Physiological response and task performance in like- and cross-sex competition

The relationship between a subject's sex and his or her behavior in a competitive situation was examined. Male and female subjects completed three tasks, first by themselves and then against either a male or female competitor. A 2×2 design (sex of the subject × sex of the competitor) was thereby created. The dependent measures were the subject's performance and his or her heart rate during each task. Since the relationship between a subject's sex and competitive behavior was expected to be situationally specific, three different kinds of tasks were used: anagram, perceptual-motor, and arithmetical. Results were not consistent with predictions based on Horner's fear of success model (1968). Competition with either sex was found to increase performance level in both sexes on all three tasks. The only sex-related effect found to be consistent across tasks was that both male and female subjects had a greater increase in heart rate when competing against a male than when competing against a female. This heart rate increase was interpreted as an indicator of increased anxiety or arousal.This research was supported by a University of Pittsburgh, Faculty of Arts and Sciences research grant to the second author. The assistance of H. DeGood, L. Paul, and T. Rusiewicz in collection of the data presented here is gratefully acknowledged.     

Perception of the head transversal plane and the subjective horizontal during gondola centrifugation

The subjective visual horizontal (SVH) and the subjective head transversal plane (STP) were measured by means of an adjustable luminous line in darkness during centrifuging. Subjects (N = 10) were seated upright, facing forward in a swing-out gondola. After acceleration of the centrifuge to 2G (vectorial sum of the earth's gravity and the centrifugal force; gondola inclination 60 degrees), subjects had to set the line either so that it was perceived as gravitoinertially horizontal (SVH) or so that it was perceived as parallel with the transversal ("horizontal") plane of the head (STP). Initially after acceleration, the SVH was tilted with respect to the gravitoinertial horizontal of the gondola (M = 16.6 degrees). This tilt was compensatory with respect to the gondola inclination. However, the STP was tilted in the opposite direction (M = 12.4 degrees), which might suggest a vestibular-induced distortion of the mental representation of one's own body. Similar results were obtained when measuring the subjective visual vertical (SVV) and the subjective midsagittal plane (SSP) in 5 subjects. The perceived roll angle (obtained as SVH-STP or SVV-SSP) was considerably larger than had previously been reported. Time constants for exponential decay of the tilt of the SVH or SVV were often 2-3 min, indicating a memory for semicircular canal information on changes in head orientation--a position-storage mechanism.     

The assessment of subjective visual vertical: comparison of two psychophysical paradigms and age-related performance

Perception of the subjective visual vertical (SVV) is usually assessed by asking to subjects, in complete darkness, to adjust the position of a luminous rod that is variably tilted (i.e., by the method of adjustment [ADJ]). Conversely, the two-alternative forced choice (2AFC) method requires subjects to categorize, as tilted either clockwise (CW) or counterclockwise (CCW), stimuli that are presented on a computer screen and are variably tilted from vertical. In this study, we aimed to compare the results of these two methods and investigate age-related effects on the SVV. SVV was assessed in 102 healthy individuals, 50 women and 52 men, with a mean age of 45.7 (range 20–91), using both ADJ (ten trials, initial 1°, 2°, 4°, 8°, or 12° bar tilts both CW and CCW) and 2AFC (120 stimuli with a 1°–32° variable tilt). Also, 50 of the subjects performed the ADJ test twice, with different bar lengths. We estimated bias and threshold for the two methods, and found that neither measure differed across the methods. Age was a significant predictor of threshold (2AFC, R ² = .141; ADJ, R ² = .190; p < .001), implying lower sensitivity with increasing age. Moreover, the ADJ method showed a significant increase of bias when the initial tilt was farthest from vertical, whereas the rod length was irrelevant. SVV measures obtained with the ADJ and 2AFC methods were comparable, but the latter measures were more resistant to artifacts that might affect the measurement. The lower sensitivity found in older persons may have an influence on their ability to interact with the environment and may contribute to impairment of postural control.     

