradictory information. In 4 experiments, using a function learning paradigm, a binary context variable was paired with the continuous stimulus variable of a to-be-learned function. In the first 2 experiments, when context predicted the slope of a quadratic function, generalization was context specific. Because context did not predict function values, it is suggested that people use context to gate separate learning of simpler partial functions. The 3rd experiment showed that partitioning also occurs with a decreasing linear function, whereas the 4th study showed that partitioning is absent for a linearly increasing function. The results support the notion that people simplify complex learning tasks by acquiring independent parcels of knowledge.     

Competing strategies in categorization: expediency and resistance to knowledge restructuring

The authors investigated people's ability to restructure their knowledge when additional information about a categorization task is revealed. In 2 experiments, people first learned to rely on a fairly accurate (but imperfect) predictor. At various points in training, a complex relationship between 2 other predictors was revealed in a schematic diagram that could support perfect performance. In Experiment 1, people adopted the complex strategy when it was revealed at the outset but were unable to restructure their knowledge after the expedient predictor had been learned. In Experiment 2, expedient knowledge persisted even with an adaptive display. The persistence of expedient knowledge is explained by associative blocking of potential alternative cues. A 3rd experiment analyzed the strategies people use with and without the diagram. The study confirmed that the diagram, when presented at the outset, significantly alters people's approach to the task.     

Remote delivery of cognitive science laboratories: A solution for small disciplines in large countries

Numerically small disciplines can be jeopardized by geographic difficulties, if student populations at universities are small and distances between them large. This problem could be addressed, if teaching resources could be shared among several universities and students in several locations could be taught simultaneously. We present the results of a trial in simultaneous Internet and videoconferencing delivery of an introductory cognitive science laboratory. The trial relied on off-the-shelf software and hardware. Students found the delivery nearly as effective as a locally run laboratory, despite a noticeable difference in the level of interactivity between the remote and other, local laboratory classes. We discuss possible further improvements in teaching efficiency and efficacy.     

The inheritance of desired characteristics: Children's view of the role of intention in parent-offspring resemblance.

Two studies examined children's beliefs about maternal intention as a mechanism for trait inheritance. In Study 1, 42 preschool-aged (4 to 5 years old) children and 81 adults were shown pictures of adult women (mothers) and were asked to identify their daughters. In the critical condition participants were asked to choose between a girl who shared an attribute with the mother and a girl who had the attribute desired by the mother. Trait types included physically heritable traits, nonheritable traits, and beliefs. Results from this study suggest that preschoolers do believe that maternal intention plays a role in the inheritance of physical traits. Study 2 was designed to determine whether preschoolers recognize limits on both the efficacy and the timing of maternal intention. Results suggest that children see some properties as outside of maternal control. Further, they do seem to see maternal intentions as operating prior to birth. One finding of these studies is that preschoolers may not have strong intuitions that offspring will resemble their parents. In addition, children seem to have different intuitions about the mechanisms of inheritance than do adults.     

Generalizing norms and preferences within social categories and individuals

Under what conditions will people generalize and remember observed social information? Preschool- (n = 44) and young school-age (n = 46) children and adults (n = 40) heard short vignettes describing characters' actions and motives on a single occasion. Characters were introduced using either proper names or category labels. Test questions asked for prediction and memory of motives for the same (individual) or a different (category member) person in a future event. Critical items contrasted behaviors motivated by psychological states with those motivated by normative obligations. The hypothesis was that norms would generalize across members of social categories. In contrast, psychological states would be generalized to the same individual across time. Results supported both these hypotheses and revealed some developmental differences. Preschool-age children seemed most attentive to normative properties of social categories. Young school-age children were most attentive to psychological properties of individuals. Such differences may reflect a shift from early focus on within-category similarities to a later focus on within-category differences.     

Postural asymmetries in response to holding evenly and unevenly distributed loads during self-selected stance

The authors examined postural asymmetries during quiet stance and while holding evenly or unevenly distributed loads. Right-hand dominant subjects preferentially loaded their right lower limb when holding no load or a load evenly distributed in both hands, but no differences in center of pressure (CoP) were observed between the left and right limbs. However, longer CoP displacement was observed under the preferentially loaded limb, which may reflect a functional asymmetry that allows quick movement of one limb in response to a potential perturbation. When a load was held only in the nondominant hand, sample entropy decreased in the left (loaded) limb but increased in the right (unloaded) limb, suggesting the unloaded foot compensated for a loss of control flexibility in the loaded foot.     

Young Children Choose to Inform Previously Knowledgeable Others

Children recognize that people who know more are better informants than those who know less. How does an individual’s prior knowledge affect children’s decisions about whom to inform? In 3 experiments, 3- to 6-year-old children were invited to share a novel piece of information with 1 of 2 potential recipients who differed in their recent history of knowledge. Children tended to inform the previously knowledgeable person rather than the previously ignorant person. This same effect was observed in a 4th experiment when the knowledgeable person stated that she already knew the information the participant had to share. In no case was the opposite pattern observed: Children never chose to inform the person who had known less. These results seem to conflict with equity considerations and may reflect a preference to affiliate with competent social partners.     

Iterated learning: Intergenerational knowledge transmission reveals inductive biases

Cultural transmission of information plays a central role in shaping human knowledge. Some of the most complex knowledge that people acquire, such as languages or cultural norms, can only be learned from other people, who themselves learned from previous generations. The prevalence of this process of “iterated learning” as a mode of cultural transmission raises the question of how it affects the information being transmitted. Analyses of iterated learning utilizing the assumption that the learners are Bayesian agents predict that this process should converge to an equilibrium that reflects the inductive biases of the learners. An experiment in iterated function learning with human participants confirmed this prediction, providing insight into the consequences of intergenerational knowledge transmission and a method for discovering the inductive biases that guide human inferences.