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C Umiltà

Publications and source records attributed to C Umiltà.

At least 73 records · Page 4Linked to original sources
PubMed1983

[Spatial compatibility and position of the effectors].

Mean reaction times obtained with crossed hands (right had on the left and left hand on the right) are slower than reaction times obtained with uncrossed hands (right hand on the right and left hand on the left). These results have been explained as a compatibility effect between the responding hand and its spatial position. The goal of the present experiment was to establish whether the position of the hand is encoded by the subjects relative to their body (absolute position) or relative to the other hand (relative position). The subjects performed a discrimination task on two visual stimuli. Stimuli and hands were either on the same side of the body (both on the left or both on the right) or had different absolute position. In all conditions the subjects responded with crossed and uncrossed hands. The results support the hypothesis that relative position is encoded.

Functional Laterality↗
PubMed1983

[Simon effect and relative position of the stimuli].

The so-called Simon effect can be determined (a) by a natural tendency to respond towards the source of stimulation, or (b) by a comparison between the encoding of the position of the stimulus and the encoding of the position of the effectors producing the response. Twelve subjects performed a manual choice between two visual stimuli in the same visual hemifield. The results of the experiment supported hypothesis (b).

Humans↗
PubMed1983

Do laterality measures relate to speed of response in central vision?

This study was aimed at determining whether an efficiency index (speed of response in central vision) related to a laterality index (difference in speed of response between right and left field presentations). In Experiment 1 female subjects were required to discriminate facial emotional expressions shown in either central vision or the periphery. In Experiment 2 male and female subjects had to classify as same or different pairs of letters printed in different typefaces. It was found that the efficiency index related (negatively) to the laterality index only in Experiment 1 so that slower responses indicate larger visual field differences. The results are discussed in terms of current models of hemispheric specialization.

Discrimination Learning↗
PubMed1983

Hemispheric prevalence in acoustical attention.

Two experiments were conducted in which monaural clicks were presented to the right or left ear preceded by binaural verbal (Experiment 1) and musical (Experiment 2) warnings. After the "neutral" warnings, the clicks could be presented to the right or left ear equally often (50%); after the warnings which directed the attention to the left or right ear, the clicks could be presented to either the "expected" (67%) or to the "unexpected" (33%) ear. In Experiment 1 there was a cost effect for the "unexpected" ear and reaction times were significantly faster when the clicks were presented to the right ear. In Experiment 2, the musical warnings brought about a cost effect while no significant ear advantage was observed.

Acoustic Stimulation↗
PubMed1983

Effects of phonetic similarity and order of report on the right ear advantage.

Two experiments are reported which were aimed at testing the effect of phonetic similarity and order of report on the right ear advantage in consonant-vowel dichotic tasks. The stimuli were consonant-vowel syllables which comprised the six stop consonants: /ba/, /da/, /ga/, /pa/, /ta/ and /ka/. In Experiment 1 the syllables were contrasted on place of articulation (condition 1) or on voicing (condition 2). In Experiment 2 the stimuli were contrasted either on one feature (place or voicing) or on both features (place and voicing). The results showed that the right ear advantage did not depend on phonetic similarity, whereas it depended on the order of report, being stronger when the perceptual channel was considered.

Adult↗
PubMed1982

[Lateralization of attention in the acoustic modality].

Posner reported that knowledge of where in space a visual stimulus will occur ("expected" condition), improves detection ("benefit"), as measured by response latencies, while response latencies became longer ("cost") when visual stimulus position is "unexpected" and intermediate when the visual stimulus position is "neutral". The authors have tried to replicate this finding in the acoustical modality. One hundred-twenty acoustical stimuli (clicks) were presented to the right and the left ear of ten right handed subjects, preceded by the biaural verbal warnings "right", "left" or "center". After the "center" verbal warning, the clicks could be presented to the right or the left ear equally often (50%): "neutral" condition; after the "right" or "left" verbal warnings, the clicks could be presented in 80% of cases to the "expected" ear and in 20% of cases in "unexpected" ear. The results suggested that: a) reaction times are significantly faster when the clicks are presented to the right ear; b) the "cost" effect is present but not the "benefit" effect, since no difference was shown between reaction times in the "neutral" and in the "expected" conditions; c) the right ear advantage disappears in the "unexpected" condition after the "right" verbal warning only. The authors discuss the results in relation to the attentional interhemispheric theories.

Acoustic Stimulation↗
PubMed1982

Functional cerebral lateralisation; dichotomy or plurality?

Cartoon faces were presented tachistoscopically in the right and left visual fields, and required to be matched to a previously memorised target face. The three different stimuli differed from the target either on only one, or on all three features (eyes, nose, mouth). Reaction times varied considerably across the individual different responses in both conditions. In the first condition field differences consistently favoured the right field; in the second, two favoured the left and the third the right. In both conditions same responses were faster than at least one different response class. Several interpretations in terms of the distinction between "analytic" and "holistic" processes were entertained. Such processes themselves remain somewhat obscure, but there is nothing in the data to suggest that the two cerebral hemispheres might not be essentially ambivalent in their predilections for the two kinds of processing. In which case future research might profitably focus on the emerging plurality of experimental factors governing this cognitive ambivalence, rather than on the simple physical dichotomy.

