On the selection of endogenous and exogenous signals.

Alerting is one of the three components of attention which involves the eliciting and maintenance of arousal. A seminal study by Posner et al. (Posner MI, Klein R, Summers J, Buggie S. 1973 Mem. Cognit. 1, 2-12 (doi:10.3758/BF03198062)) focused on how changing the interval between an alerting signal and a target would impact the speed and accuracy of responding. Participants indicated whether targets were presented on the left or right side of the fixation point. Auditory warning signals were played at various intervals prior to the target to alert participants and prepare them to make a response. Reaction times revealed a robust, U-shaped, preparation function. Importantly, a clear speed-accuracy trade-off (SAT) was observed. In the current experiment, we replicated the methodological components of this seminal study while implementing a novel auditory warning signal (Lawrence MA, Klein RM. 2013 J. Exp. Psychol. General 142, 560 (doi:10.1037/a0029023)) that was either purely endogenous (change in quality without a change in intensity; analogous to isoluminant colour change in vision) or a combination of endogenous and exogenous (change in both quality and intensity). We expected to replicate the U-shaped preparation function and SAT observed by Posner and colleagues. Based on Lawrence and Klein's findings we also expected the SAT to be more robust with the intense signal in comparison to the isointense signal.

The independence of endogenous and exogenous temporal attention.

Temporal attention is the focusing of perceptual resources at a particular point in time. Valid temporal cue information has the capability to improve performance by reducing reaction times, while invalid information has the possibility of impairing performance. The performance difference between valid and invalid conditions is called a temporal cueing effect (TCE). We explored how different alerting mechanisms interact with a participant's ability to utilize temporal information cues, using the Kingstone (The Quarterly Journal of Experimental Psychology, 44(1), 69-104, 1992) temporal cueing paradigm. Extracting the alerting procedure from Lawrence and Klein (Journal of Experimental Psychology: General, 142(2), 560-572, 2013), one of two different temporally contingent warning signals were presented to participants during a trial. The "hi-intensity" warning signal increases intensity and elicits both exogenous and endogenous alerting mechanisms. The "no-intensity" warning signal is isointense relative to baseline and elicits only endogenous alerting mechanisms. Two experiments conducted previously using a discrimination task showed interference between the signal intensity and task difficulty, where the "no-intensity" signal failed to elicit TCEs. In the present study, we implemented a detection task, reducing the mental effort required for a response. The results showed equal TCEs in both signal conditions. We argue for independence of these alerting mechanisms, by way of Sternberg's (Acta Psychologica, 30, 276-315, 1969) additive factor method. Arguments contrasting what mechanism is being impacted by this paradigm are further outlined.