Rejection Task Research Articles

Speed control design for an experimental vehicle using a generalized gain scheduling approach

Describes the design and experimental evaluation of a nonlinear automotive speed control system. The approach implemented is based on interpolation of multiple linear controllers designed using multiple local linear models. This is a generalized form of gain scheduling since the models and controllers take explicit account of both stationary and nonstationary (off-equilibrium) operating points. The paper focuses on engineering aspects and experimental evaluation in a test vehicle. The nonlinear controller is tested on a range of speed-profile tracking tasks, and in a disturbance rejection task (the vehicle is driven up a 10% slope). For comparison, linear controllers are implemented. The proposed nonlinear control approach gives excellent performance over the complete operational range. The nonlinear controller can directly account for the strong plant nonlinearities and the engineering constraints.

Another look at reasons for choosing and rejecting.

Students indicated which of two options they would choose or reject in a between-subjects task-frame manipulation. Alternatives had either high or low variability of feature values, corresponding to enriched and impoverished alternatives, respectively. Previous research has yielded mixed results of task framing, with Shafir (1993) demonstrating greater preference for the enriched alternative in choice than rejection but Ganzach (1995) demonstrating the opposite result. An accentuation model explained these differences by postulating that the greater demands for justification in the choice task lead to accentuation of differences between alternatives in choice. The accentuation model was tested against weight-change models in two experiments, one using various decision scenarios and the other using four-trait adjective descriptions of potential roommates. Results were consistent with accentuation theory and inconsistent with a systematic change in weighting of positive and negative attributes across choice and rejection tasks.

Cognitive influences on electrocortical and heart rate activity in obsessive-compulsive disorder

The present study examined patterns of electrocortical and heart rate activity in obsessive-compulsive (OC) patients, and both high and low trait anxious control groups. Physiological patterns were examined in light of an intake-rejection attentional paradigm. For each group, electrocortical and cardiac activity were recorded during conditions of mental rest and mental activity requiring the internal versus external processing of information. The pattern of heart rate activity observed in the present study validated the choice of tasks used to examine intake and rejection attentional processes. Overall, the study reported three major findings. First, at baseline, both OC patients and high trait anxious subjects showed a pattern of activity in their EEG spectrum that differed significantly from low trait anxious subjects. Second, similar heart rate differences for the intake and rejection tasks were detected in all three groups. Third, EEG patterns unique to OCs were evidenced in the frontal region during intake and rejection tasks.

Attention tasks and EEG power spectra

The authors attempted to observe differences in alpha and beta hemispheric asymmetry during a task in which attention was directed toward input from the environment (intake task) as opposed to tasks that required that environmental events be excluded from the focus of attention (rejection tasks). In comparison to resting, both attention tasks caused a shift in alpha asymmetry ratios toward increased power on the right, with the greatest effect at temporal leads. The only significant difference between attention tasks was a finding of higher alpha power during intake than during rejection. Some characteristics of the EEG during attention indicate potential clinical utility.

Effects of intake and rejection tasks on auditory fatigue

The effects of sensory intake and rejection tasks on auditory fatigue were examined in 14 male subjects. Auditory thresholds, psychophysical tuning curves and physiological measures of cardiovascular function were obtained before, during, and following a 7 min 110 dB SPL white noise exposure. Acceleration of heart rate was observed under the sensory rejection (mental arithmetic) condition, and poorer post-exposure auditory thresholds and larger Q10 tip values (measured during late post-exposure intervals) were seen when the task required counting of interruptions in the noise. However, Q10 tip values obtained 1 to 2 min post-exposure, when cochlear effects are maximal, failed to confirm a significant difference as a function of task.

Haemodynamic and electrodermal correlates of psychogenic stimuli in hypertensive and normotensive subjects

This study compared tonic and phasic cardiovascular and electrodermal activity in subjects having essential arterial hypertension (HT) with that of sex- and age-matched normotensive (NT) controls. Fourteen subjects of each group were subjected to ‘sensory intake’ (letter identification) and ‘rejection’ (mental arithmetic) tasks while recordings were made of: systolic and diastolic arterial blood pressure, hand and forearm blood flows, heart rate, skin conductance level and fluctuations. The rejection task affected more physiological variables in both groups than the intake task did. The reaction pattern was similar in both groups. Except for systolic and diastolic blood pressures tonic cardiovascular and electrodermal activity of the HT group was not different from that of the NT group. The same pattern, although less clear cut, was observed when reactivity was studied. According to analyses based on pressure levels both tasks raised the systolic blood pressure of the HT group, whereas only the rejection task raised systolic blood pressure in the NT group. In contrast, an analyses based on blood pressure changes from base to task indicated that both groups increased systolic blood pressure to both tasks. Since virtually no other differences in reactivity were found, this study offers weak support for the notion that subjects having essential arterial hypertension are pressor hyper-reactors.

