Target localization after saccades and at fixation: Nontargets both facilitate and bias responses

ABSTRACT

The image on our retina changes every time we make an eye movement. To maintain visual stability after saccades, specifically to locate visual targets, we may use nontarget objects as “landmarks”. In the current study, we compared how the presence of nontargets affects target localization after saccades and during sustained fixation. Participants fixated a target object, which either maintained its location on the screen (sustained-fixation trials), or displaced to trigger a saccade (saccade trials). After the target disappeared, participants reported the most recent target location with a mouse click. We found that the presence of nontargets decreased response error magnitude and variability. However, this nontarget facilitation effect was not larger for saccade trials than sustained-fixation trials, indicating that nontarget facilitation might be a general effect for target localization, rather than of particular importance to post-saccadic stability. Additionally, participants’ responses were biased towards the nontarget locations, particularly when the nontarget-target relationships were preserved in relative coordinates across the saccade. This nontarget bias interacted with biases from other spatial references, e.g., eye movement paths, possibly in a way that emphasized non-redundant information. In summary, the presence of nontargets is one of several sources of reference that combine to influence (both facilitate and bias) target localization.     

Bimanual Finger Tapping: Effects of Frequency and Auditory Information on Timing Consistency and Coordination

The authors' goal in this study was to probe the basis for an earlier, unexpected finding that preferred-frequency finger tapping tends to have higher frequencies and to be less stable for in-phase than for antiphase tasks. In follow-up experiments, 3 protocols were employed: a preferred-frequency replication in both coordination modes, a metronome-driven matching of the preferred frequencies to each of the coordination modes, and a frequency scaling of both modes. The original findings were affirmed for preferred frequency. Tapping to a metronome had a differential effect on in-phase and antiphase: A more stable coupling across frequencies was exhibited during in-phase. Under frequency scaling, the antiphase pattern decomposed at lower frequencies than did in-phase, but no phase transitions were observed. The loss of stable coordination in both modes was attended by sudden increases in frequency differences between fingers and by phase wandering. The emergence of those effects is discussed in light of asymmetric modifications to the Haken-Kelso-Bunz model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985) and the task constraints of tapping.     

Perceived Occurrence of the Second of Two Closely Spaced Stimuli in a Long Movement

A 75-deg. movement of the arm in the vertical plane was used to examine the conscious perception of the apparent time of occurrence of a reversal signal S₂. A marked perceptual delay was found whether S₂ occurred during or after the reaction time to the first stimulus. This finding was consistent with Henry’s memory drum theory of neuromotor response, as well as with the efference theory of conscious perception proposed by Festinger and associates.     

Adjustments to Local Friction in Multifinger Prehension

The authors studied the effects of surface friction at the digit-object interface on digit forces and moments when 12 participants statically held an object in a 5-digit grasp. The authors changed low-friction contact (LFC) with rayon and high-friction contact (HFC) with sandpaper independently for each digit in all 32 possible combinations. Normal forces of the thumb and virtual finger (VF), an imagined finger with a mechanical effect equal to that of the 4 fingers, increased with the thumb at LFC or with an increase in the number of fingers at LFC. When the thumb was at LFC, the thumb tangential force decreased. The VF tangential force decreased when the number of fingers at LFC increased. The interaction of the local responses to friction and the synergic responses necessary to maintain the equilibrium explain the coordination of individual digit forces.     

Pattern Stability and Error Correction During In-Phase and Antiphase Four-Ball Juggling

The authors studied pattern stability and error correction during in-phase and antiphase 4-ball fountain juggling. To obtain ball trajectories, they made and digitized high-speed film recordings of 4 highly skilled participants juggling at 3 different heights (and thus different frequencies). From those ball trajectories, the authors determined and analyzed critical events (i.e., toss, zenith, catch, and toss onset) in terms of variability of point estimates of relative phase and temporal correlations. Contrary to common findings on basic instances of rhythmic interlimb coordination, in-phase and antiphase patterns were equally variable (i.e., stable). Consistent with previous findings, however, pattern stability decreased with increasing frequency. In contrast to previous results for 3-ball cascade juggling, negative lag-one correlations for catch-catch intervals were absent, but the authors obtained evidence for error corrections between catches and toss onsets. That finding may have reflected participants' high skill level, which yielded smaller errors that allowed for corrections later in the hand cycle.     