Contribution of somesthetic cues to the perception of body orientation and subjective visual vertical

Without relevant visual cues, the subjective visual vertical (SVV) is biased in roll-tilted subjects toward the body axis (Aubert or A-effect). This study focused on the role of the somatosensory system with respect to the SVV and on whether somesthetic cues act through the estimated body tilt. The body cast technology was used to obtain a diffuse tactile stimulation. An increased A-effect was expected because of a greater underestimation of the body position in the body cast. Sixteen subjects placed in a tilt chair were rolled sideways from 0 degrees to 105 degrees. They were asked to verbally indicate their subjective body position and then to adjust a luminous line to the vertical under strapped and body cast conditions. Results showed a greater A-effect (p < .001) but an overestimation of the body orientation (p < .01) in the body cast condition for the higher tilt values (beyond 60 degrees). Since the otolith organs produced the same gravity response in both conditions, errors were due to a change in somesthetic cues. Visual and postural errors were not directly related (no correlation). However, the angular distance between the apparent body position and the SW remained stable, suggesting that the change in somatosensory pattern inputs has a similar impact on the cognitive processes involved in assessing the perception of external space and the sense of self-position.     

Torso movement constraint in stability of bimanual coordination

This study investigated the relation between postural movement and upper-limb coordination stability. Adults produced bimanual circles using in-phase and anti-phase coordination patterns in time to an increasing rate metronome (i.e., movement-time instruction) in the horizontal (e.g., tabletop) and vertical (e.g., "wall" perpendicular to body) planes. All participants produced the instructed in- and anti-phase patterns. Coordination stability (i.e., SD of relative phase) was larger for anti-phase than in-phase patterns in both planes; however, anti-phase coordination stability was lower in the vertical plane than in the horizontal plane. Torso movement was larger during anti-phase coordination patterns in the horizontal plane, whereas it was larger during in-phase coordination patterns in the vertical plane. These results indicate that different orientations of the same task can produce different results for stability of coordination. This information may be important for performing and learning complex motor-coordination movements (e.g., playing musical instruments).     

Imagined body orientation and perception of the visual vertical

The existence of body orientation mental imagery was tested by examining whether self roll tilt imagery affects the subjective visual vertical (SVV). Twenty healthy subjects judged the orientation of a dim luminous bar with respect to gravitational vertical, while normally seated in complete darkness with their head firmly restrained earth vertically. SVV was measured in three conditions: a reference condition with no imagery, and a left and a right imagery condition, during which the bar orientation was to be judged while the subjects imagine themselves roll-tilted towards left or right, respectively. The imagined roll tilts were of the same magnitude as roll tilts which generally induce an E- effect, i.e., an SVV lean toward the side opposite to those of body tilt. If imagery and perception of self roll tilt share common processes, self roll tilt imagery should induce an E-like effect. Results show an imagery- induced E-like effect, which strongly supports the idea that humans can perform mental imagery of body orientation about gravity. Received: 4 April 2000 / Accepted: 1 September 2000     

The influence of the acoustic context on vertical sound localization in the median plane

The influence of background sounds (frames) on vertical localization of single sound sources (targets) was examined in four experiments. Loudspeakers (five targets and four frames) were positioned in the median plane, ranging from +30 degrees to -30 degrees above and below the subject's ear level. The subjects determined the vertical position of the targets by either verbal judgments or manual pointing. Frame and target sounds were presented concurrently or successively with a 1-sec interval; both consisted of (1) 300-Hz square waves, (2) noise, or (3) targets of noise and frames of 300-Hz square waves. Particularly in the second condition, the subjects consistently shifted the apparent target positions away from the frame locations. This contrast effect persisted even 1 sec after the offset of the frames. No effect was found with different waveforms for the frame and the target. Results are related to recent findings indicating a similar effect in the azimuthal dimension. Possibly the effect is based on a mechanism in which the auditory system adapts to recently heard sound source positions.     

External loading and maximum dynamic output in vertical jumping: the role of training history

We examined the effect of training history on the load-power relationship in vertical jumping (VJ) by employing external loads ranging from -30% to +30% body weight (BW). Based on previous findings, we hypothesized that (1) the maximum dynamic output (power production and momentum generation) would be within the tested loading interval, and (2) the load-power and load-momentum relations would depend on the subject's training history. Thirty-one healthy male subjects of different training history (i.e., 9 strength-trained athletes, 12 speed-trained athletes, and 10 sedentary individuals), performed maximum countermovement jumps on a force plate while a pulley system was used to either reduce or increase the subject's BW. An increase in external loading during VJ resulted in a systematic decrease (p<.001) in power production and momentum generation in all 3 studied groups. We also observed significant Group×Load interactions (p<.01) for the load-power and the load-momentum relationships, probably due to the group differences in slopes of the trend lines that describe the loading-associated changes in power and momentum. The results suggest that, from the evolutionary standpoint, the human muscular system of the lower limbs could be designed to produce the maximum power output against the loads that are well below the mass and inertia of the human body.     

