Reaction time,movement time,and intelligence

Speed of information processing is measured in terms of reaction time (RT) and movement time (MT) to five stimulus displays which differ in the amount of information transmitted, over a range from 0 to 3 bits of information. RT, but not MT, increases as a linear function of the number of bits in the stimulus display. RT and MT show reliable individual differences which are significantly correlated with intelligence as measured by Raven's Standard Progressive Matrices.     

Reaction time,movement time,and intelligence: A replication and extension

The purpose of the investigation was to replicate and extend a study by Jensen and Munro which found reaction time (RT) and movement time (MT) parameters to correlate negatively and moderately with Raven matrices performance. A sample of 20 ninth-grade girls was used. Relationships between RT and MT and Raven scores were found to be negative and moderate to high, thus replicating the Jensen and Munro study. In addition, moderate to strong negative correlations were found between RT and MT parameters and reading comprehension and performance on the California Test of Basic Skills. Weaker relationships were found for mathematics and English grades although the direction was consistently negative.     

Feedback control of hand-movement and Fitts' law

Fitt's empirical result is stated and its information theoretic interpretation briefly discussed. An alternate derivation from a model assuming continous velocity control of hand position is shown to fit the motion time data equally well. Detailed studies of hand motion trajectories in Fitts' reciprocal tapping task have confirmed the exponential target approach predicted by this model but also revealed systematic fluctuations that it cannot explain. A further alternate model is therefore presented, based on intermittent feedback with target approach by a sequence of discrete positional corrective motion “impulses”. The second model also predicts motion times in accord with Fitts' Law.

Detailed studies of target aimed translational hand and rotary wrist motions have shown that the intermittent corrective impulses are of approximately Gaussian integral form, with minimum s.d. on the order of 30 msec. for wrist rotation, and recurrence rate about 10/s. Mechanical and physiological interactions capable of explaining this corrective impulse trajectory are discussed, and a model based on balance of forces between agonist and antagonist muscles is briefly developed. The interaction between external (visual) and internal (proprioceptive or kinaesthetic) feedback channels determining impulse amplitude is discussed in the light of results obtained using force disturbance and with amplified, attenuated or delayed visual feedback. It seems that an internal “secondary positional reference” must be postulated to explain results obtained when S is deprived of visual feedback.     

Extending Fitts' law to a three-dimensional pointing task

An attempt was made to extend Fitts' law to a three-dimensional movement (pointing) task to enhance its predictive performance in this domain. An experiment was conducted in which 10 subjects performed three-dimensional pointing movements under the manipulation of target size, distance to target and direction to target. As expected, the duration of these three-dimensional movements was rather variable and affected markedly by direction to target. As a result, the variance in the movement times produced was not satisfactorily explained by the conventional Fitts' model. The conventional model was extended by incorporating a directional parameter into the model. The extended model was shown to better fit the data than the conventional Fitts' model, both in terms of r(2) and the standard error of the residual between the measured movement time and the value predicted by model fit.     

A note on the information-theoretic basis of Fitts' law

Fitts' law is an information-theoretic view of human motor behavior developed from Shannon's Theorem, 17, a fundamental theorem of communications systems. Using data from Fitts' original experiments, we demonstrate that Fitts' choice of an equation that deviates slightly from the underlying principal is perhaps unfounded, and that the relationship is improved by using an exact adaptation of Shannon's equation.     

Fitts' law as a function of system dynamics and target uncertainty

Fins' law was found to hold for discrete movements executed by subjects controlling the velocity of a cursor with a control stick The slope of movement time versus index of difficulty was approximately twice as large as for a comparable position control system. Target uncertainty also increased the slope of total time versus index of difficulty, and this effect is interpreted in terms of adaptive tuning of the human movement system.     

Three-dimensional movement trajectories in Fitts' task: Implications for control

According to Fitts (1954), movement time (MT) is a function of the combined effects of movement amplitude and target width (index of difficulty). Aiming movements with the same index of difficulty and MT may have different planning and control processes depending on the specific combination of movement amplitude and target size. Trajectories were evaluated for a broad range of amplitudes and target sizes. A three-dimensional motion recording system (WATSMART) monitored the position of a stylus during aiming movements. MT results replicated Fitts' Law. Analysis of the resultant velocity profiles indicated the following significant effects: As amplitude of movement increased, so did the time to peak resultant velocity; peak resultant velocity increased slightly with target size, and to a greater extent with increases in the amplitude of movement; the time after peak resultant velocity was a function of both amplitude and target size. Resultant velocity profiles were normalized in the time domain to look for scalar relation in the trajectory shape. This revealed that: the resultant velocity profiles were not symmetrical; the proportion of time spent prior to and after peak speed was sensitive to target size only, i.e. as target size decreased, the profiles became more skewed to the right, indicating a longer decelerative phase; for a given target size, a family of curves might be defined and scaled on movement amplitude. These results suggest that a generalized program (base trajectory representation) exists for a given target width and is parameterized or scaled according to the amplitude of movement.     

