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PubMed1999

Estimator reliability and distance scaling in stereoscopic slant perception.

When a horizontal or vertical magnifier is placed before one eye, a frontoparallel surface appears slanted. It appears slanted away from the eye with horizontal magnification (geometric effect) and toward the eye with vertical magnification (induced effect). According to current theory, the apparent slant in the geometric and induced effects should increase with viewing distance. The geometric effect does scale with distance, but there are conflicting reports as to whether the induced effect does. Ogle (1938 Archives of Ophthalmology 20 604-623) reported that settings in slant-nulling tasks increase systematically with viewing distance, but Gillam et al (1988 Perception & Psychophysics 44 473-483) and Rogers et al (1995 Perception 24 Supplement, 33) reported that settings in slant-estimation tasks do not. We re-examined this apparent contradiction. First, we conducted two experiments whose results are consistent with the literature and thus replicate the apparent contradiction. Next, we analyzed the signals available for stereoscopic slant perception and developed a general model of perceived slant. The model is based on the assumption that the visual system knows the reliability of various slant-estimation methods for the viewing situation under consideration. The model's behavior explains the contradiction in the literature. The model also predicts that, by manipulating eye position, apparent slant can be made to increase with distance for vertical, but not for horizontal, magnification. This prediction was confirmed experimentally.

Adult↗
PubMed1999

Examining the effect of practice on inhibition of return in static displays.

In a recent article, Weaver, Lupiáñez, and Watson (1998) reported that both object-based and location-based inhibition of return effects were reduced with practice. The present study was conducted to (1) replicate the reduction of inhibition of return with practice in single-session experiments with a variety of displays and responses and (2) to examine the notion that the reduction was, at least partly, due to habituation. However, no evidence for practice-related changes in the size of the inhibitory effect were found over a series of different inhibition of return experiments using static displays (using various numbers of target locations, types of keypress responses, and number of trials). Overall, the results suggest that inhibition of return is a robust phenomenon and may not, with static displays, be especially sensitive to practice effects.

Adult↗
PubMed1998

"Transient structures": the effects of practice and distractor grouping on within-dimension conjunction searches.

It has been stated that whereas between-dimension (color x orientation) conjunctions can be searched in a "parallel" fashion, within-dimension (color x color) conjunctions are necessarily searched in a "serial self-terminating" fashion (Wolfe et al., 1990). We explored the effects of practice (within 1-h experimental session) and distractor grouping on within-dimension conjunction search tasks. In Experiments 1 and 3, the stimuli were rectangles formed by two adjacent squares; in Experiment 2, the stimuli were plus signs formed by two segments and an intersection. In Experiments 1 and 2, observers were assigned to one of two experimental conditions: In one, all the distractors shared a simple feature (the color blue); in the other, distractors did not share that simple feature. In the first condition, search became more efficient with practice and observers' performance was characterized by a shallow reaction time (RT) x set size slope; in the second condition, observers' performance did not improve as much with practice. We propose that the differential effects of practice between these two experimental conditions can be explained in terms of distractor grouping induced by the shared color of the distractors. Experiment 3 showed that, with practice, a shallow RT x set size slope characterized observers' search for a color x color target among four different distractors that shared a common color. The present results contradict a main tenet of some current visual search models--namely, that within-dimension conjunctions cannot be searched in parallel, and question the validity of using RT x set size slope functions to distinguish between preattentive versus attentive search.

Analysis of Variance↗
PubMed1994

Categorization response time with multidimensional stimuli.

Categorization response time (RT) was examined in three separate experiments, in each of which exemplars varied on two physical dimensions. Three different types of stimuli were used: (1) horizontal and vertical line segments of varying length that were joined at an upper left corner, (2) rectangles of varying width and height, and (3) circles or semicircles of varying size with a radial arm of varying orientation. No evidence was found that stimulus familiarity or the category prototypes played any special role in determining categorization RT. Instead, RT decreased with distance from the stimulus to the categorization decision bound.

