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PubMed2004

Signal-detection analyses of conditional discrimination and delayed matching-to-sample performance.

Quantitative analyses of stimulus control and reinforcer control in conditional discriminations and delayed matching-to-sample procedures often encounter a problem; it is not clear how to analyze data when subjects have not made errors. The present article examines two common methods for overcoming this problem. Monte Carlo simulations of performance demonstrated that both methods introduced systematic deviations into the results, and that there were genuine risks of drawing misleading conclusions concerning behavioral models of signal detection and animal short-term memory.

Animals↗

PubMed1999

Remember-know judgments can depend on how memory is tested.

Remember-know judgments reflect the subjective state of awareness that accompanies episodic memory retrieval. We tested an old-new recognition condition, an old-new recognition followed by remember-know judgment condition, and a simultaneous remember-know-new judgment condition. These three conditions were tested for both a short (1-sec) and a long (4.5-sec) study duration. Reassuringly, results from the first two conditions did not differ from each other. Results from the third condition, however, differed from those in the first two conditions at both long and short study durations. Simultaneous consideration of all three alternatives resulted in a markedly liberal response bias, both in recognition detection and in the ascriptions of remember and know judgments. Discussion of the results is framed in terms of the single-process signal detection models that have been proposed to account for these subjective states of awareness.

Humans↗

PubMed2005

On measuring the minimum detection time: a simple reaction time study in the time estimation paradigm.

Kornblum's time estimation paradigm, together with the so-called 'race model', provides an appealing alternative for measuring the 'cut-off' which separates 'true' reaction times from anticipatory reaction times. However, the model is not precise enough to reveal the relation between the signal intensity and the 'cut-off'. Accordingly, Kornblum's model is extended with an emphasis on the measure of the 'cut-off'. Another aspect of the extension is to use a parametric method to analyse the data. In particular, it is assumed that the time estimation-induced latency is gamma distributed and the signal-induced latency is Weibull distributed, with the latter shifted by the 'cut-off'. The rationale behind the parametric assumption is discussed. For illustrative purposes, two pieces of experimental work are presented. Since the core of the race model is the assumption of an independent race between the time estimation process and the detection process, the first experiment tests whether, for the same signal intensity, the signal-induced latency distribution is invariant across different time intervals; the second experiment tests whether, for the same time interval, the time estimation-induced latency distribution is invariant across different signal intensity conditions. The data from the second experiment are also used to test various parametric assumptions in the model, which include the signal effect on the 'cut-off'. The new model fits the data well.

Humans↗

PubMed2000

Repetition priming reveals sustained facilitation and transient inhibition in reaction time.

Reaction time (RT) in a detection or a location discrimination task increases when a target is repeatedly presented at the same location (inhibition), whereas RT decreases in feature (color or orientation) discrimination tasks (facilitation; Y. Tanaka & S. Shimojo, 1996a). Here, the time course of inhibition and facilitation was examined, using a repetition priming paradigm. Results indicate that inhibition occurred only in the immediately successive trial, whereas facilitation accumulated over several trials with location repetition. Moreover, inhibition and facilitation occurred in a task-relevant manner: Detection-location discrimination tasks produced transient RT increase, whereas feature discrimination tasks produced cumulative RT decrease. These results suggest a functional dissociation between spatial orienting and feature analysis, as well as top-down modulations by tasks leading to different types of visual memory.

Adult↗

PubMed2001

On the strategic modulation of the time course of facilitation and inhibition of return.

In studies of exogenous attentional orienting, response times for targets at previously cued locations are often longer than those for targets at previously uncued locations. This effect is known widely as inhibition of return (IOR). There has been debate as to whether IOR can be observed in discrimination as well as detection tasks. The experiments reported here confirm that IOR can be observed when target discrimination is required and that the cue-target interval at which IOR is observed is often longer in discrimination than in detection tasks. The results also demonstrate that the later emergence of IOR is related to perceptual discrimination rather than to response selection differences between discrimination and detection tasks. More difficult discrimination tasks lengthen the SOA at which IOR emerges. In contrast, increasing task difficulty by adding a distractor to the location opposite the target shortens the SOA at which IOR emerges. Together, the results reveal an adaptive interaction between exogenous and endogenous attentional systems, in which the action of the orienting (exogenous) system is modulated endogenously in accord with task demands.

