Clock Test Research Articles

Visuospatial functioning and spatial orientation in a community-based sample of healthy very old persons

A population-based sample ( n = 219) of healthy older adults ranging from 75 to 96 years of age was examined in tests measuring visuospatial ability (modified Block Design Test) and spatial orientation (Clock Setting Test and Clock Reading Test). Results indicated an age-related deterioration in both visuospatial abilities and spatial orientation. Block Design performance was higher under self-paced than under paced conditions across the entire age range, although the beneficial effects from decreased pacing tended to increase with increasing age. Also, the clock test data suggest that the abilities underlying time recognition (clock reading) may deteriorate later in the normal aging process than those underlying time drawing (clock setting). Finally, regression analyses on the relationship between a variety of demographic, psychometric, and biological variables and visuospatial functioning showed that, in order of importance, years of age, Mini Mental State Examination (MMSE), and education, were significantly related to task performance.

Age-related differences in three tests of visual imagery.

Adult age differences were explored on 3 short tests of the ability to generate and manipulate mental images. Age-related decrements were found in all 3 tests and were especially marked on the Clock Test. The tests are all reliable, as shown by test-retest reliability coefficients. Correlations also revealed that the Brooks Letter Test and the East-West Test appear to tap one common underlying ability, whereas the Clock Test measured a somewhat different ability. The East-West and Clock tests, in particular, may provide rapid and easily administered assessments of age-related changes in aspects of mental imagery.

The Clock Test: A Sensitive Measure To Differentiate Normal Elderly from Those with Alzheimer Disease

To examine the clinical utility of the Clock Test for identifying dementia. Group comparisons. A hospital-based out-patient diagnostic clinic. Volunteer sample of elderly individuals (normal elderly, NE, n = 62) and a referred sample of probable Alzheimer Disease (AD, n = 58) patients meeting NINCDS-ADRDA criteria. The Clock Test is composed of three components: Clock Drawing, Clock Setting, and Clock Reading. A detailed scoring system for qualitative as well as quantitative evaluation of Clock Drawing errors was used. Five time settings, varying in level of complexity, were used to evaluate Clock Setting and Clock Reading. The groups differed significantly on Clock Drawing, Clock Setting, and Clock Reading (P less than 0.001). On Clock Drawing, the AD group made significantly more errors of omission and misplacement of numbers than the NE group (P less than 0.001). Using cut-off scores derived to maximize separation between the groups to define deficits in performance, the sensitivity and specificity for the diagnosis of AD of Clock Drawing, Clock Setting, and Clock Reading were 92% and 86%, 87% and 97%, 92% and 85%, respectively. Using a criterion of deficits on two or more of the three components, sensitivity and specificity increased to 94% and 93%, respectively. Deficits on clock drawing in AD may be reflective of a generalized disturbance in the conceptualization of time rather than constructional apraxia, per se. The functionally relevant components of Clock Setting and Clock Reading combined with Clock Drawing make the Clock Test particularly useful as a screening and research tool for AD.

Daytime sleepiness and performance among healthy 80 and 20 year olds

This study investigated the relationship of daytime sleepiness and performance on a vigilance test in a sample of 10 healthy men and 13 women in their 80s (mean age 83.0 ± 3.1 years) and 18 men and 12 women in their 20s (25.0 ± 3.1). We hypothesized that “successfully” aged healthy individuals would have more daytime sleepiness with differentially greater decrements in performance than a younger comparison group. Daytime sleepiness was measured physiologically by the Multiple Sleep Latency Test (MSLT) and through self-report by the Stanford Sleepiness Scale (SSS). Morning and evening performance was measured with the Mackworth Clock Test of vigilance. The major findings were the absence of correlation between either MSLT or SSS daytime sleepiness with performance measures, no difference in daytime sleepiness between the old and young groups and performance decrements among the healthy elderly on all parameters. Results suggest that the modest decrements in performance among the elderly cannot be attributed to daytime sleepiness.