Decision Making↗
PubMed2000

Tracking visual search over space and time.

Visual perception consists of early preattentive processing and subsequent attention-demanding processing. Most researchers implicitly treat preattentive processing as a domain-dependent, indivisible stage. We show, however, by interrupting preattentive visual processing of color before its completion, that it can be dissected both temporally and spatially. The experiment depends on changing easy (preattentive) selection into difficult (attention-demanding) selection. We show that although the mechanism subserving preattentive selection completes processing as early as 200 msec after stimulus onset, partial selection information is available well before completion. Furthermore, partial selection occurs first at locations near fixation, spreading radially outward as processing proceeds.

Adult↗
PubMed1999

Neurophysiologic mechanisms of attention deficits in schizophrenia.

BACKGROUND: Despite advances in the pharmacologic treatment of schizophrenia, the neurophysiologic mechanism(s) of disordered attention in schizophrenia remain elusive. OBJECTIVE: The goal of the present study was to assess specific components of attention, including disengagement, movement, re-engagement, and the inhibitory processes involved their control. METHODS: Thirteen chronic schizophrenics from the inpatient and outpatient units of the Veterans Administration Medical Center (New Orleans, LA) and thirteen normal control subjects were administered a saccadic eye movements task. Saccade latency was measured in the presence of contra-lateral distracter stimuli that preceded the target onset (Distracter-before), followed the target onset (Distracter - after) or in the absence of a distracter (No-distracter). In order to assess the interactive process of fixation disengagement and target selection, fixation was either offset before the target (Gap) or it remained on in the presence of the target (Overlap). RESULTS: Repeated measures analysis of variance revealed that saccadic latency in patients with schizophrenia is prolonged to a greater extent than in normal control subjects in the presence of distracter stimuli. Patients with schizophrenia are also characterized by a greater percentage of error saccades directed to the distracter, and require a longer latency to "issue" corrective saccades following error saccades. CONCLUSIONS: The findings suggest that patients with schizophrenia are required to invoke volitional control under distracter conditions, whereas normal control subjects require minimal volitional control. The results are interpreted in terms of the inhibitory mechanisms that regulate attention.

Adult↗
PubMed1999

[Hemisphere asymmetry in repetitive priming and associative priming].

This study investigated hemispheric asymmetries in repetition priming (Experiment 1) and associative priming (Experiment 2) in visual word recognition. Participants performed speeded lexical decisions for foveally presented target words that could be preceded by prime words presented to the left (LVF) or right (RVF) visual field. Experiment 1 demonstrated larger repetition priming in reaction times when prime words were presented to the RVF (left hemisphere). In contrast, no repetition priming was observed for pseudowords. Hemispheric asymmetries in word repetition priming may therefore reflect the superiority of the left hemisphere in activating lexical representations. Experiment 2 did not find any hemispheric asymmetries in associative priming. The results suggest that repetition priming and associative priming act on different levels in word recognition, for which different hemispheric asymmetries exist.

Adult↗
PubMed2007

Dual-process theory and signal-detection theory of recognition memory.

Two influential models of recognition memory, the unequal-variance signal-detection model and a dual-process threshold/detection model, accurately describe the receiver operating characteristic, but only the latter model can provide estimates of recollection and familiarity. Such estimates often accord with those provided by the remember-know procedure, and both methods are now widely used in the neuroscience literature to identify the brain correlates of recollection and familiarity. However, in recent years, a substantial literature has accumulated directly contrasting the signal-detection model against the threshold/detection model, and that literature is almost unanimous in its endorsement of signal-detection theory. A dual-process version of signal-detection theory implies that individual recognition decisions are not process pure, and it suggests new ways to investigate the brain correlates of recognition memory.

Humans↗
PubMed2001

Hyperefficient detection of targets in noisy images.

