Natural sampling and base-rate neglect

Using an analogue of the lawyer-and-engineer item (Kahneman & Tversky, 1973), we compared conditions in which base rates were either presented as percentages (A), or frequencies (B), to conditions in which the natural sampling process was described additionally (C) or was directly experienced (D). We expected the likelihood of base-rate utilization to increase as the presentation approaches the process of natural sampling. Accordingly, results showed that the contingency of judgments on base rates systematically increased across conditions A to D. © 1998 John Wiley & Sons, Ltd.     

The environmental malleability of base-rate neglect

Psychonomic Bulletin & Review - Across two experiments (N=799) we demonstrate that people’s use of quantitative information (e.g., base-rates) when making a judgment varies as the causal...     

Teaching pigeons to commit base-rate neglect

Whereas humans display base-rate neglect in a behavioral analogue of the base-rate problem, pigeons have been shown to behave optimally in a comparable task, appropriately weighting base-rate and case-cue information. Previous studies have shown that prior experience may interfere with optimal decisions for human subjects, a result consistent with the position that poor and illogical decisions often follow from the misapplication of learned rules. The present study shows that pigeons will also display base-rate neglect if given extensive pretraining with informative case cues. Two experiments with pigeons, in a matching-to-sample procedure designed to mimic the classic base-rate problem, show that pigeons display base-rate neglect after extensive pretraining with the matching task.     

Memory mechanisms in pigeons: evidence of base-rate neglect

In delayed matching to sample, once acquired, pigeons presumably choose comparisons according to their memory for (the strength of) the sample. When memory for the sample is sufficiently weak, comparison choice should depend on the history of reinforcement associated with each of the comparison stimuli. In the present research, pigeons acquired two matching tasks in which Sample S1 was associated with one comparison from each task, C1 and C3, whereas Sample S2 was associated with Comparison C2, and Sample S3 was associated with Comparison C4. As the retention interval increased, the pigeons showed a bias to choose the comparison (C1 or C3) associated with the more frequently occurring sample (S1). Thus, pigeons were sensitive also to the (irrelevant) likelihood that each of the samples was presented. The results suggest that pigeons may allow their reference memory for the overall sample frequency to influence comparison choice, independent of the comparison stimuli present.     

心理距离对基线比例忽略的影响

基线比例忽略是指在不确定情境中, 个体进行判断和决策时不能充分利用或者忽略基线比例的现象。本研究通过系列情境实验探索了三种不同维度的心理距离, 即时间距离、空间距离和社会距离对基线比例忽略的影响。结果发现, 三种心理距离均能够对基线比例忽略产生影响：当时间距离、空间距离和社会距离较近时, 个体更容易表现出基线比例忽略现象; 而当时间距离、空间距离和社会距离较远时, 个体的基线比例忽略倾向减弱。     

Base-rate neglect as a function of base rates in probabilistic contingency learning

When humans predict criterion events based on probabilistic predictors, they often lend excessive weight to the predictor and insufficient weight to the base rate of the criterion event. In an operant analysis, using a matching-to-sample paradigm, Goodie and Fantino (1996) showed that humans exhibit base-rate neglect when predictors are associated with criterion events through physical similarity. In partial replications of their studies, we demonstrated similar effects when the predictors resembled the criterion events in terms of similarly skewed base rates. Participants' predictions were biased toward the more (or less) frequent criterion event following the more (or less) frequent predictor. This finding adds to the growing evidence for pseudocontingencies (Fiedler & Freytag, 2004), a framework that stresses base-rate influences on contingency learning.     

Reducing neglect by introducing ipsilesional global cues

Halligan and Marshall (1994) have proposed that unilateral neglect (UN) can be reduced by ipsilesional global cues which induce processing of the whole object, including contralesional features. This hypothesis has the potential to distinguish difficulties with disengaging attention after ipsilesional capture from the failure of contralesional stimuli to capture attention. To test the role of global cues, seven individuals with unilateral right-hemispheric lesions copied and verbally identified drawings adapted from Seron, Coyette, and Bruyer (1989). The level of meaningful information presented in the ipsilesional hemispace was varied across three levels: symmetrical objects, objects with an identifying left-side feature, and objects that required processing of the left-side information for plausible identification. The results support the global processing hypothesis by demonstrating that the less the ipsilesional information, the less was the neglect of contralesional information.     