Attention↗

PubMed2005

Unconscious inhibition and facilitation at the objective detection threshold: replicable and qualitatively different unconscious perceptual effects.

Although the veridicality of unconscious perception is increasingly accepted, core issues remain unresolved [Jack, A., & Shallice, T. (2001). Introspective physicalism as an approach to the science of consciousness. Cognition, 79, 161-196], and sharp disagreement persists regarding fundamental methodological and theoretical issues. The most critical problem is simple but tenacious-namely, how to definitively rule out weak conscious perception as an alternative explanation for putatively unconscious effects. Using a direct task and objectively undetectable stimuli, the current experiments demonstrate clearly reliable unconscious perceptual effects, which differ qualitatively from weakly conscious effects in fundamental ways. Most importantly, the current effects correlate negatively with stimulus detectability, directly rebutting the exhaustiveness, null sensitivity, and exclusiveness problems [Reingold, E., & Merikle, P. (1988). Using direct and indirect measures to study perception without awareness. Perception & Psychophysics, 44, 563-575; Reingold, E., & Merikle, P. (1990). On the inter-relatedness of theory and measurement in the study of unconscious processes. Mind and Language, 5, 9-28)], which all predict positive correlations. Moreover, the current effects are entirely bidirectional [Katz, (2001). Bidirectional experimental effects. Psychological Methods, 6, 270-281)] and radically uncontrollable, including below-chance performance despite intentions to facilitate. In contrast, weakly conscious effects on direct measures are unidirectional, facilitative, and potentially controllable. Moreover, these qualitative differences also suggest that objective and subjective threshold phenomena are fundamentally distinct, rather than the former simply being a weaker version of the latter [Merikle, P., Smilek, D., Eastwood, J. (2001). Perception without awareness: Perspectives from cognitive psychology. Cognition, 79, 115-134]. Accordingly, it is important to distinguish between rather than conflate these methods. Further, the current effects reinforce recent work [e.g. Naccache, L., Blandin, E., & Dehaene, S. (2002). Unconscious masked priming depends on temporal attention. Psychological Science, 13, 416-424] demonstrating that unconscious effects, although not selectively controllable, are nonetheless mediated by strategic and individual difference factors, rather than being immune to such influences as long thought.

Adult↗

PubMed2004

A psychophysical test of the vibration theory of olfaction.

At present, no satisfactory theory exists to explain how a given molecule results in the perception of a particular smell. One theory is that olfactory sensory neurons detect intramolecular vibrations of the odorous molecule. We used psychophysical methods in humans to test this vibration theory of olfaction and found no evidence to support it.

Adult↗

PubMed2005

Recognition bias for critical faces in social phobia: a replication and extension.

Studies using linguistic stimuli have provided little support for explicit memory biases among individuals with social phobia (SP). However, using facial stimuli rated on their criticalness, Lundh and Ost (1996) found that individuals with SP recognized more critical than accepting faces, whereas non-anxious controls tended to show the opposite pattern. Since the publication of Lundh and Ost's findings, additional studies using a variety of facial stimuli have produced inconsistent findings (J. Anxiety Disord. 14 (2000) 501; Behav. Res. Ther. 39 (2001) 967). Unfortunately, these inconsistencies are difficult to reconcile given great variation in methods and stimuli. Therefore, we designed a study to replicate and extend the work of Lundh and Ost (Behav. Res. Ther. 34 (1996) 787). Similar to Lundh and Ost, individuals with SP identified a significantly higher proportion of old critical faces as old than did non-anxious controls. Further, extending the work of Lundh and Ost, signal detection analyses revealed group differences on response bias according to face type. Specifically, controls showed a response bias towards indicating that accepting faces were previously seen, whereas individuals with SP did not. Finally, signal detection analyses failed to reveal group differences in the accuracy of memory.

Adolescent↗

PubMed2006

Age of acquisition affects object recognition: evidence from visual duration thresholds.

The impact of age of acquisition (AoA) on object recognition was explored in three experiments measuring visual duration threshold (VDT) for the identification of pictures labelled with early and late acquired names. Participants viewed briefly displayed images preceded and followed by a pattern mask. The minimum display duration required for correct identification was shorter for pictures labelled with early names than for those labelled with late names. In Experiments 2 and 3 we explored the effects of two forms of visual degradation on VDT for pictures with early and late acquired names. Both degradation by superimposed visual elements, and degradation by contrast reduction extended VDT, but only the former interacted with AoA. We conclude that both AoA and degradation by superimposed visual elements affect the efficiency of visual object recognition, but only degradation by contrast and not AoA affects the efficiency of earlier pre-recognition processes.

