The whole moves less than the spin of its parts

When individually moving elements in the visual scene are perceptually grouped together into a coherently moving object, they can appear to slow down. In the present article, we show that the perceived speed of a particular global-motion percept is not dictated completely by the speed of the local moving elements. We investigated a stimulus that leads to bistable percepts, in which local and global motion may be perceived in an alternating fashion. Four rotating dot pairs, when arranged into a square-like configuration, may be perceived either locally, as independently rotating dot pairs, or globally, as two large squares translating along overlapping circular trajectories. Using a modified version of this stimulus, we found that the perceptually grouped squares appeared to move more slowly than the locally perceived rotating dot pairs, suggesting that perceived motion magnitude is computed following a global analysis of form. Supplemental demos related to this article can be downloaded from app.psychonomic-journals.org/content/supplemental.     

Erratum: Decision anomalies,experimenter assumptions,and participants' comprehension: Revaluating the uncertainty effect

The above article (DOI: 10.1002/bdm.628 ) was published online on 14 November 2008 inWiley InterScience ( www.interscience.wiley.com ). An error was subsequently identified: Page 3, line 22: “certainty effect,” should read “uncertainty effect,”.     

The meaning of indifference in choice behavior: Asymmetries in adjustments embodied in matching

Measuring and assessing people’s preferences is an intricate task that can be realized by different methods. Evidently, the different methods do not necessarily yield consistent results. In the present paper we examine the matching procedure and demonstrate inconsistencies within the method itself. It is shown that the inconsistencies stem from: (1) asymmetry in upward and downward matching (i.e., matching options by increasing or lowering values do not yield the same tradeoffs) and (2) participants’ tendency to match (adjust) the options such that they become more similar, eventually facilitating the choice process. Matching is the most straightforward method of eliciting indifference. Hence, the observed inconsistencies, encapsulated in the matching procedure, have direct implications for the construction of indifference curves (equal-utility contours) that are examined in the final section.     

Negative-based prominence: the role of negative features in matching and choice

Previous research related to the prominence effect (e.g., Tversky, Sattath, & Slovic, 1988) has mainly focused on the causes and boundary conditions of the effect. This article investigates the determinants of prominence and explores a negative-based prominence effect in which the negative attribute becomes the prominent one. Using a matching-choice procedure, Experiments 1 and 2 show that the negative dimension became the prominent one under two different cover stories, suggesting that the negative feature looms larger in choice than in matching. The robustness of negative-based prominence was further demonstrated in a direct choice task without matching (Experiment 3) and was shown to be resistant to the impact of added positive features (Experiment 4). Finally, Experiments 5 and 6 distinguish between two determinants of prominence: intrinsic prominence caused by attribute importance and negative-based prominence caused by negative attribute values. By lowering the values on the positive dimension and enhancing the values on the negative dimension, one can reverse the prominence effect. The results suggest that, compared to a matching task, choice leads to enhanced sensitivity to negative features. The relations between negative characteristics of an attribute and other factors that determine prominence are discussed in the final section.     

Failures to see: attentive blank stares revealed by change blindness

Change blindness illustrates a remarkable limitation in visual processing by demonstrating that substantial changes in a visual scene can go undetected. Because these changes can ultimately be detected using top-down driven search processes, many theories assign a central role to spatial attention in overcoming change blindness. Surprisingly, it has been reported that change blindness can occur during blink-contingent changes even when observers fixate the changing location [O'Regan, J. K., Deubel, H., Clark, J. J., & Rensink, R. A. (2000). Picture changes during blinks: Looking without seeing and seeing without looking. Visual Cognition, 7, 191-212]. However, eye blinks produce a transient disruption of vision that is independent of any associated changes in the retinal image. We determined whether these 'attentive blank stares' could occur in the absence of blink-mediated visual suppression. Using a flicker change-blindness paradigm we confirm that despite direct attentive fixations, obvious scene changes often remain undetected. We conclude that change detection involves object or feature based attentional mechanisms, which can be 'misdirected' despite the allocation of spatial attention to the position of the change.     

