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At least 109 records · Page 6Linked to original sources

PubMed2005

Unconscious perception or not? An evaluation of detection and discrimination as indicators of awareness.

Most investigations of unconscious perception use a dissociation design in which an awareness variable (e.g., detection) is compared with a perceptual processing variable (e.g., identification). Unconscious perception is inferred when the awareness variable lacks sensitivity to the stimulus but evidence of perceptual processing is still obtained. In two studies we examined the relationship between word identification and detection (Study 1) or discrimination (words vs. nonwords; Study 2) with a variety of techniques. In both studies, dissociations suggestive of unconscious perception occurred when the data were examined with subjective threshold approaches, but these differences disappeared when the variables were compared with techniques derived from signal detection theory (SDT). These results do not support unconscious perception in subjective threshold paradigms. In addition, detection appears to be the most sensitive and appropriate task for assessing stimulus awareness, provided that several SDT assumptions are met.

Awareness↗

PubMed1998

A competition model of exogenous orienting in 3.5-month-old infants.

Four experiments are reported on exogenous (stimulus-driven) orienting in 3.5-month-old infants. A small moving bar embedded in a field of static bars was used to draw the infant's attention to one side of the display or the other. The bars could be either red or green. In all four of these experiments sensitivity to this small moving bar was affected significantly by how unevenly the red and green bars were distributed across the visual field. Sensitivity to the moving bar was lower when most of the red bars were in the field contralateral to this probe suggesting competition between the motion stimulus and contralaterally placed red but not green bars on a small, but significant proportion of trials. This basic effect replicated in four separate experiments and depended coarsely on how unevenly the red and the green bars were distributed across the field. A competition model of exogenous orienting with a winner-take-all rule captured the most important features of the data. The distribution of color within the visual field can bias attention significantly at 3.5 months making it either more or less likely that an infant will detect a moving stimulus.

Attention↗

PubMed2002

Do juries meet our expectations?

Surveys of public opinion indicate that people have high expectations for juries. When it comes to serious crimes, most people want errors of convicting the innocent (false positives) or acquitting the guilty (false negatives) to fall well below 10%. Using expected utility theory, Bayes' Theorem, signal detection theory, and empirical evidence from detection studies of medical decision making, eyewitness testimony, and weather forecasting, we argue that the frequency of mistakes probably far exceeds these "tolerable" levels. We are not arguing against the use of juries. Rather, we point out that a closer look at jury decisions reveals a serious gap between what we expect from juries and what probably occurs. When deciding issues of guilt and/or punishing convicted criminals, we as a society should recognize and acknowledge the abundance of error.

Bayes Theorem↗

PubMed2004

Effects of outside issues on the comparison question test.

In the present study, the authors examined the effects of outside issues on the validity of the Comparison Question Test in a laboratory mock-crime paradigm. In a 2 x 2 x 2 factorial design, 192 participants either did or did not commit (a) a mock theft of a dollar (about which they were tested), or (b) a mock theft of dollars 20 (the outside issue); and they either were or were not asked questions about an outside issue. The presence of the outside issue had a strong differential impact on the participants who were innocent of the tested issue, and it dramatically moved their scores toward deception. The impact of an outside issue on the guilty was minimal. Test questions about possible outside issues were ineffective in detecting the presence of the outside issue, but they did function as comparison questions. The results have implications for understanding the high rate of false positive outcomes in some studies.

Adult↗

PubMed2003

Error-proneness as a handicap signal.

This paper describes two discrete signalling models in which the error-proneness of signals can serve as a handicap signal. In the first model, the direct handicap of sending a high-quality signal is not large enough to assure that a low-quality signaller will not send it. However, if the receiver sometimes mistakes a high-quality signal for a low-quality one, then there is an indirect handicap to sending a high-quality signal. The total handicap of sending such a signal may then still be such that a low-quality signaller would not want to send it. In the second model, there is no direct handicap of sending signals, so that nothing would seem to stop a signaller from always sending a high-quality signal. However, the receiver sometimes fails to detect signals, and this causes an indirect handicap of sending a high-quality signal that still stops the low-quality signaller of sending such a signal. The conditions for honesty are that the probability of an error of detection is higher for a high-quality than for a low-quality signal, and that the signaller who does not detect a signal adopts a response that is bad to the signaller. In both our models, we thus obtain the result that signal accuracy should not lie above a certain level in order for honest signalling to be possible. Moreover, we show that the maximal accuracy that can be achieved is higher the lower the degree of conflict between signaller and receiver. As well, we show that it is the conditions for honest signalling that may be constraining signal accuracy, rather than the signaller trying to make honest signals as effective as possible given receiver psychology, or the signaller adapting the accuracy of honest signals depending on his interests.

Attention↗

PubMed2006

The effects of memory load on the time course of inhibition of return.