Adult↗
PubMed1982

Can an analytic/holistic dichotomy explain hemispheric asymmetries?

Same RTs to pairs of letters or other patterns are often faster than different RTs. This finding has led to hypothesize a two-process system of comparison: a fast holistic process for same and a slower analytic process for different responses. In connection with hemispheric specialization, RH has been characterized as a holistic and LH as an analytic processor. Therefore same responses should be mediated by RH and different responses by LH. In the present study, subjects made same-different judgments in the two visual fields to successively presented pairs of letters where degree of difference was systematically varied. RTs decreased with increases in the degree of difference in different responses. Same responses were faster than different. These results suggest analytic processing of different and holistic processing of same pairs. Since no clear-cut visual field superiority was found, the conclusion is that both hemispheres can process visual information analytically and holistically.

Adult↗
PubMed1982

Spatial compatibility effects on the same side of the body midline.

Stimulus-response compatibility effects have been hypothesized to result (a) from a subject's innate tendency to respond in the direction of the source of stimulation, (b) from a correspondence between the spatial codes associated with the effector and the stimulus, or (c) from an attentional bias favoring the effector located in the same hemispace as the command signal. Two experiments were conducted to test these three hypotheses. In Experiment 1 the subjects were requested to make unimanual discriminative key-pressing responses to two light stimuli, both appearing to either the right or left of the fixation point. In one condition the two hands were in anatomical position (uncrossed); in the other they were crossed. The procedure of Experiment 2 was similar to that of Experiment 1 with the exception that both hands, always in an uncrossed position, were placed on the same side of the body midline (on the right or left). The results showed that the compatibility effect depends on a correspondence between the spatial codes associated with the location of the effector and the location of the command stimulus.

Adult↗
PubMed1980

[Reaction time experiment on absolute or relative functional specialization of the cerebral hemispheres in man].

Lateralized presentations of verbal stimuli yield faster reaction times in the right visual field-left hemisphere, whereas nonverbal stimuli yield faster reaction times in the left visual field-right hemisphere. However, the problem of how lateral asymmetries in response latency are determined is still unsolved. The hypothesis of an absolute functional specialization of the two hemispheres suggests that information presented in the visual field connected with the unspecialized hemisphere has to travel along a less direct pathway, implying a crossing through the forebrain commissures, to reach the processing center. The hypothesis of a relative functional specialization assumes that stimuli are processed by the hemisphere contralateral to the field of presentation but speed of processing varies as a function of hemispheric specialization. The present study tried to find empirical evidence in favor of one of the two hypotheses. Choice reaction times to lateralized verbal stimuli were studied in normal subjects. In half of the trials the subjects had to carry out a concomitant task known to interfere selectively with mechanisms responsible of the organization of the responses of the left hemisphere. Both with and without concomitant task reaction times were significantly faster in the right visual field-left hemisphere. While the concomitant task produced an overall lengthening of reaction time, it did not affect interhemispheric asymmetry. This finding was discussed as evidence in favor of the absolute specialization hypothesis.

Acoustic Stimulation↗
PubMed1980

[Spatial stimulus-response compatibility: presentation of stimuli within one visual hemifield].

Choice reaction times of two lateralized unstructured visual stimuli located within the same (right or left) visual hemifield were studied in subjects with hands crossed and uncrossed. The subjects were instructed to respond with their right or left hand depending on the position of the stimulus. In one experimental condition they have to use their right hand for responding to the right light and their left hand for responding to the left light. In another experimental condition the reverse arrangement was used. The two light stimuli were presented, one at a time and 3 degrees apart, in both visual fields. Thus, the analyzed factors were: hand position (crossed or uncrossed), responding hand (right or left), field of presentation (right or left), and relative position of the light stimulus (right or left). The main finding of the present study was that spatial compatibility effects were present even when both stimuli were presented within the same visual field. That means that the factor determining which hand is faster in responding is the relative position of the two stimuli and of the two hands and not the position of the stimuli with reference to the vertical meridian.

Functional Laterality↗
PubMed1980

Laterality effects, levels of processing, and stimulus properties.

Two hypotheses of hemispheric specialization are discussed. The first stresses the importance of the kind of processing to which the stimulus is subjected, and the second stresses the importance of the nature of the stimulus. To test these hypotheses, four experiments were carried out. In Experiment 1 verbal material was employed in a same-different classification task, and an overall right visual field superiority was found. Experiment 2, in which verbal stimuli were subjected to visuospatial transformations (i.e. mental rotations), yielded no laterality effect. In Experiment 3 geometrical figures were employed in a classification task similar to that of Experiment 1, and an overall left visual field superiority was found. In Experiment 4 both verbal and geometric stimuli were employed. The results showed a significant interaction between field of presentation and nature of the stimulus and no interaction between field of presentation and level of processing.

Discrimination Learning↗