Job-specific applicant pools and national norms for personality scales: implications for range-restriction corrections in validation research

This article compares variability in national norms to variability in job-specific applicant pools for personality scales. Across 23,231 job applicants for 111 jobs, we found that job-specific applicant pools were slightly less variable than broad normative data (by about 4%) based on a national norm sample of 40,474 job applicants. For some personality variables, the amount of variability reduction correlated with work characteristics as captured by the Data, People and Things scales of the Dictionary of Occupational Titles (US Department of Labor, 1977). Most correlations were small in magnitude. In general, the small reductions in job-specific applicant pool variability provide evidence that researchers' decisions to use manual norm group standard deviations in range restriction corrections has not appreciably inflated the personality-criterion relationships studied. Implications for attraction and gravitation to jobs are discussed.     

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.     

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.     

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.     

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.     

Brain abnormalities in antisocial individuals: implications for the law

With the increasing popularity in the use of brain imaging on antisocial individuals, an increasing number of brain imaging studies have revealed structural and functional impairments in antisocial, psychopathic, and violent individuals. This review summarizes key findings from brain imaging studies on antisocial/aggressive behavior. Key regions commonly found to be impaired in antisocial populations include the prefrontal cortex (particularly orbitofrontal and dorsolateral prefrontal cortex), superior temporal gyrus, amygdala-hippocampal complex, and anterior cingulate cortex. Key functions of these regions are reviewed to provide a better understanding on how deficits in these regions may predispose to antisocial behavior. Objections to the use of imaging findings in a legal context are outlined, and alternative perspectives raised. It is argued that brain dysfunction is a risk factor for antisocial behavior and that it is likely that imaging will play an increasing (albeit limited) role in legal decision-making.     

Conditions for a linear speed-accuracy trade-off in aimed movements

A linear speed-accuracy trade-off has been found for rapid, precisely timed movements from a home position toward a target point. In this trade-off, W_e = K₁ + K₂(D/T), where D is the distance between the home position and the target, T is a pre-specified movement time, and W_e is the standard deviation of the distances actually moved. This result differs from Fitts' law, the commonly observed logarithmic trade-off in aimed movements. A new experiment with wrist rotations was performed to determine what conditions induce the linear trade-off rather than Fitts' law. Three types of condition are considered: movement brevity, feedback deprivation, and temporal precision. The experiment yielded a linear trade-off for precisely timed movements even when their durations significantly exceeded an amount of time (200 ms) sufficient to process visual feedback. This result suggests that the linearity does not depend on movement brevity and/or feedback deprivation per se. Instead it supports a temporal-precision hypothesis that the linear trade-off occurs when aimed movements must have precisely specified durations.

A linear speed-accuracy trade-off has been found for rapid, precisely timed movements from a home position toward a target point. In this trade-off, W_e = K₁ + K₂(D/T), where D is the distance between the home position and the target, T is a pre-specified movement time, and W_e is the standard deviation of the distances actually moved. This result differs from Fitts' law, the commonly observed logarithmic trade-off in aimed movements. A new experiment with wrist rotations was performed to determine what conditions induce the linear trade-off rather than Fitts' law. Three types of condition are considered: movement brevity, feedback deprivation, and temporal precision. The experiment yielded a linear trade-off for precisely timed movements even when their durations significantly exceeded an amount of time (200 ms) sufficient to process visual feedback. This result suggests that the linearity does not depend on movement brevity and/or feedback deprivation per se. Instead it supports a temporal-precision hypothesis that the linear trade-off occurs when aimed movements must have precisely specified durations.     

The Morton-Massaro law of information integration: implications for models of perception

Information integration may be studied by analyzing the effect of 2 or more sources (e.g., auditory and visual) on participants' responses. Experiments show that ratios of response probabilities often factorize into components selectively influenced by only 1 source (e.g., 1 component affected by the acoustic source and another 1 affected by the visual source). This is called the Morton-Massaro law (MML). This article identifies conditions in which the law is optimal and notes that it reflects an implicit assumption about the statistics of the environment. Adherence to the MML can be used to assess whether the assumption is being made, and analyses of natural stimuli can be used to determine whether the assumption is reasonable. Feed-forward and interactive models subject to a channel separability constraint are consistent with the law.     

