Visual causal impressions in the perception of several moving objects

Several kinds of visual causal impressions occur when people observe stimuli involving objects in motion. It is hypothesized that these impressions occur when the visual system avoids coincidences by matching the observable kinematic features of the stimulus to a template of a physical mechanism. This was tested by constructing a stimulus in which several spatially separated objects move in a coordinated manner. Variations on this stimulus were constructed such that some were inconsistent with a possible physical mechanism that could explain the motions of the objects and others were consistent with it. Mechanism‐inconsistent variations yielded significantly lower ratings of the causal impression and mechanism‐consistent variations did not, supporting the hypothesis. Misperceptions of features of the stimulus were also reported by a majority of participants, and the nature of these misperceptions is also consistent with the hypothesis that the stimulus is interpreted as a representation of a kind of physical mechanism.     

Initiation of bilateral responses in a kinesthetic reaction time task

Two experiments are presented in which different mechanisms controlling each limb in a bilateral arm response to a unilateral kinesthetic stimulus are postulated to occur. In Experiment 1, the limb serving as the stimulus are postulated to occur. In Experiment 1, the limb serving as the stimulus limb was described as operating with relative invariance by using a tightly coupled input-output reflexive pathway, whereas the nonstimulus limb appeared to be controlled by higher-order processing thought to be more susceptible to influences such as hemispheric specialization and stimulus expectancy. The differential control model was further tested in Experiment 2 by retaining the interhemispheric pathway of the unilateral kinesthetic stimulus but experimentally uncoupling the reflex mechanism from the stimulus side. Analyses of bilateral EMG premotor latencies under these conditions revealed that each response side can be controlled at separate levels-i.e., by a reflexive type mechanism or by higher-order processing when one of the response limbs is also the stimulus limb, both sides reflect behavior that is best described by an information processing type of voluntary control.     

Control of reflexive and voluntary saccades in the gap effect

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism, Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array—a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.     

Control' of reflexive and voluntary saccades in the gap effect.

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism. Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array--a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.     

Selective mechanisms in visual perception

The notion of perceptual tuning is investigated by presenting alternatives either before, after, or both before and after a tachistoscopic stimulus. Study 1 (N = 12) showed that identification accuracy is best with alternatives both before and after the stimulus, poorest with alternatives after the stimulus, and intermediate with alternatives only before the stimulus. Study 2 (N = 3) indicated that performance with alternatives both before and after the stimulus varies according to where S is permitted to fixate prior to each exposure. The possibility of a central tuning mechanism was not strongly supported.     

Initiation of Bilateral Responses in a Kinesthetic Reaction Time Task

Two experiments are presented in which different mechanisms controlling each limb in a bilateral arm response to a unilateral kinesthetic stimulus are postulated to occur. In Experiment 1, the limb serving as the stimulus limb was described as operating with relative invariance by using a tightly coupled input-output reflexive pathway, whereas the nonstimulus limb appeared to be controlled by higher-order processing thought to be more susceptible to influences such as hemispheric specialization and stimulus expectancy. The differential control model was further tested in Experiment 2 by retaining the intrahemispheric pathway of the unilateral kinesthetic stimulus but experimentally uncoupling the reflex mechanism from the stimulus side. Analyses of bilateral EMG premotor latencies under these conditions revealed that each response side can be controlled at separate levels —i.e., by a reflexive type mechanism or by higher-order processing when one of the response limbs is also the stimulus limb. When the stimulus is on the same side but not generated by either responding limb, both sides reflect behavior that is best described by an information processing type of voluntary control.     

Noise exclusion in spatial attention

Precue validity affects the performance of perceptual tasks. These spatial attention effects have been variously attributed to facilitation of processing, capacity allocation, or noise reduction. We used a new attention-plus-external (stimulus)-noise paradigm and model to identify the mechanisms of attention in cue-validity paradigms. A new phenomenon is reported: a large effect of location cue validity in an orientation identification task that specifically occurs when the stimulus is embedded in external (environmental or stimulus) noise. This result identifies the mechanism of the effect as external-noise exclusion, distinguished from stimulus enhancement that manifests itself only in noiseless stimulus environments.     