Autonomic myocardial influences as a factor determining inter-task consistency of heart rate reactivity.

ABSTRACTThis study assessed the consistency of subjects’relative heart rate (HR) responsivity across four tasks and examined the role played by autonomic myocardial influences on this consistency. HR responses across tasks were predicted to covary to the extent that they reflected a similar autonomic mediation, assessed by measurement of pulse transit time (PTT).Forty‐eight male subjects performed two sensory intake (Tones and Lights RT) and two sensory rejection (Mental Arithmetic and Word Formation) tasks. Consistency of HR responsivity was revealed by significant positive correlations observed between HR changes during all task pairs. High HR reactors in rejection tasks displayed HR decreases during an intake task (Tones), whereas low reactors displayed the expected bradycardia. Significant correlations between HR and PTT changes suggested that SNS influences were evoked by mental arithmetic, whereas a dissociation of these indices in the Tones task implied a predominance of PNS influence in that task. Nevertheless, HR changes covaried reliably between these tasks, suggesting that HR responsivity is consistent across situations evoking different patterns of autonomic influence on the heart.

Physiological response patterns during ‘intake’ and ‘rejection’ tasks

Two 2-min tasks, one requiring outer-directed attention (intake task), the other a mental arithmetic task (rejection task) were presented to 20 subjects. According to Lacey the distinguishing feature of the response to intake task are cardiac deceleration and blood pressure decreases. None of these responses was obtained. Some variables, however, were only affected by one of the task; the intake task led to a decreased hand (skin) blood flow and an increased hand vascular resistance, whereas a heart rate acceleration and increased forearm (muscle) blood flow and decreased forearm vascular resistance were observed during the rejection task. Blood pressure, respiration rate and skin conductance were similarly affected by the two tasks. Inconsistencies among previous studies of the response to the two types of tasks were discussed and found to be partially explained by methodological differences.

Organismic, stimulus and task determinants of phasic and tonic heart rate and skin conductance changes

The effects of three variables (perceptual style ‘leveling-sharpening’, stimulus intensity and task) on tonic and phasic heart rate and skin conductance responses were studied. 24 levelers and 24 sharpeners received a series of 25 auditory stimuli under two instructions (task): in one task the subject had to listen carefully to possible small differences between tones (intake task) and in the other task the subject had to count back silently and could neglect the tones (rejection task). One third of each group received tones of 50 dB, one third 75 dB and one third 100 dB. Results show that task has a strong effect on tonic responses in the direction predicted from Lacey's intake-rejection hypothesis. There is hardly any effect of task on phasic responses: only at the first trial heart rate tends to decelerate more in the intake than in the rejection task. Stimulus intensity does not influence tonic responses but very strongly affects phasic responses: deceleration to 50 and 75 dB, acceleration to 100 dB. GSR amplitude increases monotonically as a function of stimulus intensity. There is no difference between levelers and sharpeners with regard to tonic responses. Concerning phasic heart rate, sharpeners decelerate more than levelers and levelers have greater GSRs than sharpeners. It is suggested that tonic changes are relatively more under cognitive control, whereas phasic changes are more of a non-cognitive reflex-like nature. A relationship between the distinction arousal-activation as proposed by Pribram and McGuinness (1975) and the results of this experiment was suggested.

Heart rate and skin conductance responding during three attention-direction tasks under distraction conditions

This study investigated the possibility that a failure to find cardiac acceleration to an environmental rejection task in a previous study was due to insufficient distraction in the experimental situation. The study was replicated, with distracting events added. An environmental intake task was associated with heart-rate deceleration during the first 60 sec. The rejection task and a third task involving attention to bodily events were not associated with significant heart-rate change. There were no differences in skin-conductance responding to the three tasks.