Combined probabilistic testability calculation and compact test generation for PLAs

PLAs (programmable logic arrays) may be tested internally by self-test, or externally by applying test patterns. Fault coverage by nonexhaustive self-test is assured by computing a lower bound for estimated fault coverage vs. test pattern number. First, a lower bound for probabilistic detectability per fault is computed by a method based on Shannon's expansion theorem. In the process of finding a lower bound detectability for a particular fault, a test pattern for the fault is generated automatically, at no extra cost. These patterns often contain several don't cares. Traditional test pattern compaction is then applied to the test pattern set. In addition, a novel test pattern compaction method is introduced, suitable for embedded circuitry. The method may be used in conjunction with a serial scan architecture, whereby each test pattern is shifted one position before being applied to the circuit under test. The compaction scheme was applied to a benchmark set of 53 PLAs. An average reduction of 70% in the number of test bits and clock cycles was achieved.1

Computerized Mackworth vigilance clock test

A computirized vigilance test, the Mackworth clock test, is described. The program runs on IBM-compatible XT and AT computers with a graphics adapter.

AT&T's new approach to the synchronization of telecommunication networks

A description is given of AT&T's nationwide synchronization network along with a tutorial on the importance of and need of synchronization. The primary reference clock (PRC) is described along with its verification methodology, capabilities, and performance. The clock and transmission models are discussed along with methods of specifying and testing clock performance. Planning tools and methodology for the synchronization of private digital networks are presented. An expert system that uses the clock models to prepare the optimum performance synchronization plan for a private network is introduced. >

Cognitive Function in Middle-aged Snorers and Controls: Role of Excessive Daytime Somnolence and Sleep-Related Hypoxic Events

Association of snoring and cognitive function was studied in 46 habitually snoring men ages 41-52 years, and 60 occasionally or never-snoring control male subjects of the same age group. Sleep recordings with monitoring of apneas and hypopneas were made with the static-charge sensitive bed method. Blood oxygen saturation was measured with an oximeter and the snoring sounds were recorded with a microphone after clinical and neuropsychological assessment. A questionnaire with items on excessive daytime somnolence (EDS), sleep, and snoring quality was also used. EDS (as measured by items on the questionnaire) associated with tests requiring concentration, memory retention, and verbal and spatial skills in the habitual snorers group. The number of oxygen desaturation episodes exceeding 4% associated with defective delayed Recall of Logical Stories of the Wechsler Memory Scale and with spatial orientation (Clock test) in the habitual snorers' group even after adjusting for age and obesity.

Evaluation of cognitive impairment using a computerized neuropsychological test battery

The psychometric tests currently used in psychopharmacology were developed many years ago. Computerization of such tests offers better possibilities of standardization and use in efficient repeated measures designs. The Automated Psychological Test (APT) system runs on any Apple II micro, and comprises a set of eleven basic procedures which are particularly suitable for psychopharmacological research. In addition to general purpose procedures for collecting questionnaire and analogue ratings data, API includes a maze test, reaction time modules, finger tapping tests, a test of rate of perspective reversals, a digit span test, a trailmaking test, a lexicon decision test of verbal skills, a symbol digit test which also taps short-term associative memory, and a classical vigilance test, the continuous clock test. The tests have been applied in a series of studies. The cognitive impairment profile of 18 schizophrenic patients was analysed, and related to clinical data and morphological deviance. A group of se...

A New Economical Implementation for Scannable Flip-Flops in MOS

A New implementation for scannable flip-flops in MOS is economical for use in systems that use single latch design. The "System Latch-Scannable Flop" (SL-SF) requires two additional transfer gates, two test clocks, and possibly a test mode signal. Hardware pernalties paid in SL-SF can be the least among other implementations with equivalent test functionality. This article discusses SL-SF only in the context of its scan-path implementation; its applicability to linear feedback shift-register-based self-test should be obvious.

Atomic clocks for astrophysical measurements

Recently developed atomic hydrogen masers have achieved stability well into the 10−16 domain for averaging time intervals beyond 1000 sec and future devices promise further improvements. These devices are very adaptable for space use in very high precision measurements of angle through Very Long Baseline Interferometry (VLBI) and range and range-rate through Doppler techniques. Proposed space missions using these clocks will be discussed for the measurement of the sun's gravity field distribution and tests of gravitation and relativity including a search for pulsed low frequency (∼0.001 Hz) gravitational waves, and orbiting VLBI stations. Estimates of system performance capability will be discussed and the accuracy capability of relativistic measurements evaluated in terms of results from the 1976 NASA/SAO spaceborne clock test of the Einstein Equivalence Principle.