An Examination of Rapid Positioning Movements with Spatiotemporal Constraints

Unidirectional positioning movements with spatiotemporal-constraints were examined as a test of impulse-timing theory (Schmidt, 1976; 1980; Wallace, 1981). Movements were examined at the kinematic, kinetic, and neuromuscular levels in three experiments. In the first experiment, displacement was held constant while five different movement times were examined. Both amplitudes and durations of the EMG and the kinetic variables were related to movement time. The results generally support the impulse-timing model. In the second experiment, movements were performed to a target at each of four distances in a constant movement time. EMG and force amplitudes and, unexpectedly, accelerative-force duration were modulated to achieve changes in displacement when movement time was constant. In the third experiment, movement time and displacement were simultaneously varied resulting in four conditions with equal average velocities. The results of this experiment were not as clear and exhibited individual differences. EMG duration did not always vary with changes in movement time. The results of all three experiments could not be adequately accounted for by the impulse-timing model.     

Prevalence of Type D personality and factorial and temporal stability of the DS14 after myocardial infarction in a Swedish population

This study examined the prevalence of Type D personality and the temporal stability, internal consistency, and construct validity of the DS14 at three time points after myocardial infarction. The prevalence was 14.0% during hospitalization, 25.1% at 1 month, and 19.2% at 12 months. A total of 6.1% of the patients were classified as Type D personality at all three assessments, whereas 68.4% were stable non‐Type D and 25.6% changed between personality classifications. The DS14 had stable structural validity, but low temporal stability over time, especially from hospitalization to the 1‐month and 12‐month follow‐ups (κ = 0.365 and 0.397, respectively).     

Felt obligations to reciprocate to an employer,preferences for mobility across employers,and gender: Three-way interaction effects on subsequent voice behavior

Previous research suggests that employees engage in voice behavior to reciprocate for the positive treatment they receive from employers, but less is known about individual differences in employees' willingness to engage in voice behavior to that end. The present study proposes that felt obligations to the organization relate more strongly to voice behavior when employees also have stronger preferences for job stability (rather than job mobility). We also propose that this two-way interaction will be further moderated by gender; specifically, males who feel strong obligations to reciprocate and have strong preferences for job stability are especially likely to engage in voice behavior. Data collected from 209 employees over an 8-month period support both the proposed two-way and three-way interaction effects. Thus, while the norm of reciprocity is widely held, the effects of felt obligations to employers on voice behavior also depend upon both gender differences and individual differences in preferences for job stability.     

Religious syncretism as a sociocultural factor of social security in cross-border regions

This research rationalises the need to consider religious syncretism a crucial factor of social security in cross-border regions. Special attention is paid to determining and studying the specificity of religious syncretism in the conditions of cross-border regions and analysing the role of religious syncretism in the social security of such regions. We used the combination of the different methodological approaches, it is possible to determine the role of religious syncretism as a sociocultural factor of social security in cross-border regions. Religious syncretism creates firm intercultural and interreligious bonds between the ethnic groups that populate cross-border regions; such bonds are notable for a certain historically established system of ordered and stable interactions, which virtually rules out the emergence of conflicts and helps to preserve the functional integrity of state borders.     

Thermal behaviour of poly(methyl methacrylate)/fullerene composite films

ABSTRACT

Poly(methyl methacrylate) films and poly(methyl methacrylate)/fullerene composite films were fabricated by casting from toluene solutions. The mass fraction of fullerene (C₆₀) was varied from 0.05–3?wt. %. The effect of the fullerene (C₆₀) content on the thermal degradation parameters of the composite films was evaluated by thermogravimetric (TG) analysis. It was found that the incorporation of C₆₀ improved the thermal stability of the polymers. The films eventually decomposed in three stages. Incorporation of fullerene caused a change in the distribution of mass loss over the stages of degradation in comparison with the pristine polymer. Using differential scanning calorimetry (DSC), the phase transitions from the glassy state to the elastic one was studied for the examined polymeric materials. New data relating to the effect of C₆₀ on the glass transition temperature of composites with low weight fractions of filler were obtained. Specifically, for films containing up to 0.1 wt. % of C₆₀, a single glass transition temperature was found, whereas for composites with a higher concentration of filler, two glass transition temperatures were recorded.