Cross-modal perceptual load: the impact of modality and individual differences.

Visual distractor processing tends to be more pronounced when the perceptual load (PL) of a task is low compared to when it is high [perpetual load theory (PLT); Lavie in J Exp Psychol Hum Percept Perform 21(3):451-468, 1995]. While PLT is well established in the visual domain, application to cross-modal processing has produced mixed results, and the current study was designed in an attempt to improve previous methodologies. First, we assessed PLT using response competition, a typical metric from the uni-modal domain. Second, we looked at the impact of auditory load on visual distractors, and of visual load on auditory distractors, within the same individual. Third, we compared individual uni- and cross-modal selective attention abilities, by correlating performance with the visual Attentional Network Test (ANT). Fourth, we obtained a measure of the relative processing efficiency between vision and audition, to investigate whether processing ease influences the extent of distractor processing. Although distractor processing was evident during both attend auditory and attend visual conditions, we found that PL did not modulate processing of either visual or auditory distractors. We also found support for a correlation between the uni-modal (visual) ANT and our cross-modal task but only when the distractors were visual. Finally, although auditory processing was more impacted by visual distractors, our measure of processing efficiency only accounted for this asymmetry in the auditory high-load condition. The results are discussed with respect to the continued debate regarding the shared or separate nature of processing resources across modalities.

Modality and task switching interactions using bi-modal and bivalent stimuli.

Investigations of concurrent task and modality switching effects have to date been studied under conditions of uni-modal stimulus presentation. As such, it is difficult to directly compare resultant task and modality switching effects, as the stimuli afford both tasks on each trial, but only one modality. The current study investigated task and modality switching using bi-modal and bivalent stimulus presentation under various cue conditions: no cue, either task or modality (single cue) or task and modality (double cue), with participants responding to either the identity or the position of an audio-visual stimulus at each trial. In line with previous research, task and modality switching effects showed sub-additive patterns, with switching costs decreasing as pre-stimulus cue information increased. The current data also showed that modality switching costs were more malleable than task switching costs as the former were eliminated when full and single cue information was provided, as well as when participants responded to the more efficiently processed task (position relative to identity). Conversely, task switching costs were only eliminated in the full cue condition, but were present for both tasks and both modalities despite a similar asymmetry in efficiency (vision relative to audition). The data further show that the specific task-modality combination being responded to impacted on combined task- and modality switching effects, with those combinations leading to either the greatest or lowest costs contributing most heavily to sub-additivity.

Re-evaluating visual and auditory dominance through modality switching costs and congruency analyses.

Competition between the senses can lead to modality dominance, where one sense influences multi-modal processing to a greater degree than another. Modality dominance can be influenced by task demands, speeds of processing, contextual influence and practice. To resolve previous discrepancies in these factors, we assessed modality dominance in an audio-visual paradigm controlling for the first three factors while manipulating the fourth. Following a uni-modal task in which auditory and visual processing were equated, participants completed a pre-practice selective attention bimodal task in which the congruency relationship and task-relevant modality changed across trials. Participants were given practice in one modality prior to completing a post-practice selective attention bimodal task similar to the first. The effects of practice were non-specific as participants were speeded post-practice relative to pre-practice. Congruent stimuli relative to incongruent stimuli, also led to increased processing efficiency. RT data tended to reveal symmetric modality switching costs whereas the error rate data tended to reveal asymmetric modality switching costs in which switching from auditory to visual processing was particularly costly. The data suggest that when a number of safeguards are put in place to equate auditory and visual responding as far as possible, evidence for an auditory advantage can arise.

Losses disguised as wins in modern multi-line video slot machines.

AIMS: Players can wager on multiple lines of modern slot machines. When they spin and fail to gain any credits, the machine goes into a state of relative quiet. By contrast, when they spin and win, these spins are accompanied by reinforcing sights and sounds. Such reinforcement also occurs when the amount won is less than the spin wager. We sought to show that these 'losses disguised as wins', or LDWs, would be as arousing as wins, and more arousing than regular losses. MEASUREMENT AND PARTICIPANTS: We measured skin conductance response (SCR) amplitudes and heart-rate changes following wins, LDWs and losses for 40 novices playing a multi-line slot machine. FINDINGS: SCR amplitudes were similar for wins and LDWs-both were significantly larger than for regular losses. CONCLUSIONS: For novice players, the reinforcing sights and sounds of the slot machine triggered arousal on wins, where the number of credits gained was greater than the spin wager, but also on 'losses disguised as wins' where the amount 'won' was less than the spin wager. Despite the fact that players lost money on these spins, these outcomes were more arousing than regular losses where no credits were gained. Although these findings involve novice players, the heightened arousal associated with these losses may have implications for the development of problem gambling, as arousal has been viewed as a key reinforcer in gambling behaviour.