Spatial and temporal lightness anchoring

Research in the area of lightness perception has not adequately addressed the influence of previously viewed visual fields on perceived surface reflectance. In the spatial realm, a spot-in-a-void will appear darker when a second surface of higher intensity is placed adjacent to it. The brighter surface takes the role of white, the anchor, and the dimmer is scaled accordingly. We find that when a spot-in-a-void is presented to observers in a light controlled chamber it is influenced by nonretinal temporal relationships mediated by the degree of complexity. We also find that the influence cannot be explained in terms of successive contrast at a high or low level in the visual system, but can be explained by an anchoring model. The present results follow the same rules governing spatial integration and anchoring and thereby support the currently proposed concept of temporal anchoring.     

Simultaneous lightness contrast on plain and articulated surrounds

Simultaneous lightness contrast is stronger when the dark and light backgrounds of the classic display (where one of the targets is an increment and the other is a decrement) are replaced by articulated fields of equivalent average luminances. Although routinely attributed to articulation per se, this effect may simply result from the increase in highest luminance in the light articulated, vs plain, background; by locally darkening the decremental target, such an increase would amplify the difference between the targets. We disentangled the effects of highest luminance and articulation by measuring, separately, the magnitude of lightness contrast on dark and light plain and articulated backgrounds. We found that highest luminance and articulation contribute separately to the final illusion.     

When figure-ground segmentation modulates brightness: the case of phantom illumination

In the phantom illumination illusion, luminance ramps ranging from black to white induce a brightness enhancement on an otherwise homogeneous dark background. The strength of the illusion was tested with regard to the extension of the brightness inducing perimeter, surrounding the target area by manipulating the number of inducers (exp. 1) and the size of the inducers (exp. 2). Participants' task was to rate the difference in brightness between the target area and the background. Results show that the illusion occurs only when the target area is not completely segregated from the background by luminance ramps; vice versa, when the target area is delimited by a continuous gradient, it appears darker than the background. These findings suggest a major role of figure-ground organization in the appearance of the illusion. This hypothesis was tested in a rating task experiment with three types of target area shapes circumscribed by four types of edges: luminance contours, illusory contours, no contours, and ambiguous contours. Illusory contours, just as luminance contours, hinder the illusion and produce a darkening of the target area. A control experiment measured the brightness of the previous stimuli without luminance ramps: all configurations resulted in a darkening of the target area. Results from all experiments suggest that figure-ground segmentation plays a major role in the determination of both illumination and lightness in stimuli with luminance gradients.     

Anchoring,Activation, and the Construction of Values

Anchoring is a pervasive judgment bias in which decision makers are systematically influenced by random and uninformative starting points. While anchors have been shown to affect a broad range of judgments including answers to knowledge questions, monetary evaluations, and social judgments, the underlying causes of anchoring have been explored only recently. We suggest that anchors affect judgments by increasing the availability and construction of features that the anchor and target hold in common and reducing the availability of features of the target that differ from the anchor. We test this notion of anchoring as activation in five experiments that examine the effects of several experimental manipulations on judgments of value and belief as well as on measures of cognitive processes. Our results indicate that prompting subjects to consider features of the item that are different from the anchor reduces anchoring, while increasing consideration of similar features has no effect. The anchoring-as-activation approach provides a mechanism for debiasing anchoring and also points to a common mechanism underlying anchoring and a number of other judgment phenomena.     

Lightness from contrast: a selective integration model

As has been observed by Wallach (1948), perceived lightness is proportional to the ratio between the luminances of adjacent regions in simple disk-annulus or bipartite scenes. This psychophysical finding resonates with neurophysiological evidence that retinal mechanisms of receptor adaptation and lateral inhibition transform the incoming illuminance array into local measures of luminance contrast. In many scenic configurations, however, the perceived lightness of a region is not proportional to its ratio with immediately adjacent regions. In a particularly striking example of this phenomenon, called White's illusion, the relationship between the perceived lightnesses of two gray regions is the opposite of what is predicted by local edge ratios or contrasts. This paper offers a new treatment of how local measures of luminance contrast can be selectively integrated to simulate lightness percepts in a wide range of image configurations. Our approach builds on a tradition of edge integration models (Horn, 1974; Land & McCann, 1971) and contrast/filling-in models (Cohen & Grossberg, 1984; Gerrits & Vendrik 1970; Grossberg & Mingolla, 1985a, 1985b). Our selective integration model (SIM) extends the explanatory power of previous models, allowing simulation of a number of phenomena, including White's effect, the Benary Cross, and shading and transparency effects reported by Adelson (1993), as well as aspects of motion, depth, haploscopic, and Gelb induced contrast effects. We also include an independently derived variant of a recent depthful version of White's illusion, showing that our model can inspire new stimuli.     

