Response-based strengthening in task shifting: evidence from shift effects produced by errors

The hypothesis is introduced that 1 source of shift costs is the strengthening of task-related associations occurring whenever an overt response is produced. The authors tested this account by examining shift effects following errors and error compensation processes. The authors predicted that following a specific type of error, called task confusion, shift benefits instead of shift costs should result. A series of 3 experiments confirmed this prediction showing that task confusions produce shift benefits in subsequent trials (Experiment 1), even when the error is detected (Experiment 2). Moreover, only posterror processes that imply an error correction response produce shift costs (Experiment 3). These results additionally suggest that error detection cannot prevent errors from affecting subsequent performance.     

The Venus effect: people's understanding of mirror reflections in paintings

We propose the term 'Venus effect' for a common phenomenon in picture perception. It occurs when a picture shows an actor and a mirror that are not placed along the observer's line of sight, for instance a Venus admiring herself in a small mirror, and when the actor's reflection in the mirror is visible to the observer. In this situation, observers tend to report, incorrectly, that Venus is also seeing herself in the mirror in the same location as the observer. We discuss this using famous paintings as examples.     

Updating and inhibition processes in working memory: a comparison between Alzheimer's type dementia and frontal lobe focal damage

A large debate has recently focused on the componential nature of the working-memory system (), as evidenced by functional-imaging studies and by using more sophisticated experimental paradigms. The present work aims at further disentangling the role and effects of central executive (CE) and of phonological loop (PL). It is suggested that maintaining active verbal information mostly relates to an intact PL, while the inhibition of interfering information preponderantly involves the CE. To distinguish these effects, two groups of brain damaged patients were administered with an updating task. Frontal lobe patients showed major difficulties in inhibiting interfering information, an ability requiring an involvement of the CE component. In contrast, Alzheimer's dementia patients evidenced a relative impairment in maintaining relevant information, requiring the intervention of the PL.     

Anandamide and memory in CD1 mice: effects of immobilization stress and of prior experience

Five sets of experiments were carried out with CD1 mice tested in a one-trial inhibitory avoidance task. In a first set, immediately posttraining administrations of the endogenous ligand for the cannabinoid CB1 receptor anandamide (arachidonylethanolamide) (3 or 6 mg/kg) dose-dependently impaired memory consolidation in mice. A lower dose (1.5 mg/kg) was ineffective. In a second set of experiments, which was carried out at the same time of the first set, preexposure of the animals to the testing apparatus decreased the effect of the drug, as compared with non-preexposed mice. In a third set of experiments, administration of anandamide (3 or 6 mg/kg) prior to the retention test did not affect the retention performance of mice given posttraining injections of either saline or anandamide. These findings indicate that the memory-impairing effects of posttraining administration of anandamide are not state-dependent. In the fourth and fifth series of experiments, carried out with non-preexposed mice, an otherwise ineffective immobilization stress (15 min) enhanced the memory-impairing effect of anandamide, and an otherwise ineffective dose of naltrexone (0.1 mg/kg) completely antagonized the effect. The results are discussed in terms of attenuation of emotionality, resulting in impaired retention, following anandamide administration, and of involvement of opioid system in the effect of this drug.     

Who owns the contour of a visual hole?

Holes are useful in the study of shape, contour curvature, and border ownership. Several authors have suggested that holes have figural or quasi-figural status. I discuss three criteria to test the evidence that holes behave more like figures than like ground: (i) holes perceived as such; (ii) similar performance for holes and figures; (iii) different performance for holes and other ground regions. Using these criteria, I review the literature and conclude that holes do not have figural status in relation to border ownership. I also argue that holes are ideal stimuli to study figure-ground organisation.     

Detection of change in shape and its relation to part structure

Using a change detection paradigm (Barenholtz, E., Cohen, E. H., Feldman, J., & Singh, M. (2003). Detection of change in shape: An advantage for concavities. Cognition, 89(1) 1-9), we measured sensitivity to the changes of shapes and in particular the difference between detecting a new convex or concave vertex. We conclude that concave vertices per se are not more salient, but changes in the sequence of convexities and concavities along a contour are salient. We argue that these changes are likely to signal a change in perceived part structure.     

Mixing costs in task shifting reflect sequential processing stages in a multicomponent task

We investigated the hypothesis that mixing costs intask shifting reflect th e sequential selection of task components (e.g., stimulus categories) during task execution. This proposition was supported by Hübner, Futterer, and Steinhauser (2001), who showed that the amount of mixing costsdepends on the number of mixed task components (e.g., stimulus level and judgment). However, their results could also be explained by a task set selection account, because task components and task sets were confounded. In Experiments 1 and 2, we compared conditions in which either the number of task sets varied and the number of mixed task components was constant or vice versa. Only the number of mixed task components was predictive for the mixing costs. In Experiment 3, we replicated the additivity of mixing costs from level a ndjudgment mixing. Our results suggest thatthe mixingcosts reflect a selection strategy in which interference is reduced in a stepwise manner.