Inhibition of return (IOR) refers to a processing disadvantage at a recently attended location. It is generally agreed that when elicited in a cue-target task, IOR will not be apparent until attention is disengaged from the originally cued location and returned to a neutral state. Here we test the hypothesis that when such disengagement is dependent on endogenous control, a secondary task that taxes working memory capacity should delay the appearance of IOR. Participants were given a six-item verbal working memory load prior to the peripheral cue in a cue-target detection task. Consistent with the hypothesis, the appearance of IOR was delayed on trials for which participants had to hold information in working memory. Converging evidence was derived from a second experiment in which the time course of IOR's appearance, when we added a central cue to exogenously remove attention from the peripheral cue, was unaffected by the memory load.

Attention↗

PubMed2004

Linguistic focus and good-enough representations: an application of the change-detection paradigm.

A number of lines of study suggest that word meanings are not always fully exploited in comprehension. In two experiments, we used a text-change paradigm to study depth of semantic processing during reading. Participants were instructed to detect words that changed across two consecutive presentations of short texts. The results suggest that the full details of word meanings are not always incorporated into the interpretation and that the degree of semantic detail in the representation is a function of linguistic focus. The results provide evidence for the idea that representations are only good enough for the purpose at hand (Ferreira, Bailey, & Ferraro, 2002).

Humans↗

PubMed1999

A limit in the processing of components in odour mixtures.

We investigated the hypothesis that physiological limitations restrict the ability of humans to identify components in an odour mixture. Subjects were trained to identify the test odours, and were required to detect a single highly familiar odorant in stimuli consisting of one, four, eight, twelve, and sixteen odorants by using a selective-attention procedure. The stimuli were delivered by a computer-controlled sixteen-channel air-dilution olfactometer which provided samples of each of the sixteen odorants to be of equal perceived intensity for each subject. Identification fell to chance level when sixteen odorants were present. It is proposed that the profound loss of information was primarily due to inhibition of olfactory receptor cells by the odorants through competitive mechanisms, and the subsequent loss of odour identity through changes in the spatial code that may be used to identify odorants.

Adolescent↗

PubMed2004

A detection-theoretic model of echo inhibition.

A detection-theoretic analysis of the auditory localization of dual-impulse stimuli is described, and a model for the processing of spatial cues in the echo pulse is developed. Although for over 50 years "echo suppression" has been the topic of intense theoretical and empirical study within the hearing sciences, only a rudimentary understanding of its mechanisms has emerged. In this article, psychometric functions and results from matching studies are used in developing a model that specifies the perceived position of the echo pulse as a normal deviate, with an expectation that is a logistic function of the echo delay and a variance that depends on interaural time difference. Loss of information in the echo event is quantified as a decline in the efficiency with which the binaural system receives information from the lag impulse.

Attention↗

PubMed2002

Visual detection is gated by attending for action: evidence from hemispatial neglect.

We report observations in patients with visual extinction demonstrating that detection of visual events is gated by attention at the level of processing at which a stimulus is selected for action. In one experiment, three patients reported the identity of numerical words and digits presented either in the ipsilesional field, the contralesional field, or both fields. On the critical bilateral trials, extinction was greater when the competing items shared the same meaning and response, regardless of whether the items were visually different (e.g., ONE + 1), or identical (e.g., 1 + 1). A fourth patient was tested in a second experiment in which the competing items on bilateral trials were either different (e.g., ONE + TWO), identical (e.g., ONE + ONE) or homophones that were visually and semantically different but shared the same response (e.g., ONE + WON). Homophones and identical items caused similar extinction with less extinction occurring on different item trials.

Aged↗

PubMed2004

Thorax vibrations of a stingless bee ( Melipona seminigra). II. Dependence on sugar concentration.

Using a laser vibrometer we studied the influence of the food's sugar concentration on different parameters of the thorax vibrations produced by foragers of Melipona seminigra during trophallaxis in the nest. The concentrations tested (20-70% sugar w/w) were within the biologically relevant range. They substantially influenced different parameters of the thorax vibrations. An increase of energy gains at the food source due to an increased sugar concentration was followed by an increase of both the pulse duration and the duty cycle and by a decrease of the pause duration between two subsequent pulses. These findings further support the hypothesis that the temporal pattern of the thorax vibrations reflects the energy budget of a foraging trip rather than food source distance. Likewise, the steep increase of pulse duration variability with sugar concentration is hard to reconcile with the assumption that pulse duration conveys reliable information about food source distance when bees collect at high-quality food sources.

Animal Communication↗

PubMed2005

A capability model of individual differences in frontal EEG asymmetry.

Researchers interested in measuring individual differences in affective style via asymmetries in frontal brain activity have depended almost exclusively upon the resting state for EEG recording. This reflects an implicit conceptualization of affective style as a response predisposition that is manifest in frontal EEG asymmetry, with the goal to describe individuals in terms of their general approach or withdrawal tendencies. Alternatively, the response capability conceptualization seeks to identify individual capabilities for approach versus withdrawal responses during emotionally salient events. The capability approach confers a variety of advantages to the study of affective style and personality, and suggests new possibilities for the approach/withdrawal motivational model of frontal EEG asymmetry and emotion. Logical as well as empirical arguments supportive of this conclusion are presented.

