Simulation study of a decision-making model of squash competition, phase two: Testing the model through the use of computer simulation

This study aims at verifying the inner validity and logic of a squash competition decision-making model through the use of computer simulation. The model defines the cognitive-decisional strategy of the defending player (D) when selecting a motor reaction in response to his opponent's shot. Computer simulation of the model was carried out on a PDP-10 computer using a recent version of UCI-LISP. Protocol analysis data pertaining to the nature of the information D processes when awaiting the attacking player's shot were fed into the simulation program in order to examine the extent to which the model can reproduce decisions reached in various defensive contexts. Simulation results reveal that the proposed model can account for a substantial part of the variation in the speed and accuracy of D's motor reaction in real sport situations. Several factors like time pressure, expectancies, uncertainty, recency and familiarity of the relationship between signal and response appear to affect D's motor response via the cognitive-decisional strategy employed by the defending player. Particular discrepancies observed between simulation results and decisions reached by expert players in specific defensive situations nevertheless indicate that the decision rule utilized within the present model needs to be refined. In this regard, several issues are discussed and suggestions for further simulation studies are put forward in order to account more precisely for the various features characterizing the defensive player's motor reaction in real sporting context.     

Distractor clustering enhances detection speed and accuracy during selective listening

The effects of distractor clustering on target detection were examined in two experiments in which subjects attended to binaural tone bursts of one frequency while ignoring distracting tones of two competing frequencies. The subjects pressed a button in response to occasional target tones of longer duration (Experiment 1) or increased loudness (Experiment 2). In evenly spaced conditions, attended and distractor frequencies differed by 6 and 12 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1048-Hz distractors). In clustered conditions, distractor frequencies were grouped; attended tones differed from the distractors by 6 and 7 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1400-Hz distractors). The tones were presented in randomized sequences at fixed or random stimulus onset asynchronies (SOAs). In both experiments, clustering of the unattended frequencies improved the detectability of targets and speeded target reaction times, Similar effects were found at fixed and variable SO As. Results from the analysis of stimulus sequence suggest that clustering improved performance primarily by reducing the interference caused by distractors that immediately preceded the target.