The influence of perceptual anchors and visual noise on the vertical-horizontal illusion

In an earlier study Chapanis and Mankin examined the vertical-horizontal illusion in a visually-rich environment. In that study they feit that perceptual anchors and visual noise may have influenced the Ss’ estimates of the real-world objects that were used as stimuli. The present experiment attempted to test in a controlled laboratory environment the questions raised in the previous experiment. In the present experiment Ss were asked to estimate the height of a vertical stimulus line by indicating its corresponding horizontal distance. The vertical stimulus line was presented in a background of visual noise and potential anchors. The results indicate that the anchors did influence estimates and that this influence was, in turn, affected by the visual noise.     

Cognitive load effects on early visual perceptual processing

Contrast-based early visual processing has largely been considered to involve autonomous processes that do not need the support of cognitive resources. However, as spatial attention is known to modulate early visual perceptual processing, we explored whether cognitive load could similarly impact contrast-based perception. We used a dual-task paradigm to assess the impact of a concurrent working memory task on the performance of three different early visual tasks. The results from Experiment 1 suggest that cognitive load can modulate early visual processing. No effects of cognitive load were seen in Experiments 2 or 3. Together, the findings provide evidence that under some circumstances cognitive load effects can penetrate the early stages of visual processing and that higher cognitive function and early perceptual processing may not be as independent as was once thought.     

Differential effects of a visual illusion on online visual guidance in a stable environment and online adjustments to perturbations

In the reported, experiment participants hit a ball to aim at the vertex of a Müller–Lyer configuration. This configuration either remained stable, changed its shaft length or the orientation of the tails during movement execution. A significant illusion bias was observed in all perturbation conditions, but not in the stationary condition. The illusion bias emerged for perturbations shortly after movement onset and for perturbations during execution, the latter of which allowed only a minimum of time for making adjustments (i.e., approx.170 ms). These findings indicate that allocentric information is exploited for online control when people make rapid adjustments in response to a sudden change in the environment and not when people guide their limb movements to interact with a stable environment.     

Comparing the sensitivity of manual pursuit and perceptual judgments to pictorial depth effects

Abstract - We examined whether a pictorial depth illusion influences the manual pursuit of a moving dot to the same extent that it influences the dot's apparent displacement. Fourteen subjects performed two tasks. In one case, they used their unseen hand to track a dot that moved on an elliptical path. In the other, they first watched the dot move on the same path, and then set an ellipse to match the shape of the dot's path. The illusion influenced the two tasks to the same extent, suggesting that the visual information processing is the same for the two tasks.     

Assimilation and contrast in perceptual judgments

An attempt is made to specify the differential conditions underlying two opposite context effects: assimilation and contrast. Assimilation occurs when the judgment of the current stimulus shifts in the direction of the preceding stimulus; contrast occurs when the judgment shifts in the opposite direction. Both effects are brought together and demonstrated in a single paradigm. It is hypothesized that the number of contextual stimuli is the differentiating factor. Two alternative hypotheses, the differential stimulation hypothesis and the temporal position hypothesis, are also tested. The differential stimulation hypothesis proposes that the intensity difference between the contextual and judged stimulus determines whether assimilation or contrast occur, and the temporal position hypothesis proposes that varying the temporal position of the contextual stimulus is the critical factor. While the results do not support either of these alternative hypotheses, it is shown that the number of contextual stimuli does determine whether assimilation or contrast occur.     

Musical expertise modulates the effects of visual perceptual load

Several studies have demonstrated that faces are processed differently from other types of objects, implicating a special role that faces have within the human visual system. However, other studies have suggested that faces may be special only in that they constitute a highly familiar category of visual objects with which most humans have expertise. In this study, we tested a group of expert musicians with a musical instrument classification task during which irrelevant images of musical instruments were presented as visual distractors under varying conditions of perceptual load. Unlike nonmusicians (who had been tested in Lavie, Ro, & Russell, 2003, using the same paradigm as in the present study), the musicians processed these irrelevant images of musical instruments even under conditions of high perceptual load. These results suggest that musical instruments are processed automatically and without capacity limits in subjects with musical expertise and implicate a specialized processing mechanism for objects of high familiarity.     

The peripheral drift illusion: a motion illusion in the visual periphery

Circularly repeating patches containing sawtooth luminance gradients produce a sensation of motion when viewed in the periphery. Illusory motion is perceived in a dark-to-light direction, but only when one's gaze is directed to different locations around the stimulus, a point outside the display is fixated and the observer blinks, or when the stimulus is sequentially displayed at different locations whilst the observer fixates one point. We propose that the illusion is produced by the interaction of three factors: (i) introducing transients as a result of eye movements or blinks; (ii) differing latencies in the processing of luminance; and (iii) spatiotemporal integration of the differing luminance signals in the periphery.     

The effects of list composition and perceptual fluency on judgments of learning (JOLs)

The perceptual fluency hypothesis proposes that items that are easier to perceive at study will be given higher memorability ratings, as compared with less fluent items. However, prior research has examined this metamemorial cue primarily using mixed-list designs. Furthermore, certain memory effects are moderated by the design (mixed list vs. pure list) used to present stimuli. The present study utilized mixed as well as pure lists to assess whether judgments of learning based on perceptual fluency are relative or absolute and whether people are sensitive to differences in recall produced by variation in list composition. Using font size and generation manipulations, Experiments 1 and 2 showed that the effect of perceptual fluency on metamemory is relative in nature, occurring only in mixed lists. Experiments 2 and 3 revealed that metamemory is insensitive to the effect of list composition on recall. These findings are consistent with the assumptions of Koriat’s (Journal of Experimental Psychology: General 126: 349-370, 1997) cue-utilization framework, that JOLs reflect a comparative process and are insensitive to cues pertaining to conditions of learning.     

