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Biomedical subjects

I Rock

Publications and source records attributed to I Rock.

At least 37 records · Page 2Linked to original sources
PubMed1988

Size constancy in children: a new interpretation.

Existing evidence indicates that there are differences between children and adults in size constancy when observation distances are large. Findings are reported which suggest that this phenomenon is based on a difference in the accessing of proximal stimulus information, which, in the case of size, refers to visual angle subtended. Age differences were found when a traditional size constancy task was used, but these differences disappeared when all the comparison objects subtended the same visual angle. Since this finding demonstrates that young children can make accurate size matches, it is suggested that the underconstancy previously reported is not necessarily the result of children's inability to use fully certain cues to distance. Rather, the findings suggest that children access proximal stimulus information more spontaneously than do adults.

Adolescent↗
PubMed1987

Eye movement as a cue to figure motion in anorthoscopic perception.

When a figure moves behind a narrow aperture in an opaque surface, if it is perceived as a figure, its shape will often appear distorted. Under such anorthoscopic conditions, the speed or direction of the object's motion is ambiguous. However, when the observer simultaneously tracks a moving target, a figure is always perceived, and its precise shape is a function of the speed or direction of tracking. The figure is seen as moving with the speed or in the direction of the target. Thus, it is argued that eye movement serves as a cue to the figure's motion, which, in turn, determines its perceived length or orientation.

Cues↗
PubMed1986

The optomotor response and induced motion of the self.

Although the optomotor response in animals and induced motion of the self in humans occur under very similar stimulus conditions, they have not hitherto been related. Experiments with fish are reported which support the hypothesis that the optomotor response is based on the animal's attempt to nullify the unwanted experience of its own motion that is imposed upon it.

Animals↗
PubMed1983

Illusory contour lightness: a neglected possibility.

When the area occupied by a typical sharp-edged illusory figure is outlined physically, some illusory lightness survives within the contours as an example of figure-ground contrast. This general phenomenon may therefore account for the direction of the apparent alteration in lightness found within many illusory figures, but it cannot account for the magnitude of that alteration.

Form Perception↗
PubMed1983

Maternal and fetal effects of prophylactic hydration with crystalloids or colloids before epidural anesthesia.

Prophylactic intravenous hydration decreases the incidence and severity of hypotension due to obstetric epidural anesthesia. This study assesses whether infusion of normal serum albumin (NSA) offers any advantages over Ringer's lactate (RL) solution. Sixty patients scheduled for elective cesarean sections were divided into three equal groups. Group 1 received 1200 ml of RL; group 2, 700 ml of RL plus 500 ml of 5% NSA; and group 3, 1000 ml of RL plus 200 ml of 25% NSA. In group 1, the concentrations of serum albumin (SA) decreased from 3.5 +/- 0.3 (mean +/- SD) to 3 +/- 0.2 g/dL (P less than 0.01) and plasma oncotic pressure (POP) from 20 +/- 3 to 17 +/- 3 torr (P less than 0.005) immediately after hydration. In group 2, SA remained unchanged, but POP decreased from 21 +/- 2 to 19 +/- 2 torr (P less than 0.005). In group 3, SA increased from 3.6 +/- 0.5 to 3.9 +/- 0.3 g/dL (P less than 0.01) and POP from 19 +/- 2 to 21 +/- 2 torr (P less than 0.0025). Neither SA nor POP levels differed among the groups 24 h later; however, both SA and POP were significantly lower than preinfusion values in all groups at 24 h. The incidence of maternal hypotension, neonatal Apgar scores, and acid-base status also were comparable among the groups (X2 analysis). Because low POP may predispose to postoperative pulmonary morbidity, the incidence of this complication was studied in the mothers by using a point scoring system (based on the presence of symptoms and physical signs) and also by measuring AaDO2 gradients. Neither pulmonary morbidity scores nor AaDO2 gradients differed significantly in the three groups. It is concluded that both crystalloid and colloid prehydration produce equally satisfactory maternal and fetal outcomes.

Adult↗
PubMed1982

The rod-and-frame effect as a function of the righting of the frame.

Several experiments investigated the theory that there is a tendency to interpret the axes of a large tilted frame of reference as surrogates of the main axes of the environment. Therefore there is a tendency to perceive such a frame as either upright or as less tilted thanit is--righting-- and, accordingly, to perceive a vertical rod as tilted in the opposite direction--the rod-and-frame effect (RFE). A high correlation was found between righting and the RFE in all experiments. When a double frame apparatus was used, with the outer frame upright and the inner frame tilted, there was no consistent RFE. This condition eliminates any righting effect. When the outer frame was tilted and the inner one was upright, however, the RFE was induced, as was a correlated righting effect. All experiments were repeated with the subject's head tilted, thereby increasing the tendency toward righting of the frame. The result was a corresponding increase in the RFE. The RFE can thus be thought of as the solution to the problem of the rod's tilt given the perceived tilt of the frame.U

Discrimination Learning↗
PubMed1982

The construction of a plane from pictorial information.