Limiting the recruitment of degrees of freedom reduces the stability of perception-action patterns

The goal of the present study was to examine how recruiting/suppressing degrees of freedom affects the (differential) stability of two rhythmic perception-action patterns. In particular, participants synchronized either adduction-on-the-beat or abduction-on-the-beat movements of the right index finger with an auditory metronome. The stability of both patterns as performed in the horizontal plane was predicted to depend on the utilization, or recruitment, of the vertical plane of motion. Movements of the index finger were either free or physically restricted to the horizontal plane. The results showed that in the free condition, the vertical plane was recruited more in the more stable pattern (abduction-on-the-beat) than in the less stable pattern (adduction-on-the-beat). In the constrained condition, abduction-on-the-beat pattern was destabilized, whereas the stability of the adduction-on-the-beat pattern was preserved. These results suggest that the recruitment of the vertical plane of motion in the abduction-on-the-beat movements brought about an increase in the stability of this pattern. More generally, the trade-off between the stability of coordination patterns in the horizontal plane is based on a self-organizing process of recruitment in which neuromuscular factors are an intrinsic aspect.     

Spatial coding and oblique discrimination by children

Children from five to eight years of age learned to discriminate between mirrorimage oblique lines more readily when cards bearing the obliques were presented vertically than when they were presented horizontally. The difference in performance between the vertical and horizontal planes could not be accounted for by differences in either the external visual context or the availability of asymmetrical body information (e.g., left vs right hand). The superiority of the vertical plane was attributed to the congruence of objective, bodily, and retinal vertical axes for the vertical, but not the horizontal plane, It was concluded, on this basis, that at least part of children's difficulty discriminating between mirror-image obliques is due to their difficulty establishing the internalized vertical axis necessary for the left-right spatial coding of the obliques.     

Human motor responses to simultaneous aversive stimulation and failure on a valued task

The effects of presentation of an aversive stimulus and simultaneous failure on a bogus intelligence test upon a subject's aggressive reactions were studied. The subject's fist clenching was used as an indicator of aggression. Four conditions, generated by the combinations of two kinds of stimulus delivered to the subjects (aversive or nonaversive) and two outcomes of the task (failure or success), were investigated. 20 female and 20 male students (ages: 17-34 years) were instructed, upon the reception of an aversive or nonaversive acoustic signal, to press with the right hand a device that displayed a slide. Each slide presented an item from an intelligence test, to which the subjects were either allowed to answer successfully (success) or not (failure). Failure increased the subject's autonomic arousal, as measured by photoplethysmographic sensors, in all stimulation conditions, but only the condition with aversive stimulation increased the speed of clenching. This was interpreted as indicating subject's tendencies to aggression. These results are discussed in relation to the effects of frustration.     

Coordinate frame for symmetry detection and object recognition

Can subjects voluntarily set an internal coordinate frame in such a way as to facilitate the detection of symmetry about an arbitrary axis? If so, is this internal coordinate frame the same as that involved in determining perceived top and bottom in object recognition and shape perception? Subjects were required to determine whether dot patterns were symmetric. Cuing the subjects in advance about the orientation of the axis of symmetry produced a substantial speedup in performance (Experiments 1 and 3) and an increase in accuracy with brief displays (Experiment 2). The effects appeared roughly additive, with an overall advantage for vertical symmetry; thus, the vertical axis effect is not due to a tendency to prepare for the vertical axis. The cuing advantage was found to depend upon the subject's knowing in advance the spatial location as well as orientation of the frame of reference (Experiment 4). The fifth experiment provided evidence that the frame of reference responsible for these effects is the same as the one that determines shape perception: Subjects viewed displays containing a letter (at an unpredictable orientation) and a dot pattern, rapidly naming the letter and then determining whether the dots were symmetric about a prespecified axis. When the top-bottom axis of the letter was oriented the same way as the axis of symmetry for the dots, symmetry judgments were significantly more accurate. Thus, the results suggest a single frame of reference for both types of judgment. The General Discussion proposes a theory of how visual symmetry may be computed, which might account for these phenomena and also characterize their relation to "mental rotation" effects.     

