Discrimination of compound stimuli involving the presence or absence of a distinctive visual feature

Pigeons learned a free operant, go/no-go discrimination between stimuli produced by rapid alternation of different features on the response key. The 0 degrees -B compound consisted of a vertical black line on a white background (the 0 degrees feature) alternated with a blank white field (the B feature), with successive 0.75-sec feature on periods separated by 0.20-sec dark periods. Pecks at the alternating 0 degrees and B features were recorded separately. When pecks at the 0 degrees -B compound were reinforced and pecks at the B-B stimulus (repeated brief presentations of the B feature) were extinguished, the birds pecked more at the 0 degrees feature than at the B feature in the 0 degrees -B compound; subsequently, decremental line-tilt generalization gradients were obtained. When pecks at B-B were reinforced and pecks at 0 degrees -B were extinguished, the rate of pecking at the 0 degrees feature decreased to a low level much more rapidly than did the rate of pecking at the B feature in the 0 degrees -B compound; incremental line-tilt gradients were obtained. Following training with pecks at 0 degrees -B reinforced and pecks at 0 degrees -0 degrees extinguished, incremental line-tilt gradients were obtained, whereas the gradients were decremental following training with 0 degrees -0 degrees reinforced and 0 degrees -B extinguished.     

Velocities of motor and sensory nerve conduction are the same for right and left arms in right- and left-handed normal subjects

The velocities of motor and sensory conduction of median and ulnar nerves were measured on the left and right arms of 33 right-handed and 12 left-handed normal subjects. Contrary to current knowledge there was no statistically significant difference in the velocities of nerve conduction on the left and right sides of these subjects. It was suggested that the differences in the velocities of nerve conduction cannot contribute to the mechanisms of handedness.     

Intact visual discrimination of complex and feature-ambiguous stimuli in the absence of perirhinal cortex

The perirhinal cortex is known to be important for memory, but there has recently been interest in the possibility that it might also be involved in visual perceptual functions. In four experiments, we assessed visual discrimination ability and visual discrimination learning in severely amnesic patients with large medial temporal lobe lesions that included complete lesions of perirhinal cortex. Experiment 1 tested complex visual object perception. Experiments 2a and 2b tested in two different ways the ability to discriminate between feature-ambiguous images, which was reported to be impaired in monkeys with perirhinal lesions. Experiment 3 involved images that were successfully discriminated in Experiment 2a and asked patients to learn across 20 trials which of the images had been designated as "correct." Patients performed as well as controls in Experiments 1, 2a, and 2b, but one of the patients had difficulty in Experiment 3 when the task required remembering from trial to trial which image was "correct." These findings indicate that perirhinal cortex is not needed for visual perception across a wide range of visual perceptual tasks.     

Differential responding in the presence and absence of discriminative stimuli during multielement functional analyses

We evaluated the extent to which discriminative stimuli (S(D)s) facilitate differential responding during multielement functional analyses. Eight individuals, all diagnosed with mental retardation and referred for assessment and treatment of self-injurious behavior (SIB) or aggression, participated. Functional analyses consisted of four or five assessment conditions alternated in multielement designs. Each condition was initially correlated with a specific therapist and a specific room color (S(D)s), and sessions continued until higher rates of target behaviors were consistently observed under a specific test condition. In a subsequent analysis, the programmed S(D)s were removed (i.e., all conditions were now conducted by the same therapist in the same room), and sessions continued until differential responding was observed or until twice as many sessions were conducted with the S(D)s absent (as opposed to present), whichever came first. Results indicated that the inclusion of programmed S(D)s facilitated discrimination among functional analysis conditions for half of the participants. These results suggest that the inclusion of salient cues may increase either the efficiency of functional analyses or the likelihood of obtaining clear assessment outcomes.     

Target locations in visual field and character recognition by students of Chinese

The potential influence of target location in a visual field on search should be considered in layouts of control panels and advertisements. This investigation was done to verify the assumption that the upper-left portion of a page or its equivalent naturally attracts the attention of the viewer. Exp. 1 used a tachistoscope to test which of eight Chinese characters first attracted the attention of viewers. The eight Chinese characters are arranged in a square and a circular configuration. In the square layout, a large square (18 cm x 18 cm) was first conceptually subdivided into nine equal parts (6 cm x 6 cm). Then, the eight Chinese characters were put in the center of each part, leaving the central part blank. In the circular layout, the same Chinese characters were symmetrically placed on the conceptual circumference (r = 6 cm) of a circle within a large square. Exp. 2 was a paper-and-pencil test. An embedded-fault-character-search was used to examine the location of the first faulty character discovered by the subjects. 60 college students and 36 schoolchildren were selected as subjects for the tachistoscopic experiment and paper-and-pencil test. Finally, five graduate students participated in Exp. 3 in which an eye camera registered subjects' eye movements to measured distribution of durations of looking over eight locations. The measurements indicated a slight predominance of the upper-left portion for college students and graduate students, and a slight predominance of the upper-right portion for schoolchildren.     

