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PubMed1998

Cooperativity, priming, and 3-D surface detection from optic flow.

Three experiments were conducted to determine whether the mechanisms responsible for the detection of three-dimensional (3-D) surfaces from optic flow operate in a cooperative manner. The first experiment was conducted to determine whether a hysteresis effect occurs for 3-D surface detection from optic flow. The results of the first experiment demonstrated a hysteresis effect with lower thresholds occurring for decreasing texture density than for increasing texture density. The second experiment used a priming methodology to determine whether this form of cooperativity was based on preactivation of shear detectors or preactivation of 2-D motion detectors. The results suggest that only shear detectors were primed. The third experiment utilized a similar methodology to determine whether a surface representation would produce a priming effect. We found no evidence that the priming effect found in the second experiment was the result of preactivation of a generic representation of the test stimuli. The results of the experiments, considered together, suggest priming of the mechanisms responsible for recovering shear.

Humans↗
PubMed2005

Distinctiveness and the recognition mirror effect: evidence for an item-based criterion placement heuristic.

Superior detection and rejection of 1 versus another class of items during recognition is called the mirror effect. Some mirror effects may involve strategic criterion adjustments based on item distinctiveness and its relation to memorability. Three experiments demonstrated mirror effects for known versus unknown scenes and 1 suggested a similar pattern for faces. In opposition to preexperimental familiarity, lures from known and frequently encountered locations were confidently rejected more often than unknown lures. Forgetting and speeding recognition reversed this lure response pattern, suggesting abandonment of strategic adjustment in favor of a single fixed criterion. With sufficient response time and recent encoding, observers demand more evidence for conceptually distinctive items, perhaps because such items typically foster vivid recollection during retrieval.

Cues↗
PubMed2004

Signal detection theory applied to three visual search tasks--identification, yes/no detection and localization.

Adding distracters to a display impairs performance on visual tasks (i.e. the set-size effect). While keeping the display characteristics constant, we investigated this effect in three tasks: 2 target identification, yes-no detection with 2 targets, and 8-alternative localization. A Signal Detection Theory (SDT) model, tailored for each task, accounts for the set-size effects observed in identification and localization tasks, and slightly under-predicts the set-size effect in a detection task. Given that sensitivity varies as a function of spatial frequency (SF), we measured performance in each of these three tasks in neutral and peripheral precue conditions for each of six spatial frequencies (0.5-12 cpd). For all spatial frequencies tested, performance on the three tasks decreased as set size increased in the neutral precue condition, and the peripheral precue reduced the effect. Larger set-size effects were observed at low SFs in the identification and localization tasks. This effect can be described using the SDT model, but was not predicted by it. For each of these tasks we also established the extent to which covert attention modulates performance across a range of set sizes. A peripheral precue substantially diminished the set-size effect and improved performance, even at set size 1. These results provide support for distracter exclusion, and suggest that signal enhancement may also be a mechanism by which covert attention can impose its effect.

Attention↗
PubMed2004

Detection of repeated trigrams: evidence of all-or-none learning.

Two experiments investigated trigram detection in a continuous recognition task. In Experiment 1 consonant trigrams were presented visually, one at a time, with occasional repetition of a trigram after an interval of 0, 2, 4, 8, or 16 other trigrams. Subjects were told to respond with a button press every time they saw a repeated trigram. If a subject responded to a repeated trigram, it was not repeated again. However, if a subject did not respond to a repeated trigram, it was repeated again at the same interval for up to 3 repetitions. For all intervals greater than 0, the probability of noticing a repeated trigram did not increase with the number of repetitions. In Experiment 2 meaningless shape trigrams were presented, and occasionally a trigram was repeated after an interval of 0, 1, or 2 trigrams. For both intervals greater than 0, the probability of noticing a repeated trigram did not increase with the number of repetitions. The results demonstrate that a repeated input does not necessarily leave a permanent trace in memory.

Adult↗
PubMedDate not supplied

Can we resolve contradictions between process dissociation models?

Wainwright and Reingold (1996) presented equations for various versions of the process dissociation procedure that has been used to separate conscious and unconscious memory process. In the present reply it is suggested that these equations, though helpful, may not capture some of the key theoretical possibilities that could help to resolve apparent contradictions and paradoxes in the empirical literature. Specifically, there could be an independence of processes that might be estimated to a sufficient degree of accuracy for some theoretical purposes despite a violation of the assumption of stochastic independence.

