On the time it takes to judge grammaticality

The presentation duration of five-word sequences was varied and participants were asked to judge their grammaticality. The five-word sequences were presented for a variable duration randomly selected between 50 and 500 ms with 50-ms steps and were immediately followed by a masking stimulus. Half of the sequences were correct sentences which were randomly intermixed with ungrammatical sequences formed of the same words in scrambled order. We measured the proportion of correct responses for each presentation duration in the grammatical and ungrammatical conditions, and calculated sensitivity and bias from these measures. Both the sensitivity measure ( d′) and the probability correct responses to grammatical and ungrammatical sequences increased as the stimulus duration increased, with a d′ of 2 and an average percent correct close to 87% for the grammatical sequences already attained at 300 ms. The rate of increase in performance diminished beyond 300 ms. Grammatical decision times were faster and more accurate for the grammatically correct sequences, thus indicating that participants were not responding by detecting illegal word combinations in the ungrammatical sequences. On the basis of these findings, we provide an upper estimate of 300 ms as the time it takes to access reliable syntactic information from five-word sequences in French, and we discuss the implications of this constraint for models of reading.

Masking the Detection of Taste Stimuli in Rats: NaCl and Sucrose

While psychophysical and neurophysiological assessments of taste sensitivity to single chemical compounds have revealed some fundamental properties of gustatory processing, taste stimuli are rarely ingested in isolation. Arguably, the gustatory system was adapted to identify and report the presence of numerous chemicals ingested concurrently. To begin systematically exploring the detectability of a target stimulus in a background in rodents, we used a gustometer to train rats in a 2-response operant task to detect either NaCl (n = 8) or sucrose (n = 8) dissolved in water, and then tested the sensitivity of rats to the trained NaCl stimulus dissolved in a sucrose masker (0.3, 0.6, or 1.0 M, tested consecutively) versus sucrose, or the trained sucrose stimulus dissolved in a NaCl masker (0.04, 0.2, or 0.4 M) versus NaCl. Detection thresholds (EC50 values) were determined for the target stimulus dissolved in each concentration of the masker. Except for 0.04 M NaCl, all masker concentrations tested increased the target stimulus EC50. Target stimulus detectability decreased systematically as masker concentrations increased. The shift in liminal sensitivity for either target was similar when the threshold for the masker was considered. At least for these prototypical stimuli, it appears that the attenuating impact of a masker on the detection of a target stimulus depends on sensitivity to the masking stimulus. Further study will be required to generalize these results and extend them to more complex maskers, and to discern neural circuits involved in the detection of specific taste signals in the context of noisy backgrounds.

Interference and visual masking

It is well known that a masking stimulus may reduce the visibility of a target stimulus. This has most commonly been attributed the mechanisms in the visual system. It has, however, become evident that a masking stimulus may reduce the stimulus power of a target. Such reductions which are in the stimuli have been explored in relation to spatial stimuli (Skottun, 2017, DOI:10.3758/s13428-017-0978-3; Skottun,2018. DOI: 10.1016/j.bbr.2018.04.016). An important aspect of visual masking is the effect of the relative temporal onset of the two stimuli (i.e., the Stimulus Onset Asynchrony, SOA). The present study sought to explore, using numerical analyses, how interference across time may manifest itself. By assuming some degree of temporal inaccuracy and a limited extent of temporal integration it was found that, depending on conditions, interference effects may take on the characteristics of either Type-A or Type-B masking. In connection with visual masking it is (tacitly) assumed that the target stimulus has the same stimulus power when presented in combination with a masking stimulus presented as when presented alone. It has earlier been shown that this cannot be assumed in connection with spatial stimuli. The present analyses make clear that this may also apply to stimuli presented at somewhat different times.

A new attempt to discover the covert recognition of faces

The article describes an experiment which used a new methodological approach to the study of covert recognition of faces by means of registration electro-dermal activity under short-term exposure of familiar and unfamiliar faces and the backward facelike masking stimulus. In contrast to previous studies the control of stimulus awareness allows us to evaluate not just the correct recognitions, but false alarms too. We used as the familiar faces not faces of the well-known persons, but faces of persons from the inner circle of subjects, including the subject’s own face. We confirmed the hypothesis that the characteristics of the electro-dermal reactions in response to familiar and unfamiliar faces will not be different in subjects with a high level of false alarms. However, for the group of subjects with practically zero false alarm rate and zero discriminability of familiar and unfamiliar faces an analysis of electro-dermal reactions have been mixed. On the one hand, as analysis on a group level showed, nor electrocutaneous reactions frequency, nor their amplitudes were not significantly different for the familiar and unfamiliar faces. On the other hand, it is clearly that these individual median and mean values of the amplitudes of subject's reactions are in average more than 2 times stronger when viewed familiar faces than viewed unfamiliar ones. These results leave a good chance to prove the effect of covert identification of faces in further experimentation with other groups of subjects

Metacontrast, target recovery, and the magno- and parvocellular systems: A perspective

In metacontrast a masking stimulus reduces the visibility of an adjacent target stimulus. This effect has been interpreted in terms of magno-/parvocellular interactions. It has also been found that a second masking stimulus, which precedes the primary mask by about 90 ms reduces the masking effect. This reduction, which is termed “target recovery,” has been hypothesized to reflect parvocellular inhibition of the magnocellular system. However, this is problematic because the time course of this effect is much larger than would be expected from magno-/parvocellular interactions. For this and other reasons, it is difficult to understand metacontrast in terms of magno- and parvocellular mechanisms.

Local Interactions in Neural Networks Explain Global Effects in Gestalt Processing and Masking

One of the fundamental and puzzling questions in vision research is how objects are segmented from their backgrounds and how object formation evolves in time. The recently discovered shine-through effect allows one to study object segmentation and object formation of a masked target depending on the spatiotemporal Gestalt of the masking stimulus (Herzog & Koch, 2001). In the shine-through effect, a vernier (two abutting lines) precedes a grating for a very short time. For small gratings, the vernier remains invisible while it regains visibility as a shine-through element for extended and homogeneous gratings. However, even subtle deviations from the homogeneity of the grating diminish or even abolish shine—through. At first glance, these results suggest that explanations of these effects have to rely on high-level Gestalt terminology such as homogeneity rather than on low-level properties such as luminance (Herzog, Fahle, & Koch, 2001). Here, we show that a simple neural network model of the Wilson-Cowan type qualitatively and quantitatively explains the basic effects in the shine-through paradigm, although the model does not contain any explicit, global Gestalt processing. Visibility of the target vernier corresponds to transient activation of neural populations resulting from the dynamics of local lateral interactions of excitatory and inhibitory layers of neural populations.

Effects of Stimulus Duration, Temporal Delay, and Complexity on the Judgments of Dot Location

The present study investigated how information on location was processed at an early stage of information processing by the task of recognizing dots presented briefly and followed by a masking stimulus. 8 subjects were asked on 1528 trials to recognize the positions of dots presented on a circumference. Effects of number of dots (1, 2, and 3), duration of presentation (36, 56, 200, and 500 msec.), and time delay (interval between the offset of display and the onset of recognition stimulus, 100 and 500 msec.) were examined. Analyses showed that the percentage of correct recognition increased with the duration of presentation and that the effect of duration decreased with the number of dots. Meanwhile, no significant effect was found for time delay. Consequently, with increased duration, the information on location is transferred to short-term visual memory. However, the ratio of transfer from iconic storage to short-term visual memory with duration varied with the complexity of visual stimulus.