The effect of feedback on children’s metacognitive judgments: a heuristic account

In three experiments, we investigated whether the feedback effect on the accuracy of children’s metacognitive judgments results from an improvement in monitoring processes or the use of the Anchoring-and-Adjustment heuristic. Experiment 1 revealed that adding feedback increased the accuracy of young children’s (aged 4, 6, and 8 years) memory prediction. In Experiment 2, the influence of an external anchor on children’s metacognitive judgment was established. Finally, in Experiment 3, two memory tasks that differed in terms of difficulty were administered. Participants were randomly assigned to an anchoring (high/low/no anchor) and a feedback (feedback/no feedback) condition. Results demonstrated that children in the feedback condition adjusted their predictions toward the feedback, regardless of the task’s difficulty. These findings are consistent with the hypothesis that external information provided by feedback is used as an anchor for judgment. This interpretation is strengthened by the correlation found between the two scores computed to assess participants’ susceptibility to anchoring and feedback effects, which indicates that children who are more sensitive to the anchoring effect are also more sensitive to the feedback effect.     

Inhomogeneous surrounds, conflicting frameworks, and the double-anchoring theory of lightness

The empirical question of whether or not the lightness of a region is accounted for purely by the average luminance of its surround has a complex answer that depends on whether such a region is an increment, a decrement, or intermediate relative to the luminances of the contiguous surfaces. It is shown here that a new model of lightness, based on anchoring principles, predicts and clarifies such intricacies. In this model, the luminance of the target region determines its lightness in two ways: indirectly, by causing it to group with parts of its surround and thus defining the nested frameworks to which it belongs; and directly, by anchoring it to the highest luminance and to the average surround luminance in each of these frameworks. Inter- and intraindividual differences in lightness assessment are shown to emerge under grouping conditions that create unstable, conflicting frameworks.     

The Semantics of Anchoring

Previous research has demonstrated that judgmental anchoring effects—the assimilation of a numeric estimate to a previously considered standard—are semantic in nature. They result because the semantic knowledge about the target object that is activated during the comparison with the anchor influences the absolute judgment. In addition to this semantic influence, the numeric anchor value itself may also yield an effect under specific conditions. The present research was designed to examine the relative strength of both mechanisms and explore their boundary conditions. Studies 1 and 2 demonstrate that semantic anchoring effects are more potent than purely numeric effects. Study 3 further suggests that purely numeric effects only operate if accessible semantic knowledge is inapplicable to the critical judgment so that semantic influences are incapacitated. The implications of these findings are discussed from the perspective of an integrative model which differentiates between two stages of anchoring. Whereas purely numeric influences appear to be limited to the stage of anchor selection, the actual comparison with the target involves more elaborate semantic processes.     

The role of first- and second-order stimulus features for human overt attention

When processing complex visual input, human observers sequentially allocate their attention to different subsets of the stimulus. What are the mechanisms and strategies that guide this selection process? We investigated the influence of various stimulus features on human overt attention--that is, attention related to shifts of gaze with natural color images and modified versions thereof. Our experimental modifications, systematic changes of hue across the entire image, influenced only the global appearance of the stimuli, leaving the local features under investigation unaffected. We demonstrated that these modifications consistently reduce the subjective interpretation of a stimulus as "natural" across observers. By analyzing fixations, we found that first-order features, such as luminance contrast, saturation, and color contrast along either of the cardinal axes, correlated to overt attention in the modified images. In contrast, no such correlation was found in unmodified outdoor images. Second-order luminance contrast ("texture contrast") correlated to overt attention in all conditions. However, although none of the second-order color contrasts were correlated to overt attention in unmodified images, one of the second-order color contrasts did exhibit a significant correlation in the modified images. These findings imply, on the one hand, that higher-order bottom-up effects--namely, those of second-order luminance contrast--may partially account for human overt attention. On the other hand, these results also demonstrate that global image properties, which correlate to the subjective impression of a scene being "natural," affect the guidance of human overt attention.     