Analysis of Variance↗

PubMed2005

Individuation of visual objects over time.

How does an observer decide that a particular object viewed at one time is actually the same object as one viewed at a different time? We explored this question using an experimental task in which an observer views two objects as they simultaneously approach an occluder, disappear behind the occluder, and re-emerge from behind the occluder, having switched paths. In this situation the observer either sees both objects continue straight behind the occluder (called "streaming") or sees them collide with each other and switch directions ("bouncing"). This task has been studied in the literature on motion perception, where interest has centered on manipulating spatiotemporal aspects of the motion paths (e.g. velocity, acceleration). Here we instead focus on featural properties (size, luminance, and shape) of the objects. We studied the way degrees and types of featural dissimilarity between the two objects influence the percept of bouncing vs. streaming. When there is no featural difference, the preference for straight motion paths dominates, and streaming is usually seen. But when featural differences increase, the preponderance of bounce responses increases. That is, subjects prefer the motion trajectory in which each continuously existing individual object trajectory contains minimal featural change. Under this model, the data reveal in detail exactly what magnitudes of each type of featural change subjects implicitly regard as reasonably consistent with a continuously existing object. This suggests a simple mathematical definition of "individual object:" an object is a path through feature-trajectory space that minimizes feature change, or, more succinctly, an object is a geodesic in Mahalanobis feature space.

Bayes Theorem↗

PubMed2004

Spatial attention speeds discrimination without awareness in blindsight.

An intimate relationship is often assumed between visual attention and visual awareness. Using a subject, patient GY, with the neurological condition of "blindsight" we show that although attention may be a necessary precursor to visual awareness it is not a sufficient one. Using a Posner endogenous spatial cueing paradigm we showed that the time our subject needed to discriminate the orientation of a stimulus was reduced if he was cued to the location of the stimulus. This reaction-time advantage was obtained without any decrease in discrimination accuracy and cannot therefore be attributed to speed-error trade-off or differences in bias between cued and uncued locations. As a result of his condition GY was not aware of the stimuli to which processing was attentionally facilitated. Attention cannot, therefore be a sufficient condition for awareness.

Adult↗

PubMed1999

Mechanisms of perceptual learning.

Systematic measurements of perceptual learning were performed in the presence of external or stimulus noise. In the new external noise method (Dosher, B, & Lu, Z.-L. (1997). Investigative Ophthalmology and Visual Science, 38, S687; Lu, Z.-L., & Dosher, B. (1998). Vision Research, 38, 1183-1198), increasing amounts of external noise (white Gaussian random noise) is added to the visual stimulus in order to identify mechanisms of perceptual learning. Performance improved (threshold contrast was reduced) over days of practice on a peripheral orientation discrimination task--labelling Gabor patches as tilted slightly to the right or left. Practice improvements were largely specific to the trained quadrant of the display. Performance improved at all levels of external noise. The external noise method and perceptual template model (PTM) of the observer identifies the mechanism(s) of performance improvements as due to stimulus enhancement, external noise exclusion, or internal noise suppression. The external noise method was further extended by measuring thresholds at two threshold performance levels, allowing identification of mixtures in the PTM model. Perceptual learning over 8-10 days improved the filtering or exclusion of external noise by a factor of two or more, and improved suppression of additive internal noise--equivalent to stimulus enhancement--by 50% or more. Coupled improvements in external noise exclusion and stimulus enhancement in the PTM model may reflect channel weighting. Perceptual learning may not reflect neural plasticity at the level of basic visual channels, nor cognitive adjustments of strategy, but rather plasticity at an intermediate level of weighting inputs to decision.

Discrimination, Psychological↗

PubMed1999

A simple saliency model predicts a number of motion popout phenomena.

