Akinetopsia,achromatopsia and blindsight: Recent studies on perception without awareness

The neural substrate of early visual processing in the macaque is used as a framework to discuss recent progress towards a precise anatomical localization and understanding of the functional implications of the syndromes of blindsight, achromatopsia and akinetopsia in humans. This review is mainly concerned with how these syndromes support the principles of organization of the visual system into parallel pathways and the functional hierarchy of visual mechanisms.     

Motion aftereffects with rotating ellipses

Summary The perceptual outcome and the motion-aftereffect duration generated by the rotation on the frontal plane of an ellipse with a bar depend on whether the bar is placed along the major or the minor axis. When the bar is placed along the minor axis, a stereokinetic transformation occurs, and the pattern looks like a tilting ring with a perpendicular bar moving rigidly with it. Placing the bar along the major axis prevents the stereokinetic transformation: subjects report deformations and relative motion of the bar with respect to the ellipse. We found that motion aftereffects last longer when the bar is placed along the minor rather than along the major axis. A series of experiments was carried out to investigate whether differences in aftereffect duration are related to the stereokinetic transformation. Results seem to suggest that they are not.The authors' names are in alphabetical order.     

The Perfect Mix: Regulatory Complementarity and the Speed-Accuracy Balance in Group Performance

ABSTRACT— In this research, we varied the composition of 4-member groups. One third of the groups consisted exclusively of "locomotors," individuals predominantly oriented toward action. Another third of the groups consisted exclusively of "assessors," individuals predominantly oriented toward evaluation. The final third of the groups consisted of a mix of locomotors and assessors. We found that the groups containing only locomotors were faster than the groups containing only assessors, and the groups containing only assessors were more accurate than the groups containing only locomotors. The groups containing a mix of assessors and locomotors were as fast as the groups containing only locomotors and as accurate as the groups containing only assessors. These results echo findings at the individual level of analysis, and suggest that the testing and action components of operating systems independently contribute to performance both intra- and interpersonally.     

Acquisition of a visual discrimination and reversal learning task by Labrador retrievers

Optimal cognitive ability is likely important for military working dogs (MWD) trained to detect explosives. An assessment of a dog’s ability to rapidly learn discriminations might be useful in the MWD selection process. In this study, visual discrimination and reversal tasks were used to assess cognitive performance in Labrador retrievers selected for an explosives detection program using a modified version of the Toronto General Testing Apparatus (TGTA), a system developed for assessing performance in a battery of neuropsychological tests in canines. The results of the current study revealed that, as previously found with beagles tested using the TGTA, Labrador retrievers (N = 16) readily acquired both tasks and learned the discrimination task significantly faster than the reversal task. The present study confirmed that the modified TGTA system is suitable for cognitive evaluations in Labrador retriever MWDs and can be used to further explore effects of sex, phenotype, age, and other factors in relation to canine cognition and learning, and may provide an additional screening tool for MWD selection.     

Hemispheric differences in the recognition of partly occluded objects by newly hatched domestic chicks (<Emphasis Type="Italic">Gallus gallus</Emphasis>)

Domestic chicks are capable of perceiving as a whole objects partly concealed by occluders (amodal completion). In previous studies chicks were imprinted on a certain configuration and at test they were required to choose between two alternative versions of it. Using the same paradigm we now investigated the presence of hemispheric differences in amodal completion by testing newborn chicks with one eye temporarily patched. Separate groups of newly hatched chicks were imprinted binocularly: (1) on a square partly occluded by a superimposed bar, (2) on a whole or (3) on an amputated version of the square. At test, in monocular conditions, each chick was presented with a free choice between a complete and an amputated square. In the crucial condition 1, chicks tested with only their left eye in use chose the complete square (like binocular chicks would do); right-eyed chicks, in contrast, tended to choose the amputated square. Similar results were obtained in another group of chicks imprinted binocularly onto a cross (either occluded or amputated in its central part) and required to choose between a complete or an amputated cross. Left-eyed and binocular chicks chose the complete cross, whereas right-eyed chicks did not choose the amputated cross significantly more often. These findings suggest that neural structures fed by the left eye (mainly located in the right hemisphere) are, in the chick, more inclined to a global analysis of visual scenes, whereas those fed by the right eye seem to be more inclined to a featural analysis of visual scenes.     

