1,720,996 research outputs found
Individual differences in subjective experience and objective performance in metacontrast masking
No full textWhen participants discriminate stimuli that are masked by a following stimulus via metacontrast masking, stable individually different masking functions have been found despite identical stimulation conditions.In the present study, in one group of observers objective performance increased with increasing target-mask stimulus onset asynchrony (SOA), whereas in another group performance decreased with increasing SOA. In addition, a group of overachievers showed ceiling effects whereas a group of underachievers hardly exceeded chance levels of performance irrespective of SOA. The differences between observers' objective measures of performance correspond to differences in participants' phenomenological reports of subjective experience. This indicates that participants differ in their access to specific perceptual cues that they use spontaneously to solve the task. When we instructed participants to use only one specific cue, the instructed cue determined participants' objective performance considerably in two experiments. Nevertheless, masking functions remained similar with and without the cued instruction, and the effect of cues depended on the initial masking function of individuals. Findings suggest that individuals with different masking functions differ also in terms of phenomenology, used cues, and response strategy. The relation between subjective experience, reported usage of perceptual cues, and objective performance in the metacontrast masking task deserves further investigation
PERCEPTUAL CUES MODULATE RESPONSE CUE EFFECTS ON FRONTAL N200 AMPLITUDE AND RESPONSE ACTIVATION
No full textIndividual differences in metacontrast masking regarding sensitivity and response bias
No full textIn metacontrast masking target visibility is modulated by the time until a masking stimulus appears. The effect of this temporal delay differs across participants in such a way that individual human observers’ performance shows distinguishable types of masking functions which remain largely unchanged for months. Here we examined whether individual differences in masking functions depend on different response criteria in addition to differences in discrimination sensitivity. To this end we reanalyzed previously published data and conducted a new experiment for further data analyses. Our analyses demonstrate that a distinction of masking functions based on the type of masking stimulus is superior to a distinction based on the target–mask congruency. Individually different masking functions are based on individual differences in discrimination sensitivities and in response criteria. Results suggest that individual differences in metacontrast masking result from individually different criterion contents
Individually different weighting of multiple processes underlies effects of metacontrast masking
No full textMetacontrast masking occurs when a mask follows a target stimulus in close spatial proximity. Target visibility varies with stimulus onset asynchrony (SOA) between target and mask in individually different ways leading to different masking functions with corresponding phenomenological reports. We used individual differences to determine the processes that underlie metacontrast masking. We assessed individual masking functions in a masked target discrimination task using different masking conditions and applied factor-analytical techniques on measures of sensitivity. Results yielded two latent variables that (1) contribute to performance with short and long SOA, respectively, (2) relate to specific stimulus features, and (3) differentially correlate with specific subjective percepts. We propose that each latent variable reflects a specific process. Two additional processes may contribute to performance with short and long SOAs, respectively. Discrimination performance in metacontrast masking results from individually different weightings of two to four processes, each of which contributes to specific subjective percepts
PERCEPTUAL CUES MODULATE RESPONSE CUE EFFECTS ON FRONTAL N200 AMPLITUDE AND RESPONSE ACTIVATION
No full textIndividual differences in metacontrast masking: A call for caution when interpreting group data
No full textIn this issue of Consciousness and Cognition, Bachmann (2010) comments on our study (Albrecht, Klapötke, & Mattler, 2010), which revealed two groups of observers with qualitative individual differences in metacontrast masking that are enhanced by perceptual learning. We are pleased that our study receives this attention and even more about Bachmann’s extremely positive comments. In this invited reply we argue that observers seem to be similar only at the beginning of the experiment but they have no choice as to which group to join. Findings strongly recommend to look at the data of individual subjects
Evidence from metacontrast masking