Positional acuity without monocular cues

The accuracy with which human observers can determine the spatial location of a shape boundary was measured by vernier alignment. The vernier targets were presented as random-dot stereograms, with varying amounts of camouflage in the monocular image. Camouflage decreased vernier acuity, but when the camouflage was broken by stereoscopic disparity, acuity was improved. In the limiting case when the shape boundaries were defined by disparity information alone, vernier thresholds (75% correct, binary forced-choice) were in the region of 40 s visual angle. This is poor acuity in comparison to vernier thresholds with monocular contour, but if the limited resolution acuity for stereopsis is taken into account, cyclopean and monocular positional acuities can be considered quite similar in relation to their respective resolution limits.     

Bimanual training reduces spatial interference

The authors investigated whether training can reduce bimanual directional interference by using a star-line drawing paradigm. Participants (N = 30) were required to perform rhythmical arm movements with identical temporal but differing directional demands. Moreover, the effectiveness of part-task training in which each movement was practiced in isolation was compared with that of whole-task training in which only combined movements were performed. Findings revealed that bimanual training substantially reduced spatial interference, but unimanual training did not. The authors therefore concluded that the spatial coupling of the limbs is not implemented in a rigid way; instead, the underlying neural correlate can undergo plastic changes induced by training. Moreover, the practical implication that emerged from the present study is that athletic, musical, or ergonomic skills that require a high degree of interlimb coordination are best served by whole-task practice.     

A case study of expert judgment: Economists' probabilities versus base-rate model forecasts

In this case study of economists' forecasts concerning economic downturn, we examine key issues concerning the psychology of prediction and the controversy surrounding the value of expertise in forecasting. We examine when experts' knowledge promotes forecast accuracy and whether biases found in psychological studies (including underutilization of relevant base rates and tendencies to extreme prediction) occur in these economic forecasts. Experts' forecasts were compared to forecasts derived from base-rate models that relied on the historical frequencies of economic downturns. The performance patterns of the experts and models crossed over the forecast horizon. Experts outperformed models in shorter-term forecasting, whereas models outperformed experts in longer-term forecasting. These results highlight the abilities and limits of experts and models in prediction and the sources of their inaccuracy.     

Effects of training on attention to acoustic cues

Learning new phonetic categories in a second language may be thought of in terms of learning to focus one's attention on those parts of the acoustic-phonetic structure of speech that are phonologically relevant in any given context. As yet, however, no study has demonstrated directly that training can shift listeners' attention between acoustic cues given feedback about the linguistic phonetic category alone. In this paper we discuss the results of a training study in which subjects learned to shift their attention from one acoustic cue to another using only category-level identification as feedback. Results demonstrate that training redirects listeners' attention to acoustic cues and that this shift of attention generalizes to novel (untrained) phonetic contexts.     

A virtual reality assessment and training system for unilateral neglect.

Patients with unilateral neglect have problems reporting, responding, or orienting to novel or meaningful stimuli that is presented to the side opposite to that of a brain lesion. This creates a serous problem in regards to daily living activities. However, the established methods for assessing and training of unilateral neglect patients have several deficits. Recently, virtual reality (VR) technologies have been used as an assessment and treatment tool for rehabilitation. Hence, this study designed a VR system to assess and train unilateral neglect patients. In addition, the suitability and feasibility of our VR system for unilateral neglect patients was verified.     

Rapid eye-fixation training without eyetracking

Maintenance of stable central eye fixation is crucial for a variety of behavioral, electrophysiological, and neuroimaging experiments. Naive observers in these experiments are not typically accustomed to fixating, either requiring the use of cumbersome and costly eyetracking or producing confounds in results. We devised a flicker display that produced an easily detectable visual phenomenon whenever the eyes moved. A few minutes of training using this display dramatically improved the accuracy of eye fixation while observers performed a demanding spatial attention cuing task. The same amount of training using control displays did not produce significant fixation improvements, and some observers consistently made eye movements to the peripheral attention cue, contaminating the cuing effect. Our results indicate that (1) eye fixation can be rapidly improved in naive observers by providing real-time feedback about eye movements, and (2) our simple flicker technique provides an easy and effective method for providing this feedback. S. Suzuki, satoru@northwestern.edu     

Transcranial alternating brain stimulation at alpha frequency reduces hemispatial neglect symptoms in stroke patients

