STOP-IT: Windows executable software for the stop-signal paradigm

The stop-signal paradigm is a useful tool for the investigation of response inhibition. In this paradigm, subjects are instructed to respond as fast as possible to a stimulus unless a stop signal is presented after a variable delay. However, programming the stop-signal task is typically considered to be difficult. To overcome this issue, we present software called STOP-IT, for running the stop-signal task, as well as an additional analyzing program called ANALYZE-IT. The main advantage of both programs is that they are a precompiled executable, and for basic use there is no need for additional programming. STOP-IT and ANALYZE-IT are completely based on free software, are distributed under the GNU General Public License, and are available at the personal Web sites of the first two authors or at expsy.ugent.be/tscope/stop.html.     

Strategy planning in cats (Felis catus) in a progressive elimination task

Domestic cats (Felis cans) were administered a progressive elimination task in which they had to visit and deplete 3 baited sites. Cats were brought back to the starting point after each visit to any site whether the visit represented a correct or an incorrect choice. The results revealed that cats organized search as a function of the least distance principle whether they had to assess starting point to target distances (Experiment 1, n = 12) or adjacent bowl distances (Experiment 2, n = 12). The results also revealed that the starting point to target distance factor was the most influential in determining the initial choice (Experiment 3, n = 6) and in producing errors. Errors were also linked to the antero-posterior bodily axis of the cat. Results are discussed in terms of the predatory behavior of the cat.     

An assessment of response bias for the same-different task: implications for the single-interval task

Two auditory amplitude discrimination experiments were conducted using the same-different experimental design. Observer bias was manipulated, in the first experiment, by varying payoff matrices and, in the second, by varying prior probabilities of signal presentation. Five levels of bias manipulation and four levels of difficulty were employed in each experiment. Each observer received all combinations of bias manipulation and difficulty, but with only one of these combinations within each block of trials. Nine indices of bias were assessed by simultaneously fitting isosensitivity and isobias functions to the data and by fitting isobias functions only. Although none of the indices tested provided an exceptionally good fit to the data, two indices stood out from the rest. These were c*sd and ci, indices with isobias contours similar in shape to those for the c index derived from the yes-no task.     

Decision making and visibility in cats (Felis catus) in a progressive elimination task

When making decisions animals can rely on information stored in memory and/or on information available through perceptual processes. Under some circumstances, perceptual access to a relevant piece of information can be lost as when a prey hides under a cover. If this piece of information is critical, the animal must be able to keep it active in the working memory until the final decision is made. Species endowed with object permanence can to a certain extent overcome such a lack of perceptual access. Numerous studies have investigated object permanence in animals, but no study systematically examined the interaction when making a decision between an information directly available through perception and an information that can no longer be perceived. In the present study, domestic cats (Felis catus) were administered a progressive elimination task in which they had to visit and deplete either two visible and one hidden target (e.g., Experiments 1 and 2) or one visible and two hidden targets (e.g., Experiments 3 and 4). The cats were brought back to the starting point after each visit to any target whether that target had been previously visited or not. The results revealed that the cats searched at the visible target(s) first and at the hidden target(s) last, which was referred to as the visibility rule. The results also revealed that the position of the bowl that was distinct (e.g., the visible bowl when the two other ones were hidden and the opposite) influenced the way this cognitive rule was implemented. More specifically, when the intermediate bowl was distinct the visibility rule was readily implemented but when either the right of the left bowl was distinct the visibility was violated. That is the cats did no longer choose the visible target(s) first. The visibility rule was interpreted in terms of optimization principles, the external distinct target effect was interpreted in terms of divided attention and lateralization.     