No full textA metacontrast masking paradigm was employed to provide evidence for the richness and diversity of our visual experience. Square- and diamond-shaped targets were followed by square- and diamond-shaped masks at varying stimulus onset asynchronies (SOAs), resulting in shape-congruent and shape-incongruent trials. In Experiment 1, participants reported in each trial how they perceived target and mask. After extended training, seven different aspects of the target could be distinguished as specific percepts in this metacontrast masking paradigm. These percepts encompass aspects including the temporal distance between both stimuli, the perceived contrast of the target, and motion percepts resulting from the interplay between the target and mask. Participants spontaneously reported each of these percepts, and the frequency of reports varied systematically with SOA and the congruency between target and mask. In Experiment 2, we trained a new group of participants to distinguish each of these target percepts. Again, the frequency of reports of the specific percepts varied with SOA and congruency, just as in Experiment 1. In a last session, we measured objective discrimination performance yielding the typical individually different masking functions across SOAs. An examination of the relation between the frequencies of reports of subjective percepts and objective discrimination performance revealed multiple dissociations between these measures. Results suggest a multidimensional pattern of subjective experiences under metacontrast, which is reflected in dissociated subjective and objective measures of visual awareness. As a consequence, awareness cannot be assessed exhaustively by a single measure, thus challenging the use of simple one-dimensional subjective or objective measures in visual masking
Metacontrast masking does not change with different display technologies: A comparison of CRT and LCD monitors
No full textAbstract Most vision labs have had to replace the formerly dominant CRT screens with LCDs and several studies have investigated whether changing the display type leads to changes in perceptual phenomena, since fundamental properties of the stimulation, e.g., the transition time between frames, differ between these different display technologies. While many phenomena have proven robust, Kihara et al. (2010) reported different metacontrast masking functions on LCDs compared to CRTs. This difference poses a challenge for the integration of new LCD-based findings with the established knowledge from studies with CRTs and requires theoretical accounts that consider the effects of different display types. However, before further conclusions can be drawn, the basic findings should be secured. Therefore, we tried to reproduce the display type effect by comparing metacontrast masking on an LCD and a CRT in two experiments. Our approach differs from the previous study by increasing the power and reliability of the measurements and carefully matching the two display types. In addition to display type, we varied target-mask stimulus-onset asynchrony (SOA) and stimulus-background polarity. Regardless of display type and polarity, we found the typical type-B masking functions. Evidence for a SOA-dependent display type effect in the black-on-white polarity condition from Experiment 1 was not replicated in Experiment 2. Overall, the results indicate that metacontrast masking effects on objective and subjective measurements, i.e., discriminatory sensitivity and phenomenological reports, do not vary significantly with display technologies. This lack of display effects is discussed in the context of current theories of metacontrast masking
Long-lasting effects of briefly flashed words and pseudowords in ultrarapid serial visual presentation.
No full textOur ability to identify even complex scenes in rapid serial visual presentation (RSVP) is astounding, but memory for such items seems lacking. Rather than pictures, we used streams of more than 200 verbal stimuli, rushing by on the screen at a rate of more than 12 items per second while participants had to detect infrequent names (Experiments 1 and 2) or words written in capitals (Experiment 3). By direct and indirect tests, we investigated what is remembered of these masses of task-irrelevant distractor words and pseudowords embedded in an RSVP stream. Lexical decision, the indirect test applied either immediately after each stimulus train or with a delay, revealed strong long-term priming effects. Relative to stimuli not shown before, lexical decisions were faster and more accurate to words but slower to pseudowords. The size of these effects mirrored how often words and pseudowords had occurred in a stream, suggesting that memory traces are strengthened with successive presentations and survive for several minutes at least. Moreover, in a direct test (old new categorization), words as well as pseudowords benefited from prior occurrence in an RSVP stream if they had occurred more than once. These findings parallel recent physiological and behavioral evidence for memory consolidation of distractor pictures in RSVP and highlight that, despite huge numbers of interfering stimuli, distractor words and pseudowords exhibit long-lasting memory effects. Consolidation seems to progress at higher cognitive levels at the same time that subsequent stimuli are perceptually processed
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