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C Umiltà

Publications and source records attributed to C Umiltà.

At least 55 records · Page 3Linked to original sources
PubMed1992

[Facilitating and inhibiting effects of the orientation of attention using peripheral cues].

The attentional field resulting from the presentation of peripheral cues; which were either informative or non informative about the position of the imperative stimulus, was studied. Different time intervals between cue and stimulus (120, 300, 600 ms) were used. The results showed facilitation of the response with the informative cue and inhibition with the non informative cue. This happened for the longest cue-stimulus intervals and when the position of the cue and the position of the stimulus were congruent. Also order of cue presentation (i.e., either informative followed by the non informative cue or vice versa) proved important in producing facilitatory and inhibitory effects.

Attention↗
PubMed1991

Influence of different types of grasping on the transport component of prehension movements.

The main aim of the present study was to clarify whether different types of grasping may affect the transport component of prehension movements. To this purpose two experiments were carried out. In the first experiment the kinematics of arm movements (transport and manipulation components) were studied in eight normal subjects instructed to reach and grasp different objects located either 20 or 30 cm from their hand. The objects employed required two different types of grip: prehension with the whole hand and prehension with the index finger and the thumb (precision grip). In the second experiment subjects were instructed to point to the same objects employed in the first experiment. This experiment served as a control for the precision requirements related to the object size. The results showed that, once the precision requirements were taken into account, the transport component remained unmodified with the different types of grip. The time course of the manipulation component and its temporal relations with the transport component changed with the type of grasping. The maximal hand aperture was reached earlier in the precision grip than in the whole hand prehension and the temporal coupling with the transport component was weaker in the former condition than in the latter. The data are interpreted as further evidence in favour of independence between the transport and the manipulation "channels".

Adolescent↗
PubMed1991

[Orientation of attention in the visual space].

The display was composed of four boxes, horizontally aligned above the fixation point. In Experiment I, each box was cued by a digit shown at fixation. In Experiment II there were only two numeric cues, signalling the inner or the outer boxes, depending on the experimental condition. The subject was instructed to orient attention to the cued box, and to respond to the imperative stimulus as fast as possible, wherever it appeared. By using four time interval (SOAs), we tried to determine the route covered by attention movements. In Experiment I, with the shortest SOA (100 msec), it was shown that attention does not reach the cued box through a direct path. Rather it moves first on the inner boxes, thereafter focusing on the cued location. The same results were obtained in Experiment II, where the cue directed attention to the inner boxes. When the external boxes were cued, however, this trend was not observed.

Adult↗
PubMed1991

[Orientation strategy implicit in spatial attention].

In this experiment, two rows of four boxes, one above and the other below the fixation point, were displayed on a computer monitor. A cognitive numeric cue indicated one of the four external boxes, where the attention was to be directed. Stimuli, however, could occur in any of the eight boxes. The subject was instructed to respond to the imperative stimulus as fast as possible, regardless of its location. Four time intervals between cue and stimulus presentation (SOAs) were employed in order to disclose the route along which attention is moved. With the shortest SOA (100 msec) an indication that attention movements follow the cartesian/orthogonal axes was shown.

Adult↗
PubMed1990

Size of the attentional focus and efficiency of processing.

By following Eriksen and St. James (1986) the experiments reported in this study focused upon three questions: (a) Can the spatial extent of the attentional focus be made to vary in response to precues? (b) As the area of the attentional focus increases, is there a decrease in processing efficiency for stimuli within the focus? (c) Is the boundary of the focus sharply demarked from the residual field or does it show a gradual dropoff? The results seem to provide answers to these questions: (a) the size of the attentional focus can be adjusted so that it covers areas of the visual field of different size; (b) there is a decrease in processing efficiency when the area of the attentional focus increases; and (c) there is a gradual dropoff in processing efficiency around the attentional focus.

Adult↗
PubMed1990

The deployment of visual attention in the intact field of hemineglect patients.

Patients with left hemispatial neglect after right hemisphere lesions and control patients with right hemisphere lesions were presented in the ipsilesional (i.e., intact) visual field with stimuli that could occupy left-right relative positions. The patients were required to discriminate between target stimuli and distractors by emitting go/no-go responses. Reaction times (RTs) and measures of sensitivity (d') and response bias (beta) were obtained. The within-subjects comparisons showed that neglect patients were faster in the right than the left relative position, whereas control patients were faster in the left than the right relative position. The between-subjects comparisons showed that neglect patients were faster than control patients in the right relative position but slower in the left relative position. These effects were due to changes in processing efficiency, as attested by the fact that the differences in response speed were accompanied by congruent differences in sensitivity, whereas no differences in response bias were found. The results were interpreted by assuming that neglect patients focus attention on the right relative position and, therefore, have a small attentional focus concentrated on that position. By contrast, control patients, like normal subjects, would distribute attention between the two possible stimulus positions and, therefore, allocate attention to a larger portion of the visual field.