Age regression: A comparison of children's behaviour with the behaviour of adult simulators

The performance of four year old and seven year old children was compared with the performance of adults asked to simulate the behaviour of children of these two age groups. The tasks used were a Word Association Test and the Clock Test (Reifi & Scheerer, 1959). It was found that four year old children differed from seven year old children in their performance on both tests and that adults were able to simulate successfully the performance of seven year olds but not that of four year olds.

Influence of knowledge of results on performance in a monitoring task.

Vigilance performance was tested in six independent groups with a modified version of the Mackworth Clock Test. The groups constituted a 3 × 2 design with (a) no knowledge of results, observer-presented knowledge of results, and machine-presented knowledge of results as one dimension, and (b) physical presence or absence of an observer in the test cubicle as the other variable. All groups were retested without knowledge of results one and seven days after the initial test. On the initial test day, groups with no knowledge of results and machine-presented knowledge of results showed the typical decrement function throughout the session. In contrast, Ss receiving verbal knowledge of results from the experimenter showed less decrement and a significantly higher over-all performance. The superiority of the groups receiving the verbal report persisted on the two subsequent test days despite the fact that all extrinsic knowledge of results was withdrawn on these tests. Observer-presented knowledge facilitated performance regardless of the physical presence or absence of the observer in the test cubicle.

Performance on a Simple Vigilance Task in Noise and Quiet

Twenty subjects, working individually, monitored a simple vigilance task, a modified “Mackworth Clock Test,” for 134 hr in noise (112.5 db SPL) and for 134 hr in quiet (79 db SPL). No difference in efficiency attributable to noise level was found. This result is in conflict with previous reports from this and other laboratories which ascribed decrement in performance on vigilance tasks to noise levels. Vigilance tasks in which performance decrements due to noise were found, differed from the present task in that they required subjects to scan a series of displays in addition to maintaining vigil over each display. It is, therefore, suggested that flexibility of attention may be affected by noise, whereas vigilance without the requirement for flexibility may be unaffected.

The Relation of an Environmental Variable to Performance in a Prolonged Visual Task

In a previous paper (Fraser, 1950) on the relation between angle of display and performance in a prolonged visual task (Mackworth's Clock Test), it was suggested that the presence or absence of the experimenter might affect performance on vigilance tasks. In Mackworth's original experiments (Mackworth, 1950) the subject was in a closed cabinet by himself, and as far as possible all external noise and stimuli were excluded. In the angle of display experiment, the writer sat in the same room as the subject, out of his sight, and there was no particular attempt to exclude the ordinary external noises, etc. It seemed worth while to follow up the previous experiment with another to test the hypothesis that the presence or absence of the experimenter might influence performance in such a task. A new apparatus was devised for this purpose, which possesses some advantages over the Clock Test.

The Relation between Angle of Display and Performance in a Prolonged Visual Task

An experiment is described to test the relation between angle of display and performance in prolonged visual tasks, using the Clock Test in three positions of display surface, vertical, at an angle of 45 degrees to the horizontal, and horizontal. In every case the line of regard was kept at right-angles to the display surface. The results indicate that significantly fewer stimuli are missed in the vertical position of the display surface than in the other two. The deterioration observed in the second half-hour of the original Clock Test experiments was not found in the present experiment, and two possible reasons for this are discussed briefly.

INTELLIGENCE AND PSYCHOSIS

Abstract according to diagnosis of 102 psychotic cases examined by the Stanford intelligence scale: par. 1-11. Retests: par. 12-13. Scattering: of tests: par. 14-20. Technical considerations and criticisms of detail: par. 25-34. Incidents: par. 35-42. Cases dominated by volitional disturbance: par. 43-51. Cases with IQ above 1.00: par. 52-74. "Intelligence" as ideational capacity, distinguished from capacities for dealing with concrete things, or adjustments to other personalities: par. 75-87. Interrelations of intelligence, psychosis, happiness and general adaptation: par. 88. 1. This study is based upon examination in 102 cases of mental disease. The observations cover a period between September, 1916, and July, 1917, and from February, 1919, to April, 1919. The number examined represents approximately the cases in McLean Hospital within these periods from whom the necessary cooperation was obtainable. The percentage of admissions thus susceptible to examination was about 60. The material is not otherwi...