Adolescent↗

PubMed2006

The role of perceptual load in visual awareness.

Does awareness depend on attention? This is a fundamental issue for understanding the relationship of attention and awareness, yet previous research provided mixed results. Here, I describe new research that shows that the effects of attention on awareness depend on the level of perceptual load in the attended task. Awareness reports in both the inattentional blindness and change blindness paradigms were found to depend on the extent to which an attended primary task loads attention. Neuroimaging results revealed the involvement of frontoparietal attention network in awareness and transcranial magnetic stimulation experiments confirmed a causal role for frontoparietal activity in awareness. These results clarify the role of attention and associated frontoparietal activity in visual awareness within the framework of load theory of attention.

Attention↗

PubMed1999

A model of saccade generation based on parallel processing and competitive inhibition.

During active vision, the eyes continually scan the visual environment using saccadic scanning movements. This target article presents an information processing model for the control of these movements, with some close parallels to established physiological processes in the oculomotor system. Two separate pathways are concerned with the spatial and the temporal programming of the movement. In the temporal pathway there is spatially distributed coding and the saccade target is selected from a "salience map." Both pathways descend through a hierarchy of levels, the lower ones operating automatically. Visual onsets have automatic access to the eye control system via the lower levels. Various centres in each pathway are interconnected via reciprocal inhibition. The model accounts for a number of well-established phenomena in target-elicited saccades: the gap effect, express saccades, the remote distractor effect, and the global effect. High-level control of the pathways in tasks such as visual search and reading is discussed; it operates through spatial selection and search selection, which generally combine in an automated way. The model is examined in relation to data from patients with unilateral neglect.

Attention↗

PubMed2002

False memory and the discrepancy-attribution hypothesis: the prototype-familiarity illusion.

According to the discrepancy-attribution hypothesis (B. W. A. Whittlesea & L. D. Williams, 1998), people experience a feeling of familiarity when they perceive their processing to be surprising, but for an indefinite reason. This hypothesis has been successful in explaining several illusions of familiarity. Here, it is applied to the prototype-familiarity effect, an illusion of remembering that occurs when people are shown prototype words after studying lists of associates. The experiments showed that studying associates enhances semantic, but not perceptual, processing of prototypes. They also showed that claims of recognizing prototypes can be modified by presenting them in predictive or incongruous contexts at test. The evidence suggests that the effect results from an evaluation process that monitors the coherence of processing.

Association↗

PubMed1999

Spatial and semantic inhibitory processing in schizophrenia.

Two experiments assessed inhibitory mechanisms associated with the posterior and anterior attention networks in schizophrenia. Experiment 1 assessed the inhibition of return effect of the posterior network. Both healthy adults and schizophrenic adults showed inhibition of return, suggesting that this inhibitory mechanism of visual orienting is preserved in schizophrenia. Experiment 2 assessed semantic inhibition, which supposedly taps the anterior network, in a lexical-decision task. Healthy adults showed semantic inhibition effects in both visual fields. Schizophrenic adults showed semantic inhibition effects when targets were presented to the left visual field, involving the right hemisphere. However, semantic facilitation rather than inhibition was observed when targets were presented to the right visual field, involving the left hemisphere. These results reflect left hemisphere dysfunction associated with deficits in attentional control in schizophrenia.

Adult↗

PubMed2000

[Rehabilitation of homonymous hemianopsia].

BACKGROUND: Homonymous hemianopia, most often caused by cerebral arterial infarction, represents for the patient a severe handicap, whereby beside bumping into persons and objects disturbance of reading and writing are predominant. In the beginning the patients often are not aware of the hemianopia (anosognosia) or even completely deny it (hemi-neglect). For rehabilitation of homonymous hemianopia different successful methods are at disposal. METHODS: 1. Improvement of the patient's attention for the blind hemifield, 2. Enlargement of the saccadic search field. 3. Systematization of the search strategies, 4. Treatment of the hemianopic reading and writing disturbance, 5. Auxiliary optical measures. CONCLUSIONS: The rehabilitation of homonymous hemianopia with the described different methods is most successful and improves for the patient not only elementary and higher visual functions (visual exploration, reading and writing ability, parafoveal visual field, recognition of forms and colours), but may under favorable circumstances even restore partial or total working capacity.

Attention↗

PubMed2000

Distractor ratio influences patterns of eye movements during visual search.

We examined the flexibility of guidance in a conjunctive search task by manipulating the ratios between different types of distractors. Participants were asked to decide whether a target was present or absent among distractors sharing either colour or shape. Results indicated a strong effect of distractor ratio on search performance. Shorter latency to move, faster manual response, and fewer fixations per trial were observed at extreme distractor ratios. The distribution of saccadic endpoints also varied flexibly as a function of distractor ratio. When there were very few same-colour distractors, the saccadic selectivity was biased towards the colour dimension. In contrast, when most of the distractors shared colour with the target, the saccadic selectivity was biased towards the shape dimension. Results are discussed within the framework of the guided search model.

Eye Movements↗