Subliminal anchoring: Judgmental consequences and underlying mechanisms

Judgmental anchoring—the assimilation of a numeric estimate towards a previously considered standard—is an exceptionally ubiquitous effect that influences human judgment in a variety of domains and paradigms. Three studies examined whether anchoring effects even occur, if anchor values are presented subliminally, outside of judges’ awareness. Studies 1 and 2 demonstrate such subliminal anchoring effects: judges assimilated target estimates towards the subliminally presented anchor values. Study 3 further demonstrates that subliminal anchors produced a selective increase in the accessibility of anchor-consistent target knowledge. The implications of these findings for the ubiquity of judgmental anchoring, its different underlying mechanisms, and comparative information processing are discussed.     

The long and short of it: physical anchoring effects

Attempts to reconstruct the magnitude of recently encountered physical stimuli were influenced by the provision of physical anchors. Whether estimating length, weight, or loudness, those increasing the magnitude of a relatively small (short, light, or quiet) physical anchor produced estimates that were reliably lower than did those decreasing the magnitude of a relatively large (long, heavy, or loud) anchor. Estimates produced without an anchor were also low, suggesting that when people physically adjust upwards from a self‐selected starting point, “no anchor” may, in fact, act as a very low anchor. Physical anchors appear to influence estimates of recently encountered physical stimuli, much as numerical anchors influence estimates of more abstract numerical quantities. Implications for processes underlying anchoring, adjustment, and related tasks are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Perceived area and the luminosity threshold.

Observers made forced-choice opaque/luminous responses to targets of varying luminance and varying size presented (1) on the wall of a laboratory, (2) as a disk within an annulus, and (3) embedded within a Mondrian array presented within a vision tunnel. Lightness matches were also made for nearby opaque surfaces. The results show that the threshold luminance value at which a target begins to appear self-luminous increases with its size, defined as perceived size, not retinal size. More generally, the larger the target, the more an increase in its luminance induces grayness/blackness into the surround and the less it induces luminosity into the target, and vice versa. Corresponding to this luminosity/grayness tradeoff, there appears to be an invariant: Across a wide variety of conditions, a target begins to appear luminous when its luminance is about 1.7 times that of a surface that would appear white in the same illumination. These results show that the luminosity threshold behaves like a surface lightness value--the maximum lightness value, in fact--and is subject to the same laws of anchoring (such as the area rule proposed by Li & Gilchrist, 1999) as surface lightness.     

Perceived area and the luminosity threshold

Observers made forced-choice opaque/luminous responses to targets of varying luminance and varying size presented (1) on the wall of a laboratory, (2) as a disk within an annulus, and (3) embedded within a Mondrian array presented within a vision tunnel. Lightness matches were also made for nearby opaque surfaces. The results show that the threshold luminance value at which a target begins to appear self-luminous increases with its size, defined as perceived size, not retinal size. More generally, the larger the target, the more an increase in its luminance induces grayness/blackness into the surround and the less it induces luminosity into the target, and vice versa. Corresponding to this luminosity/grayness tradeoff, there appears to be an invariant: Across a wide variety of conditions, a target begins to appear luminous when its luminance is about 1.7 times that of a surface that would appear white in the same illumination. These results show that the luminosity threshold behaves like a surface lightness value—the maximum lightness value, in fact—and is subject to the same laws of anchoring (such as the area rule proposed by Li & Gilchrist, 1999) as surface lightness.     