We compared human detection of visual targets in noisy images with that of a theoretically optimum matched filter. Using a small thin target with vertically aligned markers, we obtained hyperefficient detection as high as 91% as compared with the theoretical optimum, a value far exceeding the 30-50% value typically reported. When the markers were removed, detection efficiencies degraded to an average of 27%, even though subjects were aware that the target was always placed in the center of a reasonably small panel. Using a nine-alternative forced-choice experiment, we compared detection by human observers with a matched-filter computational observer on a trial-by-trial basis. With the markers present, when humans missed the correct panel, they most often chose the panel with the second-highest decision variable output from the computational observer, suggesting that the template-matching model is a good one. To model results without the markers, we included location uncertainty and additional noise sources in the template matching of the computational observer. A location uncertainty of only 1 pixel, corresponding to a retinal distance of approximately 12 microm, a dimension of the order of the size of the receptive field of photoreceptors, explained the psychometric data. With the marker present, the model suggests that hyperefficient detection is obtained by limiting target location uncertainty to <6 microm. Together these results give important new insights into human visual detection mechanisms.

Artifacts↗
PubMed2002

Effects of questions' repetition and variation on the efficiency of the guilty knowledge test: a reexamination.

The effect of question repetition and variation on the efficiency of the Guilty Knowledge Test (GKT), based on electrodermal and respiration measures, was examined in a between-subjects experiment with 3 conditions. Each participant was presented with a sequence of 12 biographical questions. In Condition 1, a single question was repeated 12 times; in Condition 4, each of 4 different questions was repeated 3 times; and in Condition 12, 12 different questions were used. A monotonic relationship between the number of different questions used and detection efficiency was observed only with the electrodermal measure (the areas under the receiver operating characteristic curves, obtained with this measure in Conditions 1, 4, and 12 were .68, .81, and .99, respectively). These results demonstrate that a GKT based on multiple questions is superior to the use of many repetitions of a single or a few questions, and it can reach an almost perfect detection efficiency.

Adult↗
PubMed2000

Predicting individual false alarm rates and signal detection theory: a role for remembering.

The relationships between hit, remember, and false alarm rates were examined across individual subjects in three remember-know experiments in order to determine whether signal detection theory would be consistent with the observed data. The experimental data differed from signal detection predictions in two critical ways. First, remember reports were unrelated, or slightly negatively related, to the commission of false alarms. Second, both response types (remembers and false alarms) were uniquely related to hit rates, which demonstrated that the hit rate cannot be viewed as the result of a single underlying strength process. These results are consistent with the dual-process signal detection model of Yonelinas (1994), in which performance is determined by two independent processes--retrieval of categorical context information (remembering) and discriminations based on continuous item strength. Remember and false alarm rates selectively tap these processes, whereas the hit rate is jointly determined. Monte Carlo simulations in which the dual-process model was used successfully reproduced the pattern in the experimental data, whereas simulations in which a signal detection model, with separate "old" and "remember" criteria, was used, did not. The results demonstrate the utility of examining individual differences in response types when one is evaluating memory models.

Adult↗
PubMed1999

A generalized signal detection model to predict rational variation in base rate use.

The predominant models of rational behavior currently used to analyze a large class of experiments imply that subjects neglect or place insufficient weight on base rates when making probabilistic judgments. We argue that the evidence is inadequate for this conclusion because the models make needlessly restrictive assumptions about how base rates should be used. The restrictive assumptions stem from a misuse of Bayes' rule that ignores specific aspects of how the proportions arose. We develop a model of rational behavior that generalizes signal detection theory to reflect the environment subjects routinely face and we reexamine the relevant experimental literature. Variation observed in subjects' responses to base rate information is explained by the present rational model more fully than by extant models.

Adult↗
PubMed2006

Asymmetries in categorization, perceptual discrimination, and visual search for reference and nonreference exemplars.