Humans↗
PubMed2001

Lorazepam and diazepam impair true, but not false, recognition in healthy volunteers.

RATIONALE: The deleterious effects of benzodiazepine on memory are well documented. However, their effects on false memories are unknown. OBJECTIVE: The aim of this study was to investigate the effects of lorazepam and diazepam on false memories and related states of awareness in healthy volunteers. METHODS: The Deese/Roediger-McDermott procedure was used in 36 healthy volunteers randomly assigned to one of three parallel groups (placebo, diazepam 0.3 mg/kg, lorazepam 0.038 mg/kg). Subjects studied lists of words semantically related to a non-presented theme word (critical lure). On a recognition memory task with both previously presented words and non presented critical lures, they were asked to give Remember, Know or Guess responses to items that were recognized on the basis of conscious recollection, familiarity, or guessing, respectively. RESULTS: The proportions of studied words correctly recognized and the proportions of Remember responses associated with true recognition were lower in the benzodiazepine groups than in the placebo group. In contrast, benzodiazepines did not significantly influence the proportions of critical lures falsely recognized or the proportions of Remember responses associated with false recognition. CONCLUSION: These results indicate that diazepam and lorazepam impair conscious recollection associated with true, but not false, memories.

Adolescent↗
PubMed2002

Functional decay of memory for tasks.

Correct performance often depends on remembering the task one has been instructed to do. When the task periodically changes, memory for the current task must decay (lose activation) to prevent it from interfering with memory for the next task when that is encoded. Three task-switching experiments examine this decay process. Each shows within-run slowing, a performance decline occurring as memory for the current task decays. In experiment 1, slowing is attenuated when memory for the task is optional, suggesting that memory is indeed causal. Experiment 2 finds slowing despite a flat hazard rate for task instructions, suggesting that slowing is not an artifact of instruction anticipation. Experiment 3 finds slowing in the familiar alternating-runs paradigm (Rogers & Monsell, 1995), suggesting that it may lurk elsewhere. A process model of activation explains within-run slowing and relates it to switch cost and "restart cost" (Allport & Wylie, 2000) in functional terms.

Analysis of Variance↗
PubMed2005

Mechanical frequency and stimulation-site-related differences in vibrotactile detection capacity along the lip vermilion in young adults.

Accurate clinical assessment of the infraorbital and mental branch of the trigeminal nerve is aided by an appreciation of the variations in sensitivity that may exist along the surface of the perioral region under examination. The purpose of this investigation was to map the mediolateral spatial and frequency variations in vibrotactile detection capacity to inputs delivered to the upper lip (UL) and lower lip (LL) vermilion. Mechanical vibrotactile inputs at frequencies of 5, 10, 50, and 150 Hz were delivered to three locations on the vermilion of the UL and LL: midsagittally and laterally (left and right) at a point halfway between the midsagittal plane and the oral angle. An adapted staircase tracking method was used to converge upon a threshold value for each test frequency at each stimulation site. The results indicated that midsagittal vermilion sites were significantly more sensitive to our range of vibrotactile inputs compared to lateral vermilion locations. In addition, no significant differences in sensitivity as a function of laterality or between the UL and LL vermilion sites were noted. Greater midline sensitivity to vibrotactile stimulation suggests that receptive fields at this location may be of greater density and/or demonstrate greater overlap compared to lateral vermilion sites.

Adult↗
PubMed2005

Domestic dogs (Canis familiaris) use a physical marker to locate hidden food.

Dogs can use the placement of an arbitrary marker to locate hidden food in an object-choice situation. We tested domestic dogs (Canis familiaris) in three studies aimed at pinning down the relative contributions of the human's hand and the marker itself. We baited one of two cups (outside of the dogs' view) and gave the dog a communicative cue to find the food. Study 1 systematically varied dogs' perceptual access to the marker placing event, so that dogs saw either the whole human, the hand only, the marker only, or nothing. Follow-up trials investigated the effect of removing the marker before the dog's choice. Dogs used the marker as a communicative cue even when it had been removed prior to the dog's choice and attached more importance to this cue than to the hand that placed it although the presence of the hand boosted performance when it appeared together with the marker. Study 2 directly contrasted the importance of the hand and the marker and revealed that the effect of the marker diminished if it had been associated with both cups. In contrast touching both cups with the hand had no effect on performance. Study 3 investigated whether the means of marker placement (intentional or accidental) had an effect on dogs' choices. Results showed that dogs did not differentiate intentional and accidental placing of the marker. These results suggest that dogs use the marker as a genuine communicative cue quite independently from the experimenter's actions.