Clinical Trial Application in Europe: What Will Change with the New Regulation?

The European framework surrounding clinical trials on medicinal products for human use is going to change as demonstrated by the large debate at European institutional level. One of the major challenges is to overcome the lack of harmonisation of clinical trial procedures among countries. This aspect is gaining more and more importance, considering the increasing number of multicentre and multinational studies. In this work, the actual European rules governing the Clinical Trial Application have been analysed throughout the different steps including the registration of the trial in the European database; the preparation of documents to be submitted and their contents; the preparation of documents related to the information and consent process; the submission to competent bodies. Specific issues related to paediatric research and trials involving non EU/EEA countries have been addressed as well. Results reveal that the European legislation offers a well defined set of European rules covering different aspects of a Clinical Trial Application. However, these are not suitable to meet the challenges from multicentre and multinational clinical studies. A stronger set of rules, such as is available in a composite European Regulation has been adopted and is expected to harmonise practices and enable sponsors to carry out well conducted trials. But will the new regulation overcome the existing criticisms of Directive 2001/20/EC?     

Discrimination of small numerosities in young chicks

Chicks were trained to discriminate small sets of identical elements. They were then tested for choices (unrewarded) between sets of similar numerosities, when continuous physical variables such as spatial distribution, contour length, and overall surface were equalized. In all conditions chicks discriminated one versus two and two versus three stimulus sets. Similar results were obtained when elements were presented under conditions of partial occlusion. In contrast, with sets of four versus five, four versus six, and three versus four elements chicks seemed unable to discriminate on the basis of number, although nonnumerical discrimination based on perceptual cues was observed. This adds to increasing evidence for discrimination of small numerosities of up to three elements in human infants and nonhuman animals.     

Construct validity and generalizability of the Carver–White behavioural inhibition system/behavioural activation system scales

The factorial structure and invariance of the BIS/BAS scales of Carver and White were assessed across three samples from the USA, UK, and Italy. Previous validation studies of the BIS/BAS scales relied on individual samples drawn from English‐speaking populations only and failed to formally assess generalizability. The current study shows that the four‐factor structure proposed by Carver and White—i.e. one BIS and three BAS facets—achieved satisfactory psychometric properties in all three samples and that measurement invariance was obtained across countries. Latent mean differences due to gender and country were also investigated. Theoretical issues concerning the validity of the BIS/BAS scales are addressed. Copyright © 2001 John Wiley & Sons, Ltd.     

Location and shape in inhibition of return

Inhibition of return (IOR) is characterized by a delay in responding to a target preceded by an irrelevant stimulus (cue) at the same location, or, in other words, by a response delay when the same location is stimulated twice. It is not clear, however, if the same phenomenon is present when there is a repetition of a simple nonspatial attribute of the stimulus. The present study examines the repetition of shape. Six experiments were conducted. In Experiments 1, 2, 3, and 6 the stimuli were geometrical shapes, whereas in Experiments 4 and 5 letters were used. In Experiment 1 all the stimuli were presented at fixation, whereas in Experiments 2 to 6 they were presented in the periphery. In Experiments 2 and 3, location and shape of the cue and the target were independently manipulated in order to test independently inhibitory effects (IOR?) attributable to location repetition and shape repetition. Results showed an inhibitory effect for location and a much smaller inhibitory effect for shape. The latter was restricted to the cued location. Experiments 4 and 5 tested the possibility that inhibition caused by shape repetition is due to repetition blindness. Experiment 6 contrasted the presence or absence of a central neutral attractor in the delay interval between presentation of the cue and the target. Taken together the results seem to favor IOR as the basis for the inhibition caused by shape repetition.