In two experiments, we examined the representation, treatment, and attention devoted to the members of reference (i.e., club members) and nonreference (i.e., not club members) categories. Consistent with prior work on category interrelatedness (e.g., Goldstone, 1996; Goldstone, Steyvers, and Rogosky, 2003), the findings reveal the existence of asymmetric representations for reference and nonreference categories, which, however, decreased as expertise and familiarity with the categories increased (Experiments 1 and 2). Participants also more readily judged two reference exemplars as being the same than they did two nonreference exemplars (Experiment 1) and were better at detecting reference than nonreference exemplars in a set of novel, category-unspecified exemplars (Experiment 2). These findings provide evidence for the existence of a feature asymmetry in the representation and treatment of exemplars from reference and nonreference categories. Membership in a reference category acts as a salient feature, thereby increasing the perceived similarity and detection of faces that belong in the reference, in comparison with the nonreference, category.

Discrimination, Psychological↗
PubMed2005

Word-imagery effects on recollection and familiarity in recognition memory.

The Remember/Know procedure was used to investigate the effects of word imageability on recognition memory. An experiment, using French-speaking undergraduate students (17 women and 3 men), replicated Dewhurst and Conway's 1994 finding that rated imageability significantly increased accurate Remember responses but not Know responses when analyzed in the traditional way, assuming that the response types are mutually exclusive. Data were also analyzed using the Yonelinas, et al. 1998 dual-process signal-detection model, for estimating recollection and familiarity while assuming that Remember and Know responses are independent. Analysis indicated significant enhancement of imageability for estimates of both recollection and familiarity. This was interpreted as meaning that imageability enhanced both item-specific and contextual information associated with studied words.

Adolescent↗
PubMed2002

Measuring the search image: expectation, detection, and recognition in pigeon visual search.

Pigeons searched computer screens for a grating target that varied in spatial frequency and orientation. In Experiment 1, a pretrial cue signaled that a particular target would appear. The cue speeded response to this primed target and to targets of the same orientation and similar spatial frequency to the primed target. However, the cue slowed search for targets differing from the primed target in orientation. In Experiment 2, pecks to a single target were reinforced. Responding generalized somewhat to targets of spatial frequency similar to the primed target and to targets of either orientation. Thus, stimulus aspects that affect detection may differ from those that affect recognition; if a common representation serves both, it functions differently in the 2 cases.

Analysis of Variance↗
PubMed2005

ROCs in recognition with and without identification.

Receiver operating characteristics (ROCs) for the recognition of unidentified word fragments were analysed and compared with ROCs for the recognition of identified word fragments. In all conditions reported here, the z-transformed ROCs (z-ROCs) for recognition without identification were linear, with slopes near 1.0. In contrast, the z-ROCs for recognition with identification each had both a linear and a quadratic component, and a slope of substantially less than 1.0. Because the recognition of unidentified word fragments likely results from a familiarity process, the present study examined how well the effect can be explained by global matching variants of signal detection theory. Global matching models predict that memory should be better for strong items from a mixed list than for strong items from a pure list, and should be worse for weak items from a mixed list than for weak items from a pure list; however, only the latter pattern was shown for the recognition of unidentified items.

Cues↗
PubMed2005

Split-brain reveals separate but equal self-recognition in the two cerebral hemispheres.

To assess the ability of the disconnected cerebral hemispheres to recognize images of the self, a split-brain patient (an individual who underwent complete cerebral commissurotomy to relieve intractable epilepsy) was tested using morphed self-face images presented to one visual hemifield (projecting to one hemisphere) at a time while making "self/other" judgments. The performance of the right and left hemispheres of this patient as assessed by a signal detection method was not significantly different, though a measure of bias did reveal hemispheric differences. The right and left hemispheres of this patient independently and equally possessed the ability to self-recognize, but only the right hemisphere could successfully recognize familiar others. This supports a modular concept of self-recognition and other-recognition, separately present in each cerebral hemisphere.

Aged↗