Conditioning of the microcirculation in the rat

The serotonin-catecholamine balancing mechanism maintains normal vascular tonus and permeability of the microcirculation. Serotonin provokes local vasodilatation and increases capillary permeability in the skin of rats. Released or injected catecholamines inhibit the serotonin-induced peripheral hemodynamic alterations. Following eleotroconvulsive treatment (ECT) (US), there is a catecholamine release and the microcirculatory response to serotonin does not occur. When the administration of a visual stimulus (in six consecutive occasions) proceedingly coincided with the administration of the ECT, it was noted that the light became an effective stimulus for this system. Light alone is an indifferent stimulus to catecholamine release. Thus, the inhibition of the serotonin-induced vasodilatation by ECT (via catecholamine release) became conditioned to the visual-conditional stimulus. Since the net effect of extrinsic serotonin depends on free catecholamines at the vascular bed, the intensity of the serotonin-induced vascular response reflects alterations in the chemical balancing mechanism. This mechanism can be conditioned with the present technique. The result indicates that there is central nervous system mediation.     

Visible persistence following a brief increment in stimulus luminance

In previous studies, it has been demonstrated that visible persistence--the period for which the perceived duration of a stimulus exceeds its physical duration--can be extended by briefly incrementing the luminance of the stimulus immediately prior to offset. Using a two-component pattern integration task, we show that this effect is not an artifact of change in the total luminous flux within the stimulus. Visible persistence was unaffected by overall luminance of the stimulus. It was also time-locked to the luminance increment. Visible persistence is seen to result from a process that is initiated by stimulus onset and that can be either wholly or partially reinitiated by the onset of the luminance increment. The duration of this process (which determines the duration of stimulus visibility) can be modified in a graded fashion by stimulus events that occur after its initiation. We outline a single-process inhibitory feedback model of the persistence mechanism that accounts for the present findings.     

Learned changes in the sensitivity of stimulus representations: Associative and nonassociative mechanisms

Central to associative learning theory is the proposal that the concurrent activation of a pair of event representations will establish or strengthen a link between them. Associative theorists have devoted much energy to establishing what representations are involved in any given learning paradigm and the rules that determine the degree to which the link is strengthened. They have paid less attention to the question of what determines that a representation will be activated, assuming, for the case of classical conditioning, that presentation of an appropriately intense stimulus from an appropriate modality will be enough. But this assumption is unjustified. Ipresent the results of experiments on the effects of stimulus exposure in rats that suggest that mere exposure to a stimulus can influence its perceptual effectiveness—that the ability of a stimulus to activate its representation can be changed by experience. This conclusion is of interest for two reasons. First, it supplies a direct explanation for the phenomenon of perceptual learning—the enhancement of stimulus discriminability produced by some forms of stimulus exposure. Second, it poses a theoretical challenge in that it seems to require the existence of a learning mechanism outside the scope of those envisaged by current formal theories of associative learning. I offer some speculations as to how this mechanism might be incorporated into such theories.     

An inhibition effect in the temporal constrains of attentional selection: the Backward Blink

The study aims at investigating the dynamics of visual information processing during sequential control of attentional selection. By combining two different traditional paradigms we show for the first time that during rapid selection of visual targets, encoding of a new target stimulus is facilitated by suppression of the preceding relevant stimulus category (Backward Blink; BB). Such inhibition would operate to reduce interference from previously stored information, in order to facilitate the instantiation of a new attentional episode. Results suggest that the same underlying inhibitory mechanism might contribute to two different attentional effects, specifically, the switch cost and the Attentional Blink, suggesting a general inhibitory mechanism of attentional control, with broad implications for understanding how the brain perceives any task-relevant stimulus.     

A note on behavioural contrast and frustration

The suggestion has been made that positive contrast, the increase in response rate in one successively-presented stimulus following a change in conditions that decreases responding in the other, may not depend on differential stimulus control. Evidence is reviewed suggesting that contrast effects on most multiple interval schedules do depend upon discrimination, but that effects similar to contrast that result from the omission of reinforcement on fixed-interval schedules (the frustration/omission effect) reflect other factors. The link between contrast and the omission effect is the discrimination mechanism which allows animals to respond only at times or places correlated with food delivery. Contrast is a direct result of this mechanism; but the omission effect depends on the difference between the inhibitory discriminative after-effects acquired by food on fixed-interval schedules, and those acquired by a “neutral” stimulus presented in its place.     

