Biomedical subjects

F Giusberti

Publications and source records attributed to F Giusberti.

3 recordsLinked to original sources

PubMed1998

Moving around objects and recognizing them.

This research concerned the use of mental rotation in recognizing rotated objects. Instead of the classic Shepard's paradigm in which subjects were still while observing rotated objects, here subjects had to move (or imagine moving) around stationary three-dimensional objects put in the middle of the trajectory. Thus, depending on the viewing positions, such objects were seen under six different perspectives (from 30 degrees to 180 degrees). The latter task has been thought to be closer to everyday life in which we obtain information regarding objects from their spatial properties. The results do not follow the classic rules of mental rotation of an object predicting a linear increase of the time needed to recognize distorted objects as a function of their angular displacement. They also differ from data in the literature about spatial imagery showing that access to spatial information is facilitated more when people actually move through a path than when they imagine moving. A probable explanation of this difference from the literature is discussed in relation to the particular involvement of the body in the experimental task.

Adult↗

PubMed1996

Metric aspects of mental images.

This research concerns the representation of size and shape in long-term memory at different levels of abstraction. Some authors suggested a distinction between surface characteristics, including size, depending on an observer's point of view (viewer-centered), and abstract characteristic based only on an object's shape (object-centered). These studies raise the question of whether size-information is stored in long-term memory. This question may be dealt with by considering the topic of cognitive costs; since abstract representation needs more processing, more time is required to store fewer abstract representations than many viewer-level representations. Two hypotheses were put forward: information about size is preserved when an intermediate time is allowed to process visual stimuli, whereas it is discarded when a longer time is available; subjects who have longer time focus on shape, while subjects who have less time do not. Subjects were assigned to two groups differing in the time allowed to learn visual images. Both groups had to recognize previously learned visual mental images. These images were built up by a subtraction task. The testing stimuli were identical to learned ones, of a different size, or of a different shape. Analysis showed that information about size is not held in long-term memory. As regards shape, results were controversial.

Adult↗

PubMed1992

Differences in vividness ratings of perceived and imagined patterns.

The present research focuses on the different subjective experiences evoked by perceived and imagined matrices of letters of the alphabet. In three experiments adult subjects were asked to rate the vividness of a letter included in a matrix of letters which varied due to manipulations in colour, rotation and movement. Subjects were asked to observe (perceptual modality), draw and observe (drawing modality), retrieve (memory modality) or imagine (imagery modality) the matrices. For some manipulations of the critical letter (in particular, 45 degrees inclination and high contrast colour), the perceptual modality produced comparatively higher vividness ratings than the other two modalities. The perceptual effect of inclination was also duplicated with the memory modality group. It is argued that different visual processes, either immediate and pre-attentive, or sequential and attentive, may be operating under voluntary control. Although visual imagery varies in some ways from immediate visual perception, the similarities found, between the drawing and imagery modalities, on the one hand, and the perceptual and memory modalities, on the other hand, suggest that they share some common underlying processes.

Adult↗