Circumcerebral application of weak complex magnetic fields with derivatives and changes in electroencephalographic power spectra within the theta range: implications for states of consciousness

Relative power within the delta, theta, low-alpha, high-alpha, and gamma electroencephalographic spectra of 8 human volunteers was recorded over the left and right frontal, temporal, parietal, and occipital lobes during and after the circumcerebral application through an array of 8 solenoids of 6 different configurations of weak (5 to 10 microTesla) magnetic fields. The solenoids were equally spaced around the subject's head along a horizontal plane above the ears. An approximately 30% increase in power within the theta band occurred transcerebrally during the application of a specific configuration, previously shown to affect subjective time, involving 20-msec. rates of change in the duration of delivery of the magnetic fields to each successive solenoid. Compared to the left hemisphere, the right hemisphere displayed a 20% increase in power within the 5.0- to 5.9-Hz range for all 6 configurations. The results suggest that very complex magnetic fields with the appropriate temporal parameters rotated around and within brain space can interact with the cerebral processes, measured as specific hands of frequencies, generating consciousness. Implications for the roles of hippocampal theta activity, cortical resonance, and Goldstone bosons in these processes are discussed.     

An illusion of reversed direction in hyperopes

If a subject who is sufficiently farsighted removes his corrective, positive, lenses and looks with one eye from a distance of one or a few meters, at a small lighted area such as the (continuously "on") indicator light of an electric toothbrush, razor, or smoke detector, and if a small object such as a pin is then moved slowly from above to below the subject's eyes (in a plane close to the eye), the subject will perceive the object moving normally from above to below until it encroaches on his view of the lighted area. The object will then be seen to encroach first on the bottom of the lighted area, and as the object continues to move down it will be seen to be moving up across the lighted area, exiting the lighted area at the top. Similarly, an object moved in front of the eye from the subject's left to his right will be seen by the subject to traverse the lighted area in the reverse direction, right to left, even though the subject moves the object himself. Also, while the object is in front of the lighted area, it is perceived as an upside down silhouette having surprisingly clear and sharp edges, and it appears to be located on the lighted area rather than close to the eye where it really is.     

The effects of attenuation of frequency segments on binaural localization of sound

Perceived location of tonal stimuli d narrow noise bands presented in two-dimensional space varies in an orderly manner with changes in stimulus frequency. Hence, frequency has a referent in space that is most apparent during monaural listening. The assumption underlying the present study is that maximum sound pressure level measured at the ear canal entrance for the various frequencies serves as a prominent spectral cue for their spatial referents. Even in binaural localization, location judgments in the vertical plane are strongly influenced by spatial referents. We measured sound pressure levels at the left ear canal entrance for 1.0-kHz-wide noise bands, centered from 4.0 kHz through 10.0 kHz, presented at locations from 60° through ?45° in the vertical plane; the horizontal plane coordinate was fixed at ?90°. On the basis of these measurements, we fabricated three different band-stop stimuli in which differently centered 2.0-kHz-wide frequency segments were filtered from a broadband noise. Unfiltered broadband noise served as the remaining stimulus. Localization accuracy differed significantly among stimulus conditions (p<.01). Where in the vertical plane most errors were made depended on which frequency segment was filtered from the broadband noise.     

Primes, contingent attention, and training: effects on a child's motor behavior

The use of primes, contingent attention, and training sessions to assess a child's engagement and skill in six large motor activities was examined using a combination reversal and multiple-baseline design. Assessment was based on four levels: proximity to equipment, touching equipment, unskilled participation, and skilled participation. Before training, priming (suggestion to the child) was more effective than contingent attention for increasing the subject's engagement (but not skill) in five activities and for increasing skilled participation in one activity. Training of four activities in the natural environment effectively increased the subject's skill level in five activities. Thus, training appeared to generalize to one of these five activities in this setting and also to skillfully executed stair climbing in an adjoining setting. After training, primes and contingent attention were sufficient to maintain both the subject's skill level and engagement in all activities. Postchecks in the same setting the following semester with different teachers revealed only slight increases in participation, as compared to previous baselines, but all participation was at the skilled level. Social interaction, which was not experimentally manipulated, did not systematically vary in relation to changes in experimental conditions.     

