Rats remember not wisely but too well

Rats were trained in a three-alternative spatial delayed matching-to-sample task in a starburst maze. Samples consisted of rewarded forced choices of one arm, and retention was indicated by rats’ returning to that arm after a 90-sec delay. If a rat made an error on its first choice, it was returned to the start compartment and allowed a second choice. Unlike in previous experiments with this task, all three arms were available during the animals’ second choices. The rats tended to perseverate in their second choices by returning to the arm that they had erroneously visited on their first choice. In Experiment 1, the accuracy of second choices following first-choice errors was below chance during the first block of sessions, when a 90-sec delay intervened between the first choice and the second choice, and at chance during the second block of sessions, when a short (5–6 see) delay intervened between first and second choices. In Experiment 2, long-delay and short-delay sessions were randomly presented to naive subjects. Similar results were obtained. In both experiments, the tendency to repeat the erroneous first choice was greater when long delays separated the two choices than when short delays were used. The results suggest that rats make their first-choice errors because they erroneously encode or remember the location of the sample and that they base their second choices on the same erroneous-memory. The increase in perseveration at long delays implies some kind of rehearsal-like mechanism that slows forgetting of the memory controlling the first choice.     

Application of Think Aloud Protocols for Examining and Confirming Sources of Differential Item Functioning Identified by Expert Reviews

This paper demonstrates and discusses the use of think aloud protocols (TAPs) as an approach for examining and confirming sources of differential item functioning (DIF). The TAPs are used to investigate to what extent surface characteristics of the items that are identified by expert reviews as sources of DIF are supported by empirical evidence from examinee thinking processes in the English and French versions of a Canadian national assessment. In this research, the TAPs confirmed sources of DIF identified by expert reviews for 10 out of 20 DIF items. The moderate agreement between TAPs and expert reviews indicates that evidence from expert reviews cannot be considered sufficient in deciding whether DIF items are biased and such judgments need to include evidence from examinee thinking processes.     

Validation of Weinbach's and Hanavan's Models for Computation of Physical Properties of the Forearm

Abstract

The purpose of the present study was to validate the Weinbach and the Hanavan models for the determinations of the forearm volume and center of mass. The study was conducted using 20 forearms from six male and four female cadavers. Results from the present investigation indicate that Weinbach's model is more accurate than Hanavan's model in estimating forearm volume and center of mass. The relative location of the center of mass and the center of volume was also investigated with the Weinbach model and these centers were found to coincide. The Hanavan model should be used only in the cases where the shape of the forearm closely resembles that of a truncated cone.     

Development and Validation of a Method for Determining Tridimensional Angular Displacements with Special Applications to Ice Hockey Motions

Abstract

Tridimensional angular displacements of the skates were determined with a single cinecamera used in conjunction with two orthogonal rods attached to the rear part of the skater's boots. The method was based on the commutative law with the imposed restrictions that two of the angles were small in relation to the other one, and that a sequence of angular displacements was defined. This approach required the sole determinations of the planar coordinates of the three points delimiting the orthogonal rods. An experimental setup was designed to validate the method: the criterion angles were approximated with less than 2 degrees of error. Subsequently, the method was applied to a practical situation: the two-legged stop in ice hockey. The combination of this tridimensional method with instrumented strain gauge skates for the measurement of forces provides a new and powerful tool for performing kinetic analyses in tridimensional skating activities.     

Glutaraldehyde enhanced dielectrophoretic yeast cell separation

We introduce a method for improved dielectrophoretic (DEP) discrimination and separation of viable and nonviable yeast cells. Due to the higher cell wall permeability of nonviable yeast cells compared with their viable counterpart, the cross-linking agent glutaraldehyde (GLT) is shown to selectively cross-link nonviable cells to a much greater extent than viable yeast. The DEP crossover frequency (cof) of both viable and nonviable yeast cells was measured over a large range of buffer conductivities (22 μS∕cm–400 μS∕cm) in order to study this effect. The results indicate that due to selective nonviable cell cross-linking, GLT modifies the DEP cof of nonviable cells, while viable cell cof remains relatively unaffected. To investigate this in more detail, a dual-shelled oblate spheroid model was evoked and fitted to the cof data to study cell electrical properties. GLT treatment is shown to minimize ion leakage out of the nonviable yeast cells by minimizing changes in cytoplasm conductivity over a large range of ionic concentrations. This effect is only observable in nonviable cells where GLT treatment serves to stabilize the cell cytoplasm conductivity over a large range of buffer conductivity and allow for much greater differences between viable and nonviable cell cofs. As such, by taking advantage of differences in cell wall permeability GLT magnifies the effect DEP has on the field induced separation of viable and nonviable yeasts.     