Background/ObjectiveNon-invasive brain stimulation techniques such as transcranial alternating current stimulation (tACS) may help alleviate attention deficits in stroke patients with hemispatial neglect by modulating oscillatory brain activity. We applied high-definition (HD)-tACS at alpha frequency over the contralesional hemisphere to support unilateral oscillatory alpha activity and correct for the pathologically altered attention bias in neglect patients.MethodsWe performed a within-subject, placebo-controlled study in which sixteen stroke patients with hemispatial neglect underwent 10 Hz (alpha) as well as sham (placebo) stimulation targeting the contralesional posterior parietal cortex. Attentional bias was measured with a computerized visual detection paradigm and two standard paper-and-pencil neglect tests.ResultsWe revealed a significant shift of attentional resources after alpha-HD-tACS, but not sham tACS, toward the ipsilateral and thus contralesional hemifield leading to a reduction in neglect symptoms, measured with a computerized visual detection paradigm and a widely used standard paper and pencil neglect tests.ConclusionsWe showed a significant alpha-HD-tACS-induced shift of attentional resources toward the contralesional hemifield, thus leading to a reduction in neglect symptoms. Importantly, HD-tACS effects persisted after the stimulation itself had ended. This tACS protocol, based on intrinsic oscillatory processes, may be an effective and well-tolerated treatment option for neglect.     

Motion direction discrimination training reduces perceived motion repulsion

Participants often exaggerate the perceived angular separation between two simultaneously presented motion stimuli, which is referred to as motion repulsion. The overestimation helps participants differentiate between the two superimposed motion directions, yet it causes the impairment of direction perception. Since direction perception can be refined through perceptual training, we here attempted to investigate whether the training of a direction discrimination task changes the amount of motion repulsion. Our results showed a direction-specific learning effect, which was accompanied by a reduced amount of motion repulsion both for the trained and the untrained directions. The reduction of the motion repulsion disappeared when the participants were trained on a luminance discrimination task (control experiment 1) or a speed discrimination task (control experiment 2), ruling out any possible interpretation in terms of adaptation or training-induced attentional bias. Furthermore, training with a direction discrimination task along a direction 150° away from both directions in the transparent stimulus (control experiment 3) also had little effect on the amount of motion repulsion, ruling out the contribution of task learning. The changed motion repulsion observed in the main experiment was consistent with the prediction of the recurrent model of perceptual learning. Therefore, our findings demonstrate that training in direction discrimination can benefit the precise direction perception of the transparent stimulus and provide new evidence for the recurrent model of perceptual learning.     

Do smokers devaluate smoking cues after go/no-go training?

Objective: Smoking is one of the leading public health problems worldwide. The inability to quit smoking may be the result of the amplified value of smoking-related cues and inhibitory control deficits. Previous research has shown that pairing substance-related cues with no-go trials in go/no-go training reduces the value of these cues, an effect known as devaluation. The current experiment investigated the devaluation effect of go/no-go training on smoking-related cues, and compared this effect between smokers and nonsmokers.

Design and Main Outcome Measures: 39 smokers and 43 nonsmokers were trained to respond immediately to neutral stimuli, but inhibit their reaction when smoking stimuli were presented. Before and after training, participants evaluated smoking and neutral stimuli, where part of these stimuli were subsequently presented in the training, and the other part was not used in training.

Results: Not responding to smoking stimuli in go/no-go training decreased subsequent evaluations of trained smoking stimuli compared to untrained smoking stimuli, thereby replicating food and alcohol studies and extending the devaluation effect to smoking-related cues. This devaluation effect was found for both smokers and non-smokers.

Conclusion: Smoking-related cues can be devaluated in smokers and non-smokers, thereby showing the potential for Go/No-Go training in smoking cessation interventions.     

Configural learning without configural training.

Rats learned discriminations in which 2 familiar compound visual stimuli AB and CD were nonreinforced, whereas less-familiar compounds (EF, GH, IJ...) were reinforced (constant-negative paradigm). Such discriminations can in principle be acquired through elemental (nonconfigural) learning. Three different types of compound--object/object, object/position, and shape/fill-pattern--were used, and the number of familiar compounds extended to 3 or 4. In all cases, when rats were tested for the first time with previously unseen recombinations of the familiar elements--for example, AC, BD--they preferred these to the familiar compounds, implying that they had encoded configural information during the original training. Moreover, preference remained constant despite extended exposure to configural training in the test phase. The findings extend the evidence that configural representations are formed independently of explicit configural training.     

Veering re-visited: noise and posture cues in walking without sight

Effects of sound and posture cues on veering from the straight-ahead were tested with young blind children in an unfamiliar space that lacked orienting cues. In a pre-test with a previously heard target sound, all subjects walked straight to the target. A recording device, which sampled the locomotor trajectories automatically, showed that, without prior cues from target locations, subjects tended to veer more to the side from which they heard a brief, irrelevant noise. Carrying a load on one side produced more veering to the opposite side. The detailed samples showed that, underlying the main trajectories, were alternating concave and convex (left and right) movements, suggesting stepwise changes in body position. It is argued that the same external and body-centred cues that contribute to reference-frame orientation for locomotion when they converge and concur, influence the direction of veering when the cues occur in isolation in environments that lack converging reference information.