Experiments are described which support the theory that the perception of a plane receding in depth is based on a process of construction. Displays were created which eliminated direct or higher-order stimulus information concerning the orientation of a plane, such as texture gradients or perspective. Instead, objects and the shadows they cast sufficed to suggest and support a depth interpretation. The perceived location of objects on this constructed plane affects size perception thereby providing evidence for a computational rather than a direct theory of constancy.

Cues↗
PubMed1981

Alternative solutions to kinetic stimulus transformations.

It has been assumed that certain stimulus transformations lead directly to depth effects, that is, that such transformations are the necessary and sufficient conditions for kinetically generated depth perception. An alternative is to view such perception as the preferred solution to the problem posed by the transforming stimulus as to what even in the world is producing that transformation. In several experiments it is shown that when other solutions are supportable by the stimulus, those same transformations will no longer lead to depth perception. These other solutions become preferred on the basis of rejection of certain coincidental features of the stimulus that otherwise would have to be accepted were the kinetic depth solution to be maintained. The findings are interpreted as challenging any theory that perception is simply the direct result of stimulation or of extraction of stimulus information and as supporting the Helmkoltzian rule of perception as a construction of the most reasonable representation.

Depth Perception↗
PubMed1981

The effect of inattention on form perception.

A state of inattention was achieved by having subjects selectively attend to one of two overlapping novel figures in a series of such overlapping figures. Recognition of form directly afterward was good for figures that had been attended to but was essentially nil for the unattended figures. Recognition failed to occur even if a familiar figure was in the unattended series and even if that figure was presented 1 sec before the test. A further experiment showed that certain general characteristics of the unattended figures other than form were recognized. The results are interpreted as indicating that attention is necessary for form perception, not merely for memory of form. It is suggested that a cognitive process of description constitutes the essence of form perception. Diverting attention eliminates the cognitive operation of describing the spatial relations that characterize a figure.

Attention↗
PubMed1981

The effect on form perception of change of orientation in the third dimension.

The experiments reported here concern the effect of change of orientation of figures in the third dimension on phenomenal shape. In one experiment, novel two-dimensional wire figures were first shown in one orientation in the sagittal plane, and recognition of them was then tested in an altered orientation in that plane. In another experiment, novel three-dimensional wire figures were first shown in one orientation, and recognition of them was tested following rotation about one of the three major axes of space. The guiding hypotheses were (a) form perception is the end result of a process of figural description; (b) orientation change that alters the perceived location of the top, bottom, and sides of a figure will affect this description; and (c) front-back reversal and rotations about the Y axis will not affect the description because front and back constitute the sides of a figure much as left and right do, and all figural sides are phenomenally equivalent. The findings support these hypotheses except for an unanticipated effect on recognition of 90 degrees rotations about the Y axis. This effect was seen as a hitherto unknown example of egocentrism in perception, since the description is governed by the retinal projection resulting from the particular vantage point of the observer.

Depth Perception↗
PubMed1980

Induced movement based on subtraction of motion from the inducing object.

Induced movement occurs not only when an object surrounding a stationary one moves below threshold but when it moves above threshold. The above-threshold effect is particularly puzzling and seemingly irrational because the relative displacement should be fully accounted for by perceiving the moving object in motion. The accepted theory has been that such excess motion can be explained in terms of a separation of systems: The enclosed object is governed by the relationship to its immediately surrounding frame of reference, and the latter is governed either by the relationship to its surrounding frame of reference or to the observer. An alternative explanation is that when induced motion occurs, the moving object is perceived to be either stationary or moving less than is warranted by its actual motion. Evidence is presented supporting this hypothesis according to which the relative displacement is apportioned phenomenally to either the induced object, the inducing object, or both. The objective motion of the inducing object is thus in whole or part transferred to the induced object. Thus, excess phenomenal motion does not occur, and induced movement can be regarded as the rational solution to a problem.

Form Perception↗
PubMed1979

Illusory contours as the solution to a problem.

The perception of certain figures with illusory contours entails a reversal of figure and ground. It is hypothesized that this process occurs in two stages. First, some factor must suggest or cue the reversal. Experiments are described that isolate three such factors, namely, alignment of physically present contours, recognized incompletion of parts of the stimulus array, and set. Once cued, however, other experiments indicate that in a further stage of processing the solution is examined with respect to its compatibility with the stimulus display or with other preceptual properties to which the display gives rise. Only if such compatibility is present will the perception of a figure with illusory contours be maintained.

Cues↗
PubMed1978

Pictorial depth and related constancy effects as a function of recognition.

It is argued that while pictorial cues must be fundamental in the perception of an extended ground plane in daily life (and, by definition, in the perception of depth in pictures), the traditional pictorial cues such as perspective or texture gradients are neither a necessary nor a sufficient basis for it. That they are not necessary was shown by experiments in which such cues were eliminated from pictures representing a scene in depth. Illusory size perception based on localization of objects in depth in such pictures nonetheless occurred. That they are not sufficient was shown by experiments in which photographs of grassy fields did not yield impressions of depth or related size illusions when conditions were such that the scene was not recognized. Once recognized, however, these same pictures did yield such perceptions. It is suggested that a critical step in perceiving depth based on pictorial information is recognition of the scene.

Art↗