Hick's Law in a Stochastic Race Model with Speed-Accuracy Tradeoff

We present an analytic solution for a race model of n stochastic accumulators for multiple choice reaction time. We show that to maintain a constant level of accuracy, the response criterion needs to be increased approximately logarithmically with n, to compensate for the increase with n in the likelihood that an incorrect alternative will be most active after any fixed amount of time accumulating information. Assuming that participants monitor and maintain a constant level of performance can then explain the logarithmic dependency of the response latency on n as specified by Hick's law. Moreover, we show that for short time intervals, the Shannon information that observers extract from a stimulus, is predicted to increase linearly with processing time.     

Stimulus duration as a measure of stimulus generalization

Four pigeons in the line-positive group were trained with a vertical line on a green background that signalled intermittent reinforcement while a plain green field signalled extinction. Four pigeons in the line-negative group were trained with the opposite discrimination. Response to a control key terminated any trial and initiated the next trial. The birds also used the control key during generalization tests to control the durations of trials in which various line orientations were presented. These durations were summed to provide generalization gradients of stimulus duration that were positive or negative in accordance with the trained discriminations. In Experiment 2, birds from the line-positive group were tested with a procedure in which the control key was not available on some trials. This provided an independent assessment of response rates to the test stimuli. These rates were used to predict the stimulus durations obtained when the control key was available. The findings supported a general model for the prediction of response distributions among concurrent stimuli from rates observed with single stimuli.     

Not Making Exceptions: A Response to Shue

abstract   This article refutes Henry Shue's claim that in the case of preventive military attacks it is sometimes morally permissible to make an exception to the fundamental principle regarding the inviolability of individual rights. By drawing on a comparison between torture and preventive military attacks, I will argue that the potential risks of institutionalizing preventive military attacks — what I call the Institutionalizing Argument — are far too great to even contemplate. Two potential risks with setting up a bureaucracy which specializes in preventive military attacks will be highlighted: that any preventive military strike may nourish a cycle of violence that will inevitably cause more deaths and destruction than could ever be justified; and that such preventive military strikes may be abused by political leaders in a desperate effort to hold on to power, including democratically elected political leaders working within a democratic framework .     

Choice as a dependent measure in autoshaping: sensitivity to frequency and duration of food presentation.

Previous investigations have shown that rate, latency, and percentage of trials with at least one response are somewhat insensitive measures of the strength of autoshaped responding. In the present studies, these measures were contrasted with the allocation of responding during simultaneous choice tests, a measure of response strength frequently used in operant paradigms. In two experiments, nine pigeons were exposed to a forward pairing autoshaping procedure. Training sessions consisted of the successive presentation of three stimuli, each followed by food on either 100%, 50%, or 0% of the trials. Choice testing involved the simultaneous presentation of the three stimuli. In Experiment I, all pigeons consistently directed their initial choice responses and the majority of subsequent responses to the stimulus always followed by food, despite the fact that during training sessions the response rates of most birds were highest in the presence of the stimulus followed by food on 50% of the trials. In Experiment II, rate, latency, and percentage of trials with at least one response did not change appreciably as a function of duration of feeder presentations. However, choice responding was lawfully affected by duration of feeder presentations. These data suggest that choice is perhaps a more sensitive measure of the strength of autoshaped responding than other, more commonly employed, indices.     

The affective dimension of response elicitation data: a projective measure

In this research, the Rorschach Affective Ratio, a measure for frequency of response elicitation, was used to examine the affective dimension of response elicitation data. The purpose of this study was to apply the Rorschach Affective Ratio to an examination of the psychodynamic roots of political behavior. This measure compares the number of responses to colored cards, considered as emotional stimuli, with those revealed by the other (black and white) cards of the test. Israeli undergraduates (N = 26) completed a questionnaire composed of 20 questions about peace. Participants who were more supportive of the peace process in the Middle East were found to have a lower Affective Ratio than those who were less supportive. This result suggests that measurable affective aspects may be as important as cognitive aspects of response elicitation in understanding an individual's political attitudes.     