The effects of skin and core tissue cooling on oxygenation of the vastus lateralis muscle during walking and running

Skin and core tissue cooling modulates skeletal muscle oxygenation at rest. Whether tissue cooling also influences the skeletal muscle deoxygenation response during exercise is unclear. We evaluated the effects of skin and core tissue cooling on skeletal muscle blood volume and deoxygenation during sustained walking and running. Eleven male participants walked or ran six times on a treadmill for 60 min in ambient temperatures of 22°C (Neutral), 0°C for skin cooling (Cold 1), and at 0°C following a core and skin cooling protocol (Cold 2). Difference between oxy/deoxygenated haemoglobin ([diffHb]: deoxygenation index) and total haemoglobin content ([tHb]: total blood volume) in the vastus lateralis (VL) muscle was measured continuously. During walking, lower [tHb] was observed at 1 min in Cold 1 and Cold 2 vs. Neutral (P?0.05). Lower [diffHb] was seen at 1 and 10 min in Cold 2 vs. Neutral by 13.5 ± 1.2 µM and 15.3 ± 1.4 µM and Cold 1 by 10.4 ± 3.1 µM and 11.1 ± 4.1 µM, respectively (P?0.05). During running, [tHb] was lower in Cold 2 vs. Neutral at 10 min only (P = 0.004). [diffHb] was lower at 1 min in Cold 2 by 11.3 ± 3.1 µM compared to Neutral and by 13.5 ± 2.8 µM compared to Cold 1 (P?0.001). Core tissue cooling, prior to exercise, induced greater deoxygenation of the VL muscle during the early stages of exercise, irrespective of changes in blood volume. Skin cooling alone, however, did not influence deoxygenation of the VL during exercise.     

Participatory Scaling Through Augmented Reality Learning Through Local Games

The proliferation of broadband mobile devices, which many students bring to school with them as mobile phones, makes the widespread adoption of AR pedagogies a possibility, but pedagogical, distribution, and training models are needed to make this innovation an integrated part of education, This paper employs Social Construction of Technology (SCOT) to argue for a participatory model of scaling by key stakeholders groups (students, teachers, researchers, administrators), and demonstrates through various cases how ARIS (arisgames.org) — a free, open-source tool for educators to create and disseminate mobile AR learning experiences — may be such a model.     

Search behavior of dogs (Canis familiaris) in invisible displacement problems

Gagnon and Doré (1992) showed that domestic dogs are able to solve a Piagetian object permanence task called the invisible displacement problem. A toy is hidden in a container which is moved behind a screen where the toy is removed and left. Dogs make more errors in these problems than they do in visible displacement tests, in which the object is hidden directly behind the target screen. In Experiment 1, we examined components of the standard procedure of invisible displacements that may make encoding or retention of the hiding location more difficult than it is in visible displacements. In Experiment 2, we compared dogs’ performances in visible and invisible displacement problems when delays of 0, 10, and 20 sec were introduced between the object’s final disappearance and the subject’s release. The results revealed that dogs’ poorer performance in invisible displacement tests is related to the complex sequence of events that have to be encoded or remembered as well as to a difficulty in representing the position change that is signaled, but not directly perceived.     

GENDER DIFFERENCES IN WRITTEN EXPRESSION CURRICULUM‐BASED MEASUREMENT IN THIRD‐ THROUGH EIGHTH‐GRADE STUDENTS

Many studies have found gender differences in certain areas of academic achievement, such as reading and math. Fewer studies have examined gender disparities in writing skills. The current study explored gender differences in written expression performance. Participants were 1,240 male and female students in third through eighth grade, representing five schools in a rural southeastern school district. Each student was administered an AIMSweb curriculum‐based measurement writing probe during the district's regularly scheduled fall, winter, and spring benchmarks. All measures were scored for total words written and correct writing sequences. Two‐way repeated measures analyses of variance were used to determine whether differences existed in the sample. A significant female advantage was found on both scoring indices at each grade level. These findings have strong instructional and theoretical implications for practicing school psychologists and other educators.     

Videogames and spatial skills: An exploratory study

Fifty-eight undergraduate and graduate students participated in an exploratory study which examined the relationship between videogames, spatial cognitive skills, and eye-hand coordination. Scores on two videogames were compared with subjects’ scores on three standardized spatial skills tests and on one test of eye-hand coordination. The subjects were randomly assigned to either the experimental group (which was provided with five hours of videogame practice) or the control group (which was provided with no videogame practice). The scores on the two videogames were found to be correlated with different spatial test scores. Significant sex and age differences were also found on several of the measures. The males scored higher than the females on spatial orientation, visualization, and the baseline measures on one of the videogames, while the females scored higher than the males on the test of eye-hand coordination. The age of the subjects was found to be negatively correlated with scores on the videogames and spatial test scores. I would like to acknowledge the significant contributions of my advisers Ronald Slaby and Barbara Flagg of Harvard Graduate School of Education, America’s Game of Somerville, MA, for equipment donation, and John Kao of the Harvard Business School for donating the use of computer facilities.