Elaboration and consequences of anchored estimates: An attitudinal perspective on numerical anchoring

In the standard numerical anchoring paradigm, the influence of externally provided anchors on judgment is typically explained as a result of elaborate thinking (i.e., confirmatory hypothesis testing that selectively activates anchor-consistent information in memory). In contrast, theories of attitude change suggest that the same judgments can result from relatively thoughtful or non-thoughtful processes, with more thoughtful processes resulting in judgments that last longer over time and better resist future attempts at change. Guided by an attitudinal approach to anchoring, four studies manipulated participants’ level of cognitive load to produce relatively high versus low levels of thinking. These studies show that, although anchoring can occur under both high and low thought conditions, anchoring based on a higher level of thinking involves greater use of judgment-relevant background knowledge, persists longer over time, is more resistant to subsequent attempts at social influence, and is less likely to result from direct numeric priming.     

Multiple anchoring of category rating scales

A psychophysical experiment compared the effects of two different kinds of anchoring upon category ratings of the sizes of squares: (1) single anchoring in which the same square was presented on every anchoring trial, and (2) multiple anchoring in which squares of different sizes were presented on anchoring trials. Subjects did not rate the anchors, only those squares presented on alternate trials as the series stimuli. The major finding was that the two kinds of anchoring have similar effects. As with the single anchor, the multiple anchor establishes a new endpoint for the scale of judgment. The previously demonstrated relationship of increasing and then decreasing contrast as a function of the remoteness of the single anchor (Sarris, 1967, 1976) was found also for multiple anchoring.     

When knowledge matters—differential effects of available knowledge in standard and basic anchoring tasks

The present research examines whether anchoring effects—the assimilation of a numeric estimate towards a previously considered standard—depend on judges' available knowledge in the target domain. Based on previous research, I distinguish two types of anchoring effects. Standard anchoring is obtained if judges are explicitly asked to compare the anchor to the target. Basic anchoring results if the accessibility of the anchor is increased prior to judgments about the target. I expected that only basic but not standard anchoring is reduced by providing judges with judgment‐relevant knowledge. Using a standard versus basic anchoring paradigm, 112 participants were confronted with a high versus low anchor before estimating the average price of a German midsize car. Prior to this task, participants were provided with information about prices of cars (relevant knowledge) versus kitchens (irrelevant knowledge). Results demonstrate that this knowledge only influenced the magnitude of basic but not standard anchoring effects. This finding demonstrates that knowledge has differential effects in different types of anchoring. Copyright © 2007 John Wiley & Sons, Ltd.     

Differential consequences of trait inferences: a direct test of the trait-referent hypothesis

The hypothesis was investigated that when trait inferences refer to abstract behaviour labels (i.e. ‘conceited’) they act as a general interpretation frame and lead to assimilation in subsequent judgments of an ambiguous target, whereas when they refer to specific actor—trait links (i.e. ‘Peter is conceited’) the activated information is likely to be used as a scale anchor and contrast effects are more likely. Compared to previous studies investigating the consequences of trait inferences, this ‘trait-referent’ hypothesis was tested in a relatively direct way. Target judgments of participants instructed that trait-implying sentences described a ‘behaviour’ showed assimilation, whereas judgments of participants instructed that these sentences described a ‘person’ showed contrast.     

锚定效应的产生前提及作用机制

为了探讨锚定效应的产生前提以及基础锚定效应的理论解释,设计了两个实验。实验一选取高、低、无三种锚值,设置了15ms、45ms、75ms、1000ms四种呈现时间,结果发现只有15ms条件下未出现锚定效应,随着呈现时间增加,锚定效应不断增大,低锚下的锚定效应高于高锚下的锚定效应。实验二设置了语意相同但表述形式不同的两种水平的锚值,结果发现两者引发的锚定效应不同。锚定效应的产生前提是注意,数字启动假说可以更好地解释基础锚定效应。     

On the determinants of surface brightness

The brightness of an achromatic surface with luminance S on an achromatic background with luminance B varies with S, with B, and with the luminance step deltaL at the border of the surface. In agreement with previous findings indicating that the visual system can perform as a photometer, the results of the two experiments reported here show that S and B determined surface brightness independently of deltaL when the surface was adjacent to and when it was separated from the background. This finding suggests that surface brightness depends on the integration of neural signals representing magnitudes of absolute luminance. A weighted-average model of this integration is proposed.