Placebo effects in developmental disabilities: implications for research and practice

Recent clinical trials of secretin in children with autism showed robust placebo effects and no benefit of secretin over placebo. This article explores the reasons for the observed placebo effects, focusing on the heightening of positive expectancy by media attention and by the sensory experiences associated with intravenous injections. Comparisons are drawn with research involving other novel treatments and other clinical populations of children with developmental disabilities and neurobehavioral disorders. Research regarding mechanisms of placebo effects is reviewed, including patient and clinician attributes, expectancy effects, participation effects, changes in caregiver behavior, and conditioning. New evidence regarding the biological basis of placebo effects is briefly presented. Since placebo effects are ubiquitous and may operate by a variety of mechanisms, research design is critical in designing clinical trials and in evaluating other outcomes research. Measurement issues important for research in developmental disabilities are emphasized. Ethical concerns have been raised regarding the use of placebo in clinical research, but current analysis suggests that placebo controls are necessary and defensible on ethical grounds, if certain conditions are met. The study of placebo effects ("placebology") holds great promise as a new area of research in therapeutics. The author's research in the potential augmentation of stimulant effects in children with attention deficit/hyperactivity disorder (ADHD) by adding placebo in open label is briefly presented. The placebo has always been integral to the practice of medicine, but advances in scientific medicine and medical ethics have diminished the role and use of placebo in practice. An innovative approach to the ethical use of placebo is proposed.     

Non-linear gaining in precision aiming: making Fitts' task a bit easier

The role of information in the processes underlying kinematic trajectory-formation was examined by manipulating the relation between effector space (movement of a hand-held stylus on a graphics tablet) and task space (movement of a cursor on a screen where targets were presented) in a precision aiming task with five different levels of task difficulty. Movement patterns were found to evolve as a function of the flow of information in task space, with participants (N = 13) producing more rapid and more fluent movements when the mapping between spaces included the softening-spring characteristics typical of behavioural patterns at higher levels of task difficulty. We conclude that the kinematic changes (movement time and pattern) observed when task difficulty increases result from informational influences. Information affects behavioural dynamics at the level of the parameters without affecting the underlying dynamical structure.     

A phase transition model for the speed-accuracy trade-off in response time experiments

Most models of response time (RT) in elementary cognitive tasks implicitly assume that the speed-accuracy trade-off is continuous: When payoffs or instructions gradually increase the level of speed stress, people are assumed to gradually sacrifice response accuracy in exchange for gradual increases in response speed. This trade-off presumably operates over the entire range from accurate but slow responding to fast but chance-level responding (i.e., guessing). In this article, we challenge the assumption of continuity and propose a phase transition model for RTs and accuracy. Analogous to the fast guess model (Ollman, 1966), our model postulates two modes of processing: a guess mode and a stimulus-controlled mode. From catastrophe theory, we derive two important predictions that allow us to test our model against the fast guess model and against the popular class of sequential sampling models. The first prediction--hysteresis in the transitions between guessing and stimulus-controlled behavior--was confirmed in an experiment that gradually changed the reward for speed versus accuracy. The second prediction--bimodal RT distributions--was confirmed in an experiment that required participants to respond in a way that is intermediate between guessing and accurate responding.     

Modifying law enforcement training simulators for use in basic research

Several approaches to using simulation as a method for teaching good judgment in the use of firearms by law enforcement officers and military personnel were investigated for their potential applications to research: the GAMMA Live Fire Video Training System, the FireArms Training Systems Simulator (FATS), and the Judgment Under Stress Training (JUST) simulator. Each instrument uses real-time, computer-controlled, life-sized projected video images of scenarios that may or may not present a threat, and handguns that fire real or simulated ammunition. The subjects respond to a sequence of “shoot/no-shoot” judgment scenarios resulting in data on judgment, reaction time, and accuracy. The JUST simulator was found to be more easily modifiable in capturing data on performance at microanalytic levels. Although true interactive simulations are not feasible with this system, this was not seen as a hindrance to its usefulness for research.     

Correction for fast guessing and the speed-accuracy tradeoff in choice reaction time

In choice reaction time tasks, response latency varies as the subject changes his bias for speed vs accuracy; this is the speed-accuracy tradeoff. Ollman's Fast Guess model provides a mechanism for this tradeoff by allowing the subject to vary his probability of making a guess response rather than a stimulus controlled response (SCR). It is shown that the mean latency of SCR's (μ_s) in two-choice experiments can be estimated from a single session, regardless of how the subject adjusts his guessing probability. Three experiments are reported in which μ_s apparently remained virtually constant despite tradeoffs in which accuracy varied from chance to near-perfect. From the standpoint of the Fast Guess model, this result is interpreted to mean that the tradeoff here was produced almost entirely by mixing different proportions of fast guesses and constant (mean) latency SCR's. The final sections of the paper discuss the question of what other models might be compatible with μ_s invariance.