Animals↗
PubMed2005

A re-examination of the effects of biased lineup instructions in eyewitness identification.

A meta-analytic review of research comparing biased and unbiased instructions in eyewitness identification experiments showed an asymmetry, specifically that biased instructions led to a large and consistent decrease in accuracy in target-absent lineups, but produced inconsistent results for target-present lineups, with an average effect size near zero (N. M. Steblay, 1997). The results for target-present lineups are surprising, and are inconsistent with statistical decision theories (i.e., D. M. Green & J. A. Swets, 1966). A re-examination of the relevant studies and the meta-analysis of those studies shows clear evidence that correct identification rates do increase with biased lineup instructions, and that biased witnesses make correct identifications at a rate considerably above chance. Implications for theory, as well as police procedure and policy, are discussed.

Bias↗
PubMed2006

Detectability decreases with off-normal viewing in medical liquid crystal displays.

RATIONALE AND OBJECTIVES: To quantify the reduction in detection performance of subtle signals at off-normal viewing directions in medical active-matrix liquid crystal displays (AMLCDs). MATERIALS AND METHODS: Fifty synthetic image pairs per viewing condition (a total of 350) were used in a two-alternative forced-choice experiment in which 11 trained observers viewed images at 0, 30, and 45 degrees from the display normal, along the diagonal axis of a 5 million pixel in-plane switching monochrome AMLCD. The images were generated using white-noise backgrounds. A Gaussian signal was added to the signal-present set with three different signal amplitudes (4, 8, and 12 gray levels in a 10-bit scale). RESULTS: The average percent correct achieved for a signal of 4 gray levels was 79.6 (95% confidence intervals based on reader and case variability: 71.6-86.9), 63.4 (CI 56.0-71.3), and 55.3 (CI 48.4-62.0), for 0, 30 and 45 degrees from the display normal, respectively. When the signal amplitude was increased by a factor of two, the performance was 76.9 and 57.0 for 30 and 45 degrees, respectively, and 95.3 and 85.3 when the amplitude was increased by a factor of three. The observers took on average about twice as long and as much as seven times as long to reach decisions in off-normal viewing. CONCLUSIONS: Off-normal viewing of diagnostic images in AMLCDs significantly reduces the detection of low-contrast abnormalities. Increased off-normal signal amplitudes were required to regain the detection performance measured for normal viewing. We observed this decrease in detection performance for off-normal viewing even when measured decision times were about twice as long as for normal viewing.

Computer Terminals↗
PubMed2005

Signal evolution in prey recognition systems.

In this paper a graphical model first developed in the context of kin recognition is adapted to the study of signalling in predator-prey systems. Antipredation strategies are envisioned as points along a signal-to-noise (S/N) axis, with concealing (low S/N) and conspicuous (high S/N) strategies being placed at opposite sides of this axis. Optimal prey recognition systems should find a trade-off between acceptance errors (going after a background cue as if it were a prey) and rejection errors (not going after a prey as if it were background noise). The model also predicts the types of cues the predator should use in opposite sides of the S/N axis.

Animals↗
PubMed2006

Signal-to-noise ratio of chemosensory event-related potentials.

OBJECTIVE: We investigated the influence of the number of stimuli on signal-to-noise (S/N) ratio of CSERP. METHODS: CSERP from 20 normosmic subjects were obtained in response to stimulation with two olfactory (H(2)S and PEA) and a trigeminal (CO(2)) stimulant. For each of these odors, 160 stimuli were delivered into the right nostril (duration 200ms, mean ISI 30s) using a constant-flow, air-dilution olfactometer. For each EEG recording site (Fz, Cz, Pz, C3, C4), peak-to-peak amplitude N1P2 and noise amplitude levels were determined. Subsequently, S/N ratios were calculated. RESULTS: The S/N ratios for olfactory ERP generally improved for H(2)S and PEA. For responses to PEA, S/N ratios increased significantly up to 80 averages (S/N ratio=5.6). The number of stimuli for an optimal S/N ratio for trigeminal ERP was slightly lower, i.e. 60 averages (S/N ratio=7.9). CONCLUSIONS: S/N N1P2 ratios in olfactory and trigeminal ERP significantly improve with an increasing number of responses averaged under these experimental conditions. This is mainly due to a reduction of noise level. Applying more stimuli has little additional effect on S/N ratio due to a concomitant decrease in signal amplitude. SIGNIFICANCE: An optimal S/N ratio is essential when recording CSERP in neurodegenerative disorders, where responses may be of low amplitude, and for medico-legal purposes.