情绪诱发的视盲：一种独特的功能性视盲

功能性视盲是指由于某种原因导致正常的视觉系统出现视觉觉察丧失的现象, 例如变化知盲、注意瞬脱等都属于功能性视盲。情绪诱发的视盲指的是一个与任务无关的情绪性刺激的呈现吸引了注意以致个体无法对快速呈现的靶刺激有所觉察的现象。与注意瞬脱特别是情绪性注意瞬脱相比, 情绪诱发的视盲是以情绪刺激为干扰刺激, 考察情绪刺激如何以自下而上的方式吸引注意并干扰靶刺激的加工, 因此有着自己的特点：它没有lag1节省现象, 也没有像注意瞬脱那样严格的时间窗口限制, 不受干扰刺激与靶刺激物理特征相似程度的限制, 在心理机制上属于早期知觉阶段的加工竞争等等。情绪诱发的视盲表明情绪对注意在时间和空间两个维度上都有吸引或干扰作用。未来可以从考察神经机制、了解影响因素等多方面深化此领域的研究。     

Dissipation of retroactive interference in human infants

In 3 experiments with 85 human 3-month-olds, the authors asked whether retroactive interference with their memory of the original training stimulus is temporary or permanent. Infants learned to move a mobile by kicking and then were exposed to a different mobile (Experiment 1) or context (Experiment 2) immediately or 3 days afterward (Experiment 3). They were tested after increasing delays with the original stimulus, the exposed stimulus, or a completely novel stimulus. Retroactive interference was temporary and unrelated to the exposure delay. The data are consistent with a retrieval-based account of interference. Memory updating (i.e., responding to the interfering stimulus) was coincident with retroactive interference, suggesting that retroactive interference is an adaptive mechanism that facilitates memory updating within a narrow time window.     

Encoding processes in memory scanning tasks

Three experiments are presented that deal with the effect of stimulus probability on the encoding of both alphanumeric characters and nonsense figures. Experiment I replicated a previous finding of an interaction between stimulus probability and stimulus quality in a memory scanning task with numbers as stimuli. Experiments II and III investigated the same paradigm with unfamiliar visual forms as stimuli, and no interaction was found. Results were interpreted as showing that probability affects the encoding mechanism only when the encoding process results in a representation of the name of the stimulus. When stimulus materials are visual forms without names, probability does not appear to affect encoding processes.     

On Stimulus Generalization and Stimulus Classes

Stimulus generalization has been defined as the spread of effect of reinforcement for responses emitted in the presence of one stimulus to different stimuli presented under extinction conditions. As a result of stimulus generalization, novel stimuli come to exert stimulus control over members of the response class. Studies in the applied behavior analysis literature, however, have reported experimental preparations that included prompting and reinforcement procedures during what were claimed to be stimulus generalization conditions. These studies violated the procedural requirement that stimulus generalization be tested under extinction conditions. Responses that come under the control of a class of stimuli may do so by direct training or by stimulus generalization. It is desirable for organisms to respond in the presence of members of an appropriately constructed stimulus class, but we should understand the mechanism of entry into the class by its members. If inaccurate claims of stimulus generalization are made when training procedures are used in the ostensible generalization conditions, the robustness of the original training procedures will be over estimated. By adhering to the operational requirements of behavioral definitions, we could better understand the power and limits of our educational and training procedures.     

Preconditioning of reinforcing properties to an exteroceptive feedback stimulus

Three groups of rats were given Pavlovian preconditioning by means of a yoking procedure and subsequently trained to avoid. One group received a light stimulus during preconditioning at the same times as the master avoiding animals received an exteroceptive feedback stimulus. During the subsequent avoidance training, this group was then given the same light stimulus as a feedback stimulus on successful avoidance trials. The group learned two-way avoidance in about the same number of trials as one-way avoidance is typically learned and substantially faster than two other control groups. These data indicate that feedback stimuli develop reinforcing properties by a Pavlovian mechanism. The data of the control groups indicate that feedback stimuli do not provide “information” about responding in the present situation.     

Vernier offset produced by rotary target motion

Two separated colinear lines appear displaced from colinearity when either the target or the subject’s head is rotated in a frontal plane. The direction of perceived offset is reversed for opposite directions of rotation. The present experiments prove that the effect depends on some property of the visual system that is responsive to stimulus motion per se and is not manifested in the response to stationary targets. Two mechanisms which may be responsible for the rotation-contingent effect are considered: (1) An induction mechanism based on the dynamics of induced tilt or of figural aftereffect displacement. (2) A mechanism based on variation of visual latency with stimulus energy/time.     

Position uncertainty and the perception of apparent movement

Two experiments compared the perception of apparent movement when the second of two successive stimuli always appeared in the same position and when it varied randomly between two spatial positions. The results of both experiments showed that foreknowledge of the position of the second stimulus does not facilitate the perception of apparent movement. Experiment 2 also clearly showed that the space-time relationships of Korte’s third law of apparent movement does not depend on foreknowledge of the position of the second stimulus. These findings imply that apparent movement in real time occurs after the second stimulus has been registered by the visual system. It suggests that apparent movement involves a delayed decision mechanism that stores the first stimulus, the interstimulus temporal interval, and the second stimulus, and then impletes a motion compatible with the stimulus information.