Visual search for a moving target among stationary distractors is more efficient than searching for a stationary target among moving distractors, and searching for a fast target among slow distractors is more efficient than vice versa. This indicates that the ease of search for a target with a particular motion is not determined simply by the difference between target and distractor velocities. We suggest a simple model for predicting ease of search for a unique motion, based upon a quantitative measure of target saliency. Essentially, search will be easier the more the target motion deviates from the general pattern of velocities in the scene. Our model predicts a number of well-known motion search phenomena, and suggests that one control for target saliency as well as target discriminability when drawing conclusions about visual system mechanisms from search experiments.

Color Perception↗

PubMed2000

Asymmetries in a unilateral flanker task depend on the direction of the response: the role of attentional shift and perceptual grouping.

Four experiments were conducted using a flanker task with 1 distractor appearing either on the left or right side of a central target. Responses were made on a keyboard aligned parallel to the displays. A larger flanker effect was obtained when the distractor was on the same side as the response. Two factors account for this asymmetry. First, when the flanker and target are identical, the 2 form a group that is assigned a spatial tag, creating a form of the Simon effect on the basis of the compatibility between the response keys and the group. Second, preparation of a lateralized response appears to entail a shift of visual attention in the corresponding direction, thus enhancing processing of the flanker on the response side. Consistent with the 2nd hypothesis, participants were more likely to correctly recognize letters that were briefly presented at the distractor position on the same side as the response.

Adult↗

PubMed1995

Process dissociation, single-process theories, and recognition memory.

According to the assumptions of L. L. Jacoby's (1991) process dissociation method, performance in recognition memory is determined by the combination of an unconscious familiarity process and a conscious intentional recollection process. The process dissociation method is used to produce estimates of the contributions of the 2 components to recognition performance. This article investigates whether the method provides the correct estimates of components if performance actually depends on only a single process or on 2 processes different from those assumed by the method. The SAM model (G. Gillund & R. M. Shiffrin, 1984) was used to produce simulated data based on a single process. Variants of SAM with 2 processes and R. C. Atkinson and J. F. Juola's (1973) 2-process model were used to produce data based on 2 processes.

Cognition↗

PubMed1998

On the difference between strength-based and frequency-based mirror effects in recognition memory.

A mirror effect can be produced by manipulating word class (e.g., high vs. low frequency) or by manipulating strength (e.g., short vs. long study time). The results of 5 experiments reported here suggest that a strength-based mirror effect is caused by a shift in the location of the decision criterion, whereas a frequency-based mirror effect occurs although the criterion remains fixed with respect to word frequency. Evidence supporting these claims is provided by a series of studies in which high frequency (HF) words were differentially strengthened (and sometimes differentially colored) during list presentation. That manipulation increased the HF hit rate above that for low frequency (LF) words without selectively decreasing the HF false alarm rate, just as a fixed-criterion account of the word-frequency mirror effect predicts.

Adult↗

PubMed1999

Inhibition in the processing of garden-path sentences.

The Hartman and Hasher (1991) garden-path sentence completion task has been used in several studies to assess the efficiency of the deletion function of inhibition (e.g., L. Hasher, R. Zacks, & C. P. May, 1999 ), with results suggesting that younger adults are efficient at suppressing once relevant but no longer appropriate information, whereas older adults generally are not (e.g., M. Hartman & L. Hasher, 1991: L. Hasher. M. B. Quig, & C. P. May, 1997; C. P. May & L. Hasher, 1998). An alternative interpretation of patterns of access to relevant and no-longer-relevant sentence endings focuses on the difficulty of selecting final words for sentence frames and on integration effects in implicit memory (M. Hartman, 1995). This alternative is considered and found wanting on the basis of both new and old empirical data. On the basis of present data and related findings, it is concluded that the task does measure inhibitory efficiency.

Adolescent↗

PubMed2001

Perception and preference in short-term word priming.

Responding optimally with unknown sources of evidence (ROUSE) is a theory of short-term priming applied to associative, orthographic-phonemic, and repetition priming. In our studies, perceptual identification is measured with two-alternative forced-choice testing. ROUSE assumes features activated by primes are confused with those activated by the target. A near-optimal decision discounts evidence arising from such shared features. Too little discounting explains the finding that primed words were preferred after passive viewing of primes. Too much discounting explains the findings of reverse preference after active processing of primes. These preference changes highlight the need to use paradigms (like the present ones) capable of separating preferential and perceptual components of priming. Evidence of enhanced perception was found only with associative priming and was very small in magnitude compared with preference effects.

Analysis of Variance↗