Measuring saccade curvature: A curve-fitting approach

Saccade curvature is becoming a popular measure for detecting the presence of competing saccadic motor programs. Several different methods of quantifying saccade curvature have been employed. In the present study, we compared these metrics with each other and with novel measures based on curve fitting. Initial deviation metrics were only moderately associated with the more widely used metric of maximum curvature. The latter was strongly related to a recently developed area-based measure and to the novel methods based on second- and third-order polynomial fits. The curve-fitting methods showed that although most saccades curved in only one direction, there was a population of trajectories with both a maximum and a minimum (i.e., double-curved saccades). We argue that a curvature metric based on a quadratic polynomial fit deals effectively with both types of trajectories and, because it is based on all the samples of a saccade, is less susceptible to sampling noise.     

The impact of politeness and relationship on perceived quality of advice about a problem

Advice is a common but potentially problematic way to respond to someone who is distressed. Politeness theory (Brown & Levinson, 1987) suggests advice threatens a hearer's face and predicts that the speaker‐hearer relationship and the use of politeness strategies can mitigate face threat and enhance the effectiveness of advice messages. Students (N=384) read 1 of 16 hypothetical situations that varied in speaker power and closeness of the speaker‐hearer relationship. Students then read 1 of 48 advice messages representing different politeness strategies and rated the message for regard shown for face and for effectiveness. However, neither speaker‐hearer relationship nor politeness strategies was consistently associated with perceived threat to face or perceived advice effectiveness. We suggest revisions to politeness theory and additional factors that may affect judgments of face sensitivity and advice effectiveness.     

Tatsachen und Theorien der Formbildung als Weg zum Lebensproblem

Ohne Zusammenfassung Die folgende Abhandlung ist die bedeutend erweiterte Ausarbeitung eines Vortrages, welcher am 9. Januar 1929 in einer Allgemeinen Versammlung der Zoologisch-Botanischen Gesellschaft in Wien, am 15. Oktober 1929 vor der Gesellschaft für empirische Philosophie in Berlin und am 30. Oktober 1929 in der Kantgesellschaft Karlsruhe gehalten wurde. Bei der Ausarbeitung wurde vor allem Bedacht genommen, Tatsachen und Theorien, die sich bereits in des Verf.s „Kritischer Theorie der Formbildung” (Schaxels Abh. z. th. B. 27, Berlin 1928) dargestellt finden, nur kurz zu behandeln, andererseits aber das genannte Werk hier durch die Verarbeitung der dort noch nicht behandelten Ergebnisse zu erg?nzen. Auch in die Literaturangabe wurden im allgemeinen nur an jenem Orte nicht angegebene Werke aufgenommen. Auf das erw?hnte Buch, das eine umfassende, kritische Darstellung der Theorien der Formbildung zum Ziele hat, sei hier ein für allemal hingewiesen.     

Big brains are not enough: performance of three parrot species in the trap-tube paradigm

The trap-tube task has become a benchmark test for investigating physical causality in vertebrates. In this task, subjects have to retrieve food out of a horizontal tube using a tool and avoiding a trap hole in the tube. Great apes and corvids succeeded in this task. Parrots with relative brain volumes comparable to those of corvids and primates also demonstrate high cognitive abilities. We therefore tested macaws, a cockatoo, and keas on the trap-tube paradigm. All nine parrots failed to solve the task. In a simplified task, trap tubes with a slot inserted along the top were offered. The slot allowed the birds to move the reward directly with their bills. All but one individual solved this task by lifting the food over the trap. However, the parrots failed again when they were prevented from lifting the reward, although they anticipated that food will be lost when moved into the trap. We do not think that the demanding use of an external object is the main reason for the parrots’ failure. Moreover, we suppose these parrots fail to consider the trap’s position in the beginning of a trial and were not able to stop their behaviour and move the reward in the trap’s opposite direction.     

Bayesian and maximum likelihood estimation of hierarchical response time models

Hierarchical (or multilevel) statistical models have become increasingly popular in psychology in the last few years. In this article, we consider the application of multilevel modeling to the ex-Gaussian, a popular model of response times. We compare single-level and hierarchical methods for estimation of the parameters of ex-Gaussian distributions. In addition, for each approach, we compare maximum likelihood estimation with Bayesian estimation. A set of simulations and analyses of parameter recovery show that although all methods perform adequately well, hierarchical methods are better able to recover the parameters of the ex-Gaussian, by reducing variability in the recovered parameters. At each level, little overall difference was observed between the maximum likelihood and Bayesian methods.     

Visual categorization of natural stimuli by domestic dogs

One of the fundamental issues in the study of animal cognition concerns categorization. Although domestic dogs (Canis familiaris) are on the brink to become one of the model animals in animal psychology, their categorization abilities are unknown. This is probably largely due to the absence of an adequate method for testing dogs’ ability to discriminate between large sets of pictures in the absence of human cueing. Here we present a computer-automated touch-screen testing procedure, which enabled us to test visual discrimination in dogs while social cueing was ruled out. Using a simultaneous discrimination procedure, we first trained dogs (N = 4) to differentiate between a set of dog pictures (N = 40) and an equally large set of landscape pictures. All subjects learned to discriminate between the two sets and showed successful transfer to novel pictures. Interestingly, presentation of pictures providing contradictive information (novel dog pictures mounted on familiar landscape pictures) did not disrupt performance, which suggests that the dogs made use of a category-based response rule with classification being coupled to category-relevant features (of the dog) rather than to item-specific features (of the background). We conclude that dogs are able to classify photographs of natural stimuli by means of a perceptual response rule using a newly established touch-screen procedure. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Common marmosets (<Emphasis Type="Italic">Callithrix jacchus</Emphasis>) do not utilize social information in three simultaneous social foraging tasks

Social foraging is suggested to increase foraging efficiency, as individuals might benefit from public information acquired by monitoring the foraging activities of other group members. We conducted a series experiments with captive common marmosets (Callithrix jacchus) to investigate to what extent marmosets utilize social information about food location when foraging simultaneously with conspecifics. Subjects were confronted with dominant and subordinate demonstrators in three experiments which differed in the amount of information about food location available to the demonstrators. In all three experiments, the focal subjects’ performance in the social condition was not enhanced in comparison to a non-social control condition. Because we could rule out kleptoparasitism and aggressive displacements as explanations, we argue that the subjects’ tendency for scramble competition by avoiding others and dispersing over the foraging area seems to inhibit or mask the acquisition of social information about the location of rewarded patches.