An assessment of response bias for thesame-different task: Implications for the single-interval task

Two auditory amplitude discrimination experiments were conducted using thesame-different experimental design. Observer bias was manipulated, in the first experiment, by varying payoff matrices and, in the second, by varying prior probabilities of signal presentation. Five levels of bias manipulation and four levels of difficulty were employed in each experiment. Each observer received all combinations of bias manipulation and difficulty, but with only one of these combinations within each block of trials. Nine indices of bias were assessed by simultaneously fitting isosensitivity and isobias functions to the data and by fitting isobias functions only. Although none of the indices tested provided an exceptionally good fit to the data, two indices stood out from the rest. These werec _sd ^* andc _i, indices with isobias contours similar in shape to those for thec index derived from theyes-no task.     

Tachistoscopic software for the Macintosh

The emulation of a tachistoscope with a Macintosh microcomputer and Pascal language is presented here. The software described is a complete program for the presentation of textual stimuli on the Macintosh screen and includes the recording of reaction times. The stimulus coordinates on the screen are user defined and variable from trial to trial for specific visual angles. The position of a fixation point on the screen and the distance between the subject and the plane of the screen, as well as the particular screen resolution, are taken into account in computing the visual angle.     

The effects of progressive sleep loss on a lexical decision task: Response lapses and response accuracy

A lexical decision task was used in a paradigm testing the effects of sleep loss and fatigue on performance during a 72-h period of sleep deprivation. The data were partitioned into categories of response lapses, response accuracy, and the signal detection measures of discriminability (d’) and bias (β). Response lapses increased as a function of sleep loss and were fitted best by a composite equation with a major linear component and a minor rhythmic component. Response accuracy decreased as a function of sleep loss, with the rate of decrease being greater for nonwords than for words. Although d’ was higher for right visual field (RVF), it decreased for both fields almost linearly as a function of sleep deprivation. The rate of decrease for RVF stimulation was greater than for left visual field (LVF) stimulation, β did not change monotonically as a function of sleep loss, but showed strong circadian rhythmicity, indicating that it was not differentially affected by sleep loss per se.     

New multinomial models for the Chechile-Meyer task

This paper provides a critique of the Chechile and Meyer (J. Math. Psychol. 13 (1976) 269) multinomial processing tree (MPT) models that were generated for the measurement of storage and retrieval components of the correct recall rate. These models were developed for a specific test procedure that involved the random mixing of recall and recognition trials. A key problem with the Chechile and Meyer (J. Math. Psychol. 13 (1976) 269) models is the validity of an assumption made for foil recognition test trials. Three new MPT models for obtaining separate storage and retrieval measures are provided. These new models circumvent the difficulties of the Chechile and Meyer (J. Math. Psychol. 13 (1976) 269) models. Both maximum likelihood estimates (MLE) and population-parameter mapping (PPM) estimates (discussed in Chechile (J. Math. Psychol. 42 (1998) 432)) are provided for the model parameters. Monte Carlo studies were conducted to compare the relative accuracy of the MLE and PPM storage estimates. Both methods have the same average error rate for samples that are very large in size; however, for all the more practical sample sizes, the PPM estimates were more accurate. Statistical methods for model selection were also developed and tested. Finally, the new models were used to reanalyze some existing data. The new analyses provide strong validation evidence for the new models.     

Clarifying the task

Those who would enquire into therelationship between “health conceptions” and “health care consequences” are faced with a formidable task. In order to make this challenge manageable it is necessary to define the scope of the task as precisely as possible. Are we, for instance, faced with a purely theoretical challenge; a task for applied philosophy, or must we employ multi-disciplinary methods? This paper argues that while philosophy has a central clarifying role, inquiry into the relationship between “health conceptions” and “health care organisation” can be done properly only through the combined efforts of several disciplines. Unless we are to be concerned only with abstract models it is essential to take account of the reality of health care situations. Given this it is suggested that the study of “health conceptions” is only a part of a greater task (unless all conceptions are to count as “health conceptions”). What is needed is understanding of the possible and actual purposes of health care, and detailed study of their practical implications.     