Facilitation and disruption of lateralized syllable processing by unattended stimuli in the opposite visual field

The influence of lateralized unattended stimuli on the processing of attended stimuli in the opposite visual field can shed light on the nature of information that is transferred between hemispheres. On a cued bilateral task, participants tried to identify a syllable in the attended visual field, which elicits a left hemisphere (LH) advantage and different processing strategies by the two hemispheres. The same or a different syllable or a neutral stimulus appeared in the unattended field. Transmission of unattended syllable codes between hemispheres is symmetric, as revealed by equal interference for the two visual fields. The LH is more accurate than the RH in encoding unattended syllables, as indicated by facilitation in the left but not right visual field and a greater frequency of identifiable intrusions into the left than right field. However, asymmetric encoding strategies are different for attended and unattended syllables.     

Effects of attention on localization of stimuli in the visual field

Subjects localized a small letter that appeared inside one of three large circles that was either validly or invalidly cued. The results indicated that, although unattended stimuli were localized fairly accurately, attention still improved localization. Moreover, the results revealed a greater dispersion of localization responses along the horizontal axis and also showed that mislocalization of attended peripheral stimuli is biased toward the periphery.     

Asymmetries in infants' attention to the presence or absence of features

Three experiments were performed to test whether infants show a bias for detecting the presence of a feature in a stimulus rather than its absence. In the 1st experiment, 24 16-week-old infants were given 3 paired-comparison problems, each of which included a 25-s familiarization phase followed by 2 test trials. Infants were familiarized to 1 member of a set of capital alphabetical letters (E-F; Q-O; B-R). Then they were given a paired-comparison recognition test under 1 of 2 conditions. In the feature-present condition, the familiar letter (e.g., F) was paired with a novel letter containing the addition of a distinguishing element (e.g., E). In the feature-absent condition, infants were presented with a familiar letter (e.g., E) paired with a novel letter in which 1 element was removed (e.g., F). Infants showed a novelty preference to the letter in which the distinguishing feature was present, but there was no preference for novelty in the feature-absent condition. The 2nd experiment showed that infants' fixation to the letter containing the presence of the feature was not due to a simple preference for the letter with the greater number of elements. Finally, to test whether infants' failure to discriminate the absence was due to insufficient encoding time, 36 infants were tested in a 3rd experiment in which familiarization time was varied. After 20 s of familiarization, no evidence of discrimination was observed in either the feature-present or feature-absent condition. After 30 s, however, infants could discriminate the novel letter in the feature-present condition but not in the feature-absent condition. The significance of these results is discussed in terms of theoretical explanations for the development of the feature-presence bias.     

Ratings of emotion in faces are influenced by the visual field to which stimuli are presented

This experiment was designed to assess the differential impact of initially presenting affective information to the left versus right hemisphere on both the perception of and response to the input. Nineteen right-handed subjects were presented with faces expressing happiness and sadness. Each face was presented twice to each visual field for an 8-sec duration. The electro-oculogram (EOG) was monitored and fed back to subjects to train them to keep their eyes focused on the central fixation point as well as to eliminate trials confounded by eye movement artifact. Following each slide presentation, subjects rated the intensity of the emotional expression depicted in the face and their emotional reaction to the face on a series of 7-point rating scales. Subjects reported perceiving more happiness in response to stimuli initially presented to the left hemisphere (right visual field) compared to presentations of the identical faces to the right hemisphere (left visual field). This effect was predominantly a function of ratings on sad faces. A similar, albeit less robust, effect was found on self-ratings of happiness (the degree to which the face elicited the emotion in the viewer). These data challenge the view that the right hemisphere is uniquely involved in all emotional behavior. The implications of these findings for theories concerning the lateralization of emotional behavior are discussed.     

Target size and luminance in apparent brightness of the peripheral visual field.

Four target sizes between 15 and 120 min. of arc with six luminance levels covering the range between 398.1 and 1.26 cd/m2 in steps of .5 log units were presented to 0, 20, 40, 60, and 80 degrees nasal retinal loci. In both peripheral and foveal viewing, magnitude estimates to apparent brightness judged by 12 Ss changed as a function of target size and luminance. The exponent of the power function was not dependent on retinal loci but on target size. However, when target size increased, the apparent brightness was slightly greater with peripheral viewing than with foveal viewing.     

Interhemispheric transfer of figural information in right- and non-right-handed subjects.

The capacity of normal human Ss to match abstract shapes across the cerebral hemispheres was studied as a function of exposure duration. A general right hemisphere superiority was found, and in the conditions where one stimulus was presented to each hemisphere, the order of stimuli (to the right or left hemisphere first) did not affect performance. Decreasing stimulus exposure was shown to interact with hemisphere differences. An overall superiority of non-right-handed subjects was found, although their pattern of results did not differ from right-handed Ss, and it is argued that this supports the hypothesis that the cerebral organisation of the non-right-hander is more diffuse in its general organisational structure.     