Perceptual biases in the horizontal and vertical dimensions are driven by separate cognitive mechanisms

Perceptual attention in healthy participants is characterized by two biases, one operating in the horizontal plane, which draws attention leftward, and the other operating in the vertical plane, which draws attention upward. Given that these biases are reliably found in the same individual, and appear similar at a surface level, a number of researchers have investigated the relationship between horizontal and vertical attentional biases. To date, these investigations have failed to find an association, and this may be due to the fact that one-dimensional vertical and horizontal stimuli were presented separately rather than being measured from a single, two-dimensional stimulus. Across three experiments, two dimensional stimuli were presented, and participants marked the centre of the stimuli. In addition, the shapes of the stimuli were manipulated to determine whether this produced the same modulation of the two biases. Across 13 stimuli and three experiments there were no correlations between the vertical and horizontal biases. In addition, manipulations of stimulus shape, which affected biases in one dimension, did not affect biases in the other dimension. There were, however, consistent correlations between the degree of bias within each dimension across the different stimuli. This study has produced converging evidence that horizontal and vertical biases in spatial judgments rely on separate cognitive mechanisms. To account for these results we discuss a model whereby horizontal asymmetries rely more on space-based mechanisms whereas vertical asymmetries rely more on object-based mechanisms.     

The effect of vertical and horizontal symmetry on memory for tactile patterns in late blind individuals

Visual stimuli that exhibit vertical symmetry are easier to remember than stimuli symmetric along other axes, an advantage that extends to the haptic modality as well. Critically, the vertical symmetry memory advantage has not been found in early blind individuals, despite their overall superior memory, as compared with sighted individuals, and the presence of an overall advantage for identifying symmetric over asymmetric patterns. The absence of the vertical axis memory advantage in the early blind may depend on their total lack of visual experience or on the effect of prolonged visual deprivation. To disentangle this issue, in this study, we measured the ability of late blind individuals to remember tactile spatial patterns that were either vertically or horizontally symmetric or asymmetric. Late blind participants showed better memory performance for symmetric patterns. An additional advantage for the vertical axis of symmetry over the horizontal one was reported, but only for patterns presented in the frontal plane. In the horizontal plane, no difference was observed between vertical and horizontal symmetric patterns, due to the latter being recalled particularly well. These results are discussed in terms of the influence of the spatial reference frame adopted during exploration. Overall, our data suggest that prior visual experience is sufficient to drive the vertical symmetry memory advantage, at least when an external reference frame based on geocentric cues (i.e., gravity) is adopted.     

Auditory psychomotor coordination and visual search performance

In Experiments 1 and 2, the time to locate and identify a visual target (visual search performance in a two-alternative forced-choice paradigm) was measured as a function of the location of the target relative to the subject's initial line of gaze. In Experiment 1, tests were conducted within a 260 degree region on the horizontal plane at a fixed elevation (eye level). In Experiment 2, the position of the target was varied in both the horizontal (260 degrees) and the vertical (+/- 46 degrees from the initial line of gaze) planes. In both experiments, and for all locations tested, the time required to conduct a visual search was reduced substantially (175-1,200 msec) when a 10-Hz click train was presented from the same location as that occupied by the visual target. Significant differences in latencies were still evident when the visual target was located within 10 degrees of the initial line of gaze (central visual field). In Experiment 3, we examined head and eye movements that occur as subjects attempt to locate a sound source. Concurrent movements of the head and eyes are commonly encountered during auditorily directed search behavior. In over half of the trials, eyelid closures were apparent as the subjects attempted to orient themselves toward the sound source. The results from these experiments support the hypothesis that the auditory spatial channel has a significant role in regulating visual gaze.     

Infants' localization of sounds in the median vertical plane: estimates of minimum audible angle

Infants 6, 9, 12, 15, and 18 months of age were seated in a dark room directly facing an array of nine loudspeakers positioned along the median vertical plane. One loudspeaker was positioned at ear level, 0 degree, and four others each were positioned above and below 0 degree. To examine infants' resolution of auditory space in the median vertical plane we sought to determine the smallest angular shift in the vertical location of a sound that infants could reliably detect (i.e., minimum audible angle). A two-alternative forced-choice procedure was used in which a sequence of white noise bursts was presented initially at 0 degree, and then shifted vertically (i.e., above or below 0 degree) and continued to be presented until the infant made a directional response; correct responses were visually reinforced. The smallest angular shift in vertical location that was reliably detected systematically decreased with increasing age between 6 months (15 degrees) and 18 months (4 degrees), suggesting a finer partitioning of auditory space along the vertical axis over this age range. By 18 months infants' performance matched that of a group of adults tested under the same circumstances.