Task switching in a hierarchical task structure: evidence for the fragility of the task repetition benefit

This study examined how task switching is affected by hierarchical task organization. Traditional task-switching studies, which use a constant temporal and spatial distance between each task element (defined as a stimulus requiring a response), promote a flat task structure. Using this approach, Experiment 1 revealed a large switch cost of 238 ms. In Experiments 2-5, adjacent task elements were grouped temporally and/or spatially (forming an ensemble) to create a hierarchical task organization. Results indicate that the effect of switching at the ensemble level dominated the effect of switching at the element level. Experiments 6 and 7, using an ensemble of 3 task elements, revealed that the element-level switch cost was virtually absent between ensembles but was large within an ensemble. The authors conclude that the element-level task repetition benefit is fragile and can be eliminated in a hierarchical task organization.     

Tachistoscopic software for the Hercules display controller

The functions necessary for a high-quality microcomputer emulation of a tachistoscope are summarized. A software package containing an extensive set of tachistoscope-emulation functions for IBM PC-type computers is described. This software gives computers equipped with the Hercules monochrome/graphics display controller the ability to produce fast tachistoscopic presentations of text material.     

Evidence for task conflict in the Stroop effect

C. M. MacLeod and P. A. MacDonald (2000) suggested that congruent and incongruent Stroop stimuli cause more task conflict than neutral stimuli because the anterior cingulate cortex is more activated with these stimuli. This study investigated behavioral expression for this pattern. Experiment 1 reduced task conflict control by increasing the proportion of nonword neutrals. Additionally, half the trials had conflict or neutral cues. The control reduction revealed the task conflict. For noncued trials, response time was longer for congruent stimuli than for neutral stimuli (reverse facilitation effect). In addition, response time for congruent stimuli was longer when stimuli were uncued vs. cued. Experiment 2 increased task conflict control by changing the neutral stimuli to noncolor words. Consequently, the task conflict expression disappeared.     

The optimum decision rules for the oddity task

This paper presents the optimum decision rule for an m-interval oddity task in whichm-1 intervals contain the same signal and one is different or odd. The optimum decision rule depends on the degree of correlation among observations. The present approach unifies the different strategies that occur with “roved” or “fixed” experiments (Macmillan & Creelman, 1991, p. 147). It is shown that the commonly used decision rule for anm-interval oddity task corresponds to the special case of highly correlated observations. However, as is also true for thesame-different paradigm, there exists a different optimum decision rule when the observations are independent. The relation between the probability of a correct response andd’ is derived for the three-interval oddity task. Tables are presented of this relation for the three-, four-, and five-interval oddity task. Finally, an experimental method is proposed that allows one to determine the decision rule used by the observer in an oddity experiment.     

Identifying the task characteristics that predict children's construction task performance

Construction tasks form a major part of children's play and can be linked to achievement in maths and science. However there is a lack of understanding of construction task ability and development. Therefore, there is little foundation for the applied use of construction tasks, such as in teaching or research, as there are no apparent methods for assessing difficulty. This empirical research identifies four construction task characteristics that impact on cognition and predict construction task difficulty in children aged 7–8 and 10–11 years and adults. The results also reveal a developmental trajectory in construction ability. The research provides a method to quantify, predict and control the complexity of construction tasks for future research and to inform applied use. Copyright © 2010 John Wiley & Sons, Ltd.     

Windows on the 21st century

Behavior analysis is a cultural system of which the Association for Behavior Analysis is a component cultural system. As cultural systems, they are composed of interlocking behavioral contingencies that constitute their cultural practices. Critical to the survival of both cultural systems is the frequency of interaction with and the nature of the content of the behavioral contingencies composing those cultural practices. The strengths of behavior analysis as a cultural system include its disciplinary character and its worldwide community of scientists and practitioners; its ability to be integrated into a scientific worldview; its track record in providing effective solutions to problems of importance to society; and the high levels of intellect, competence, and commitment that are characteristic of its participants. Weaknesses of behavior analysis are its status as an academic orphan, its relatively small size and its underdeveloped professional identity, and a lack of sociopolitical sophistication among many of its members. Behavior analysis will need to maximize its strengths and mitigate its weaknesses if it is to take advantage of the many opportunities available for growth in the modern world.