Using Arduino microcontroller boards to measure response latencies

Latencies of buttonpresses are a staple of cognitive science paradigms. Often keyboards are employed to collect buttonpresses, but their imprecision and variability decreases test power and increases the risk of false positives. Response boxes and data acquisition cards are precise, but expensive and inflexible, alternatives. We propose using open-source Arduino microcontroller boards as an inexpensive and flexible alternative. These boards connect to standard experimental software using a USB connection and a virtual serial port, or by emulating a keyboard. In our solution, an Arduino measures response latencies after being signaled the start of a trial, and communicates the latency and response back to the PC over a USB connection. We demonstrated the reliability, robustness, and precision of this communication in six studies. Test measures confirmed that the error added to the measurement had an SD of less than 1 ms. Alternatively, emulation of a keyboard results in similarly precise measurement. The Arduino performs as well as a serial response box, and better than a keyboard. In addition, our setup allows for the flexible integration of other sensors, and even actuators, to extend the cognitive science toolbox.     

Pupillary response as a general measure of activation

Pupil size was measured while 30 male college students undertook five tasks respectively concerning, (a) muscle tension induced by the lifting of weights, (b) fear induced by threat of a gunshot, (c) intense stimulation induced by loud pure tones, (d) heightened attention from viewing novel pictures, and (e) pleasantness and unpleasantness in reaction to pictures that differed in terms of their affect-inducing characteristics. Highly regular relationships were found between pupil size and degree of muscle strain and between pupil size and the temporal ordering of events during threat of a gunshot. Significant effects on pupil size also were found for the other three types of stimulation.     

Further explorations with a process model for water jug problems

Subjects performed a water jug task in which the object was to find a sequence of pouring operations that would produce a specified amount of water in each jug. A model for this task is presented and evaluated. The model makes strong assumptions concerning lack of planning in the water jug task. In addition, alternative models incorporating planning assumptions were considered. Alternative models were evaluated in two experiments. All experimental conditions were successfully simulated by making reasonable and well-motivated parameter changes in our model, which assumes no planning. Further, several classes of models incorporating planning assumptions were shown to be inconsistent with the observed results.     

Programming response duration in a precueing reaction time paradigm

To determine whether the duration of certain motor activities can be a prespecified dimension of the motor program, we studied the duration of a motor response and the hand to be used, in a precueing paradigm. The response to be produced (a press on a push-button) was either short or long and involved either the right or the left hand. In Experiment 1, 200 and 700 ms (Block 1) or 700 and 2,500 ms (Block 2) were respectively chosen as short and long durations. No RT difference between short and long appeared when response duration was certain. When response duration was uncertain, RTs were longer for long than for short responses. In addition, the RTs that preceded the 700-ms response were longer in Block 1 than in Block 2. These results suggest that response duration can be programmed up to 2,500 ms and that the relative duration of a response in a given range is more relevant for programming mechanisms than its absolute duration. In Experiment 2, uncertainty concerning the response was maintained constant in a similar precueing paradigm, in which only 700-and 2,500-ms response durations were considered. The RTs preceding a long duration were shorter when duration was certain than when neither side nor duration was certain. No RT difference appeared before the short response duration. This seems to confirm that duration can be programmed up to 2,500 ms and also suggests that the program elaborated for the short duration constitutes a common basis for short and long responses: When duration is uncertain, programming a long duration requires just an additional operation to complete the program corresponding to the short duration, which has already been selected by default.     

The phobic stimuli response scales: a new self-report measure of fear

Data from two large undergraduate samples were used to develop the phobic stimuli response scales (PSRS). Factor analyses of data from the first sample (N = 380) led to the creation of several scales, two of which (Social and Blood-Injection Fears) demonstrated good reliability and convergent validity. Analyses of data from a second sample (N = 330) were used to modify the three remaining scales (Animal, Bodily Harm, and Physical Confinement Fears), which also showed sound psychometric properties. As predicted, the PSRS were differentially correlated with neuroticism and extraversion, which may represent predisposing factors for these phobic responses. These new scales improve our understanding of the individual differences that are associated with various fears.