Attentional control in visual signal detection: effects of abrupt-onset and no-onset stimuli

The attention literature distinguishes two general mechanisms by which attention can benefit performance: gain (or resource) models and orienting (or switching) models. In gain models, processing efficiency is a function of a spatial distribution of capacity or resources; in orienting models, an attentional spotlight must be aligned with the stimulus location, and processing efficiency is a function of when this occurs. Although they involve different processing mechanisms, these models are difficult to distinguish empirically. We compared performance with abrupt-onset and no-onset Gabor patch stimuli in a cued detection task in which we obtained distributions of reaction time (RT) and accuracy as a function of stimulus contrast. In comparison to abrupt-onset stimuli, RTs to miscued no-onset stimuli were increased and accuracy was reduced. Modeling the data with the integrated system model of Philip L. Smith and Roger Ratcliff (2009) provided evidence for reallocation of processing resources during the course of a trial, consistent with an orienting account. Our results support a view of attention in which processing efficiency depends on a dynamic spatiotemporal distribution of resources that has both gain and orienting properties.     

Discrimination of auditory target dimensions in the presence or absence of variation in a second dimension by infants

Discrimination of two acoustic dimensions of auditory stimuli, vowel identity and pitch contour, was tested with infants between the ages of 4 and 16 weeks using the high-amplitude sucking (HAS) technique. Discrimination of the vowel dimension and the pitch dimension was tested under two conditions: when a change in the target dimension occurred in theabsence of constant variation in a second dimension, and when a change in the target dimension occurred in thepresence of constant variation in a second dimension. In addition, discrimination was tested in a combined condition in which one level of the vowel dimension was always combined with one level of the pitch dimension and the stimulus change to be detected was a recombination of the levels of each dimension. Sucking-recovery scores demonstrated that infants always discriminated a change in the target dimension when it occurred without variation in the second dimension, regardless of the dimension that served as the target. However, while variation of the pitch dimension did not alter vowel discrimination, variation in the vowel dimension interfered with discrimination of the pitch dimension. Discrimination was also not evidenced in the combined condition. Analysis of the group time-to-habituation (TH) data revealed that significantly longer TH scores were correlated with a failure to demonstrate discrimination. The data are discussed in terms of the formation of auditory perceptual categories in early infancy as they relate to the acquisition of speech and language and, more generally, to developmental attention and memory for auditory stimuli.     

Neuropsychological functions of hand movements and gestures change in the presence or absence of speech

In order to address previous controversies whether hand movements and gestures are linked to mental concepts or solely to the process of speaking, in the present study we investigate the neuropsychological functions of the entire spectrum of unimanual and bimanual hand movements and gestures when they either accompany speaking or when they act as the only means to communicate in the absence of speech. The results showed that the hand movement activity regarding all types of hand movements and gestures stayed constant with and without speaking. The analysis of the Structure of hand movements showed that executions shifted from in space hand movements with a phase structure during the condition without speech to more irregular on body hand movements without a phase structure during the co-speech condition. The gestural analysis revealed that pantomime gestures increase under conditions without speech whereas emotional motions and subject-oriented actions primarily occur when speaking. The present results provide evidence that the overall hand movement activity does not differ between co-speech conditions and conditions without speech, but that the hands adopt different neuropsychological functions. We conclude that the hands primarily externalise mental concepts in conditions without speaking but that their use shifts to more self-regulation and to endorsing verbal output with emotional connotations when they accompany speech.     

Judgments of synchrony between auditory and moving or still visual stimuli.

The flash-lag effect is a visual illusion wherein intermittently flashed, stationary stimuli seem to trail after a moving visual stimulus despite being flashed synchronously. We tested hypotheses that the flash-lag effect is due to spatial extrapolation, shortened perceptual lags, or accelerated acquisition of moving stimuli, all of which call for an earlier awareness of moving visual stimuli over stationary ones. Participants judged synchrony of a click either to a stationary flash of light or to a series of adjacent flashes that seemingly bounced off or bumped into the edge of the visual display. To be judged synchronous with a stationary flash, audio clicks had to be presented earlier--not later--than clicks that went with events, like a simulated bounce (Experiment 1) or crash (Experiments 2-4), of a moving visual target. Click synchrony to the initial appearance of a moving stimulus was no different than to a flash, but clicks had to be delayed by 30-40 ms to seem synchronous with the final (crash) positions (Experiment 2). The temporal difference was constant over a wide range of motion velocity (Experiment 3). Interrupting the apparent motion by omitting two illumination positions before the last one did not alter subjective synchrony, nor did their occlusion, so the shift in subjective synchrony seems not to be due to brightness contrast (Experiment 4). Click synchrony to the offset of a long duration stationary illumination was also delayed relative to its onset (Experiment 5). Visual stimuli in motion enter awareness no sooner than do stationary flashes, so motion extrapolation, latency difference, and motion acceleration cannot explain the flash-lag effect.