Adolescent↗
PubMed2006

fMRI in alert, behaving monkeys: an adaptation of the human infant familiarization novelty preference procedure.

Functional magnetic resonance imaging (fMRI) is increasingly used in non-human primate research. In the present study, we adapt the familiarization-novelty preference (FNP) procedure used in human infant research to examine visual behavior in alert, unanaesthetized rhesus monkeys that were acclimated to the fMRI environment, but did not undergo behavioral training. In keeping with the typical FNP paradigm, we recorded eye movements (looking time and number of fixations) while monkeys viewed a series of four identical pictures (familiarization phase) followed by two different pictures (novelty phase). Number of fixations and looking time both increased during the novelty phase, thereby demonstrating visual discrimination of the new from the old picture. Importantly, discrimination did not occur on catch trials in which six identical pictures were presented. Moreover, brain activation in the amygdala was more strongly associated with the novelty phase than with the familiarization phase. In addition, magnitude of brain activation in the amygdala was correlated with the behavioral effect of visual discrimination. These findings demonstrate the feasibility of using eye movements as an index of visual discrimination in untrained monkeys during fMRI scanning. This methodological approach helps to extend the repertoire of research tools for fMRI in non-human primates.

Adaptation, Physiological↗
PubMed2006

Detection of nonlinear event-related potentials.

The methods used to evaluate event-related potentials (ERPs) are generally insensitive to nonlinear responses. Our goal was to show that nonlinear ERPs could be detected using recurrence analysis (RA). When fixed-phase sine signals were added to baseline electroencephalograms (EEGs), the added linear determinism was detected by signal averaging, as expected, and by RA. However, when nonlinear determinism was simulated by adding either random-phase sine or Lorenz signals, the added signals were detected only by RA. Auditory evoked potentials (AEPs) were studied in five subjects using RA. We detected not only the characteristic linear effects caused by onset and offset of the sound, but also nonlinear AEPs not previously reported; they occurred at 473-661 ms after onset, and 282-602 ms after offset, depending on the subject. In five other subjects we found nonlinear magnetosensory evoked potentials; they occurred at 209-354 ms after field onset, depending on the subject. RA was less sensitive than time averaging for detecting linear ERPs, but had the advantage of being able to detect nonlinear ERPs.

Acoustic Stimulation↗
PubMed2006

False recognition of incidentally learned pictures and words in primary progressive aphasia.

Recognition memory was tested in patients with primary progressive aphasia (PPA), a language based dementia with relative preservation of memory for at least the first 2 years. The goal of the study was two-fold: (1) to compare true and false recognition rates for words versus pictures in patients with PPA and cognitively intact controls and (2) to determine if the semantic relatedness of distracters-to-targets influences recognition memory performance. Overall, performance of PPA patients was worse for words than pictures. PPA patients and healthy elderly controls showed similar recognition rates for studied items. However, the patients had significantly more false alarms than controls, particularly to semantically related items. This suggests that the aphasia in PPA patients contributes to their difficulty in selecting among items within a semantic class.

Aged↗
PubMed2005

Change blindness: past, present, and future.

Change blindness is the striking failure to see large changes that normally would be noticed easily. Over the past decade this phenomenon has greatly contributed to our understanding of attention, perception, and even consciousness. The surprising extent of change blindness explains its broad appeal, but its counterintuitive nature has also engendered confusions about the kinds of inferences that legitimately follow from it. Here we discuss the legitimate and the erroneous inferences that have been drawn, and offer a set of requirements to help separate them. In doing so, we clarify the genuine contributions of change blindness research to our understanding of visual perception and awareness, and provide a glimpse of some ways in which change blindness might shape future research.

Attention↗