Analysis of Variance↗
PubMed1990

Is there a modality effect? Evidence for visual recency and suffix effects.

In Experiment 1, four groups of 16 subjects performed ordered recall of six-syllable lists in both suffix and nonsuffix conditions. Sequential presentation of the lists varied for each group. In the auditory presentation, the syllables were delivered from one location only and were read aloud by the subjects. For the visual, spatially nondistributed presentation, the syllables appeared in one location only and were read silently. For visual, spatially distributed presentations, the syllables were spread out either vertically or horizontally and were read silently. Very robust recency and suffix effects were found in the auditory presentation, as well as in visual, spatially distributed presentations. In Experiment 2, 16 subjects performed ordered recall of visually presented lists with the items spread out vertically and conflicting spatial and temporal orders. A reliable recency effect was found for the final block of trials. In Experiment 3, 16 subjects performed ordered recall in the same conditions as in Experiment 2, except that they were instructed to recall the temporal order in which the spatial positions would be filled in. A bow-shaped curve and a strong recency effect were obtained.

Adult↗
PubMed1989

Multiple mechanisms for recency with vowels and consonants.

Three experiments were conducted to test the hypothesis that the difference in recency effect between vowel-contrasting and stop-contrasting lists of syllables in immediate ordered recall can be explained by item discriminability and regular short-term memory mechanisms, without any recourse to echoic memory or precategorical acoustic storage (PAS). In Experiment 1, the short-term memory mechanisms were manipulated by reducing amount of output interference and length of retention interval. The partial-report technique was used. The most important finding was the usual final-position recency effect (difference in recall between the fifth and sixth serial positions) for the vowel lists but not for the stop lists, regardless of the type of report. Thus the PAS theory could not be rejected. In Experiments 2 and 3, the last item was differentiated from the other items of the list, either by lengthening the interstimulus interval between the last and the next-to-last (Experiment 2) or by increasing the intensity of the last item (Experiment 3). In both cases, an increase of the final-position recency effect was found even for stop lists. Since a drop in recall errors was also obtained for the fourth item when its intensity was increased (von Restorff effect), this final-position recency effect for stop lists is likely to be due to item discriminability, and not to echoic memory for the last item. Item discriminability appeared to be the critical factor.

Discrimination, Psychological↗
PubMed1989

[Kinematic study of reaching-grasping movements].

The experiment was conducted to investigate, by using kinematic parameters, the influence of the type of prehension on the transportation component in reaching-grasping movements. The main question was whether the transportation component is influenced by the type of prehension besides the distance of the object. The experiment was carried out on eight subjects who performed reaching-grasping movements toward objects located at different distances. Two types of prehension were examined: whole hand prehension and precision grip. The following kinematic parameters of the transportation component (wrist movement) were studied: movement times, profiles of velocity and accelerations. Our results have shown that the transportation component is affected by the two factors. However the kinematic parameters were influenced differently by the distance and the type of prehension. Our conclusion is that, although distance and type of prehension affect the transportation component, they are computed separately in programming this component.

Adolescent↗
PubMed1989

[Effects of age on orientation of attention].

The present experiment investigated the influence of age on the magnitude of attentional effects. Subjects were cued to attend to one of two possible stimulus locations horizontally arranged. The instructions were to respond as fast as possible to the occurrence of a visual stimulus, regardless of whether it occurred in a cued or in a non-cued location. When the stimulus occurred in a non-cued location, the subject had to reorient attention to the non-attended, but stimulated, location. Reorienting of attention was directed toward either the left or the right side. The results showed that for the elders, time for reorienting was longer than for younger subjects.

Adult↗
PubMed1985

Familiarity, spatial frequency and task determinants in processing laterally presented representations of faces.

Laterally presented portraits were judged as familiar or unfamiliar (Experiments 1 and 2), or were processed in a target matching task (Experiment 3). Exposure durations (100 or 190 msec.) were varied between (Experiments 1 and 2) or within (Experiment 3) the experiments. Clear and degraded faces appeared either randomly intermingled (Experiment 1) or in blocked sequences (Experiments 2 and 3). In Experiment 3 familiar and unfamiliar stimuli also appeared in blocks. Stimulus degradation was achieved by coarse quantization of the image into blocks, so replacing relevant high-spatial-frequencies (the features) by spurious information, preserving only the original lower-spatial-frequency components. Left hemisphere mediation was strongest and most consistent with long exposures and random sequences of clear and degraded stimuli. Right hemisphere mediation tended to appear with shorter exposures and degraded stimuli presented in blocks. Though the interactions were often complex, the general pattern of results was consistent with the analytic-holistic processing dichotomy.

Discrimination Learning↗