Reaction time, intelligence, and attention

The roles of attention in reaction time and in the relationships among reaction time, intelligence, and achievement were analyzed. The subjects were 105 seventh-grade children. The results were generally consistent with most studies involving the Hick paradigm: both mean reaction time and the standard deviation of reaction time correlated with the intelligence and achievement measures used. Reaction time measures were correlated with attention and perceptual speed as well as with general intelligence, or g. Implications of these results for current theories linking reaction time and intelligence are discussed.     

Finger width corrections in Fitts' law: implications for speed-accuracy research

This note points out that using the finger as a test probe in a Fitts task may lead to misleading results, because of the increased target tolerance resulting from the width of the finger pad. An experiment demonstrates the need to use a corrected target width when calculating the index of difficulty; without this correction, information processing rates are overestimated. An example is given of a developmental study in which the finger pad size changes with age. The resulting changes in the calculated rates of information processing are shown to be markedly different for the different age groups.     

A study of Fitts' law on goal-directed aiming task with moving targets

Most research based on Fitts' law define a log-linear relationship between temporal and spatial accuracy in goal-directed aiming tasks using stationary targets. Whether this relationship holds or not when the targets have varying velocities, and how the behavioral strategies and physical activities may change accordingly are of interest. The aim of this study was to investigate the relationship between temporal and spatial accuracy in goal-directed aiming tasks with moving targets. Participants were asked to aim at two target widths using a joystick. Results demonstrated that in a goal-directed aiming task there was a negative effect on performance when target velocity was increased or target width was decreased. Participants moved faster and then made more systematic errors in a high-velocity target condition. Results may be applicable to the complex perceptual-motor behavior of people who perform tasks using computers.     

Increasing the efficiency of instruction for a person with severe disabilities: The applicability of Fitts' law in predicting response time

The purpose of this study was to demonstrate the applicability of Fitts' law in predicting the response duration of instruction-specific head movements for a person with severe multiple disabilities. Fitts' law is a motoric algorithm that calculates an index of difficulty (ID) for responses in relation to the variables of stimulus width and stimulus amplitude. Four functional tasks from the learner's current continuing education plans were targeted: photocopying, using a paint well, model painting, and communication symbol sequencing. For each of the four tasks, two sets of indices were calculated by (1) holding constant stimulus width while varying amplitude, and (2) holding constant stimulus amplitude while varying width. Results showed that response duration varied as a function of ID variation.     

Fitts' law with an isometric controller: effects of order of control and control-display gain

Twenty-four male subjects performed a discrete positioning task using an isometric controller. Two levels of order of control (position and velocity) were factorially crossed with two levels of control-display gain. Fitts' law functions were found for each of the four conditions. The velocity control conditions had significantly steeper slopes than the corresponding position control conditions, but there was no main effect for gain. A predicted interaction between control-display gain and order of control was found, indicating that the relative benefit of high gain is greater for velocity control than for position control. The reaction time (RT) regression lines had steeper negative slopes than those attained by Jagacinski, Repperger, Moran, Ward, and Glass (1980), who used an isotonic controller. This is in agreement with the results of Falkenberg and Newell (1980), who found that as average velocity increases, RT decreases. The components of Fitts' law were investigated, and this showed that the RT finding was due to the amplitude of the target, which covaried with average velocity, but was not due to the width.     

Note on Fitts' law for manipulative temporal motor responses with path constraints.

This paper presents a first-order version of an earlier model by Kv?lseth (1973) of manipulative motor responses involving serial hand movements with different types of movement-path constraints. This model represents a generalization of Fitts' law. Comparisons are also made between experimental movement times obtained and predetermined and motion-time systems predictions.     

Inspection time and measured intelligence.

Ten subjects with WAIS Full Scale IQ scores ranging from 119 to 47 were required to discriminate between two lines of markedly different length, exposed in random order for ten different durations, by pressing one of two keys. Estimates of inspection time gamma, the rate at which sensory input is accumulated and passed to subsequent decision processes, were calculated directly from the psychometric functions obtained gamma was found to correlate negatively with subtests contributing to Performance IQ. There was a substantial degree of consistency between estimates of gamma on two different occasions and training did not appear to affect the index, although differences between the two estimates increased as the value of the first estimate increased. Mean overall response latency did not correlate significantly with intelligence and measures obtained from retarded subjects were very like those reported in similar experimental situations utilizing normal subjects. This unexpected finding is interpreted as suggesting that, in this situation, retarded subjects have been prepared to respond on the basis of less evidence than is usually required by intellectually normal subjects.