Primacy and frequency effects in absolute judgments of visual velocity

In absolute judgment tasks, identical stimuli are rated higher (or lower) when presented in a series of more frequent small (or large) stimuli. Using visual stimuli differing in velocity, we show that this conventional frequency effect is largely modulated by the primacy effect--that is, by the stimuli occurring on the early trials of a run. In Experiment 1, a frequency-like primacy effect was obtained with equal-frequent velocities. Identical velocities were rated faster when mainly slow rather than fast ones occurred on initial trials. In Experiment 2, we contrasted the frequency effect and the primacy effect: In runs with frequent slow velocities, mainly fast ones occurred earlier, whereas in runs with infrequent slow velocities, mainly slow ones did so. Lack of differences of ratings in the two conditions suggests that the two effects canceled each other. In Experiment 3, when mainly frequent velocities occurred earlier, the conventional frequency effect was obtained. We conclude that the conventional frequency effect represents a combination of the primacy effect and the pure frequency effect.     

Body-based perceptual rescaling revealed through the size-weight illusion

An embodied approach to the perception of spatial layout contends that the body is used as a 'perceptual ruler' with which individuals scale the perceived environmental layout. In support of this notion, previous research has shown that the perceived size of objects can be influenced by changes in the apparent size of hand. The size-weight illusion is a well known phenomenon, which occurs when people lift two objects of equal weight but differing sizes and perceive that the larger object feels lighter. Therefore, if apparent hand size influences perceived object size, it should also influence the object's perceived weight. In this study, we investigated this possibility by using perceived weight as a measure and found that changes in the apparent size of the hand influence objects' perceived weight.     

Effects of perceptual fluency on judgments of truth.

Statements of the form "Osorno is in Chile" were presented in colors that made them easy or difficult to read against a white background and participants judged the truth of the statement. Moderately visible statements were judged as true at chance level, whereas highly visible statements were judged as true significantly above chance level. We conclude that perceptual fluency affects judgments of truth.     

Acquisition and retention of perceptual learning and the horizontal-vertical illusion.

The present study examined procedure-specific differences in the acquisition and retention of perceptual learning using four forms of the Horizontal-Vertical illusion. Training to criterion was conducted using intertrial feedback, continued visual inspection, or yoked-control procedures. Retention of perceptual learning was assessed at posttraining intervals ranging from 1 minute to 1 month. Subjects trained with feedback achieved criterion in fewer trials and showed greater accuracy and short-term retention of perceptual learning on the inverted-T figure and the 1-in. vertical line-production task. The present results show that the correction of inaccurate strategic factors most likely represents the temporary acquisition of compensatory strategies that facilitate performance on simple perceptual-motor skills tasks.     

Spatial limits on the nonvisual self-touch illusion and the visual rubber hand illusion: Subjective experience of the illusion and proprioceptive drift

The nonvisual self-touch rubber hand paradigm elicits the compelling illusion that one is touching one’s own hand even though the two hands are not in contact. In four experiments, we investigated spatial limits of distance (15 cm, 30 cm, 45 cm, 60 cm) and alignment (0°, 90° anti-clockwise) on the nonvisual self-touch illusion and the well-known visual rubber hand illusion. Common procedures (synchronous and asynchronous stimulation administered for 60 s with the prosthetic hand at body midline) and common assessment methods were used. Subjective experience of the illusion was assessed by agreement ratings for statements on a questionnaire and time of illusion onset. The nonvisual self-touch illusion was diminished though never abolished by distance and alignment manipulations, whereas the visual rubber hand illusion was more robust against these manipulations. We assessed proprioceptive drift, and implications of a double dissociation between subjective experience of the illusion and proprioceptive drift are discussed.     

Subjective confidence in perceptual judgments: a test of the self-consistency model

Two questions about subjective confidence in perceptual judgments are examined: the bases for these judgments and the reasons for their accuracy. Confidence in perceptual judgments has been claimed to rest on qualitatively different processes than confidence in memory tasks. However, predictions from a self-consistency model (SCM), which had been confirmed for general-information questions (Koriat, 2010) and social attitudes (Koriat & Adiv, 2010), are shown to hold true also for perceptual judgments. In SCM, confidence is modeled by the procedure for assessment of statistical level of confidence: For a 2-alternative, forced-choice item, confidence is based on the consistency with which the choice is favored across a sample of representations of the item, and acts as a monitor of the likelihood that a new sample will yield the same choice. Assuming that these representations are drawn from commonly shared populations of representations associated with each item, predictions regarding the basis of confidence were confirmed by results concerning the functions relating confidence and choice latency to interparticipant consensus and to intraparticipant consistency for majority and minority choices. With regard to the confidence-accuracy (C/A) relationship, the consensuality principle, documented for general-knowledge tasks (Koriat, 2008a), was replicated for perceptual judgments: Confidence correlated with the consensuality of the choice rather than with its correctness, suggesting that the C/A correlation is due to the relationship between confidence and self-consistency and is positive only as long as the correct choices are the consistently made choices. SCM provides a general model for the basis and accuracy of confidence judgments across different domains.