Examining interrelationships between the Cigarette Purchase Task and delay discounting among pregnant women

Two common behavioral economic simulation tasks used to study cigarette smoking are the Cigarette Purchase Task, a measure of cigarette demand, and delay discounting, a measure of the subjective value of rewards as a function of delays to delivery. Few studies have evaluated whether combining these tasks enhances understanding of smoking beyond either alone. The current study represents an initial evaluation of the intersection between cigarette demand indices and delay discounting among pregnant smokers by examining associations between these measures and whether a woman makes antepartum quit attempts before entering prenatal care (a reliable predictor of eventual quitting). Participants were 159 pregnant women enrolled in a smoking‐cessation trial. Low O _max and shallow discounting were each associated with antepartum quit attempts. Participants were next categorized into four subgroups (low O _max, shallow discounting; low O _max, steep discounting; high O _max, shallow discounting; high O _max, steep discounting) using median splits. Those with shallow discounting and low O _max were more likely to have made quit attempts than each of the other three subgroups. That is, steep discounting appears to undermine the association of low O _max and efforts to quit smoking during pregnancy while high O _max overshadows any protective influence associated with shallow discounting.     

Hemispheric visual atentional imbalance in patients with traumatic brain injury

We find a spatially asymmetric allocation of attention in patients with traumatic brain injury (TBI) despite the lack of obvious asymmetry in neurological indicators. Identification performance was measured for simple spatial patterns presented briefly to a locus 5 degrees into the left or right hemifield, after precuing attention to the same (ipsilateral) or opposite (cross-hemifield) side. Though the cue was non-predictive of target location overall, performance was significantly slower for cross than for ipsilateral trials in both patients and controls. We tested 21 TBI patients without overt focal brain damage and nine control subjects. Only patients demonstrated significantly worse performance for left side presentation in the ipsilateral condition. Furthermore, in the cross-hemifield condition, the left-right difference seen in TBI patients was significantly larger-reflecting a failure in producing a leftward attention shift. Again no significant difference was found in controls. These hemifield effects suggest an asymmetry in the ability of TBI patients in shifting attention to the left hemifield, whether from central fixation or from a cue in the contra-lateral hemifield. The results support basic hypotheses regarding visual attention: Attentional control may be asymmetric and attention may be a distributed, rather than localized cortical function.     

BOLD activation varies parametrically with corner angle throughout human retinotopic cortex

The Alternating Brightness Star (ABS) is an illusion that provides insight into the relationship between brightness perception and corner angle. Recent psychophysical studies of this illusion have shown that corner salience varies parametrically with corner angle, with sharp angles leading to strong illusory percepts and shallow angles leading to weak percepts. It is hypothesized that the illusory effects arise because of an interaction between surface corners and the shape of visual receptive fields: sharp surface corners may create hotspots of high local contrast due to processing by center-surround and other early receptive fields. If this hypothesis is correct, early visual neurons should respond powerfully to sharp corners and curved portions of surface edges. Indeed, the primary role of early visual neurons may be to localize the discontinuities along the edges of surfaces. If so, all early visual areas should show greater BOLD responses to sharp corners than to shallow corners. On the other hand, if corner processing is exclusively constrained to certain areas of the brain, only those specific areas will show greater responses to sharp vs shallow corners. To address this we explored the BOLD correlates of the ABS illusion in the human visual cortex using fMRI. We found that BOLD signal varies parametrically with corner angle throughout the visual cortex, offering the first neurophysiological correlates of the ABS illusion. This finding provides a neurophysiological basis for the previously reported psychophysical data that showed that corner salience varied parametrically with corner angle. We propose that all early visual areas localize discontinuities along the edges of surfaces, and that specific cortical corner-processing circuits further establish the specific nature of those discontinuities, such as their orientation.     

Segment duration as a cue to word boundaries in spoken-word recognition

In two eye-tracking experiments, we examined the degree to which listeners use acoustic cues to word boundaries. Dutch participants listened to ambiguous sentences in which stop-initial words (e.g., pot, jar) were preceded by eens (once); the sentences could thus also refer to cluster-initial words (e.g., een spot, a spotlight). The participants made fewer fixations to target pictures (e.g., ajar) when the target and the preceding [s] were replaced by a recording of the cluster-initial word than when they were spliced from another token of the target-bearing sentence (Experiment 1). Although acoustic analyses revealed several differences between the two recordings, only [s] duration correlated with the participants' fixations (more target fixations for shorter [s]s). Thus, we found that listeners apparently do not use all available acoustic differences equally. In Experiment 2, the participants made more fixations to target pictures when the [s] was shortened than when it was lengthened. Utterance interpretation can therefore be influenced by individual segment duration alone.