Enhanced Performance for Recognition of Irrelevant Target-Aligned Auditory Stimuli: Unimodal and Cross-modal Considerations

Enhanced Performance for Recognition of Irrelevant Target-Aligned Auditory Stimuli: Unimodal and Cross-modal Considerations Andrew D. Dewald (adewald@hawaii.edu) Department of Psychology, University of Hawaii at Manoa 2530 Dole Street, Honolulu, HI 96822 USA Scott Sinnett (ssinnett@hawaii.edu) Department of Psychology, University of Hawaii at Manoa 2530 Dole Street, Honolulu, HI 96822 Abstract presented in the background during the letter identification task, of which a small subset moved coherently. Despite the coherent motion being implicit (i.e., participants were unable to reliably detect the coherent motion), participants were proficient at discriminating the motion (still presented below threshold) in a later discrimination task as long as it had previously been exposed simultaneously with the presence of a differently colored target letter during the identification task. It is important to note that the initial motion presentation was implicit. This is a key point, as when presenting the coherent motion above threshold (i.e., 50% of the dots moved coherently), Tsushima et al (2008) showed an inhibition for target-aligned motions. Thus, it appears that facilitatory and inhibitory effects might be dependent on whether the initial presentation was presented below or above threshold, respectively. As the majority of this research has used a relatively non- complex and simple stimuli (e.g., coherent motion in an array of moving dots), we recently examined (see Dewald et al., 2011) how a more salient stimulus, but irrelevant to the primary task, might affect later processing during an adapted inattentional blindness (IB) task (see for example Rees, Ruth, Frith, & Driver, 1999; Sinnett, Costa, & Soto- Faraco, 2006). Participants were required to monitor a stream of pictures that had written words superimposed on top of each image, and respond to immediate repetitions in the picture steam while ignoring the word stream. A subsequently presented surprise recognition test for the previously ignored words demonstrated that words that had been temporally aligned with the presence of a task-target (i.e., an immediately repeating picture) were recognized significantly below chance levels (i.e., inhibited), while words that had been temporally aligned with non-targets (i.e., a non repeating picture) were recognized at chance levels. It is important to note that the highly salient stimuli (written words) were presented for 350 ms (i.e., more than enough time for explicit perception). However, the aligned words were nonetheless inhibited in a later surprise recognition test. This finding dovetails with the earlier described findings by Tsushima et al (2008), who used target-aligned coherent motion as a stimulus and observed an analogous inhibition of motion discrimination for target- Task-irrelevant stimuli are later recognized at enhanced levels providing that they had previously appeared with a task- relevant target (Dewald & Sinnett, submitted; Seitz & Watanabe, 2003, 2005). The present investigation explores this notion in the auditory sensory modality. Participants listened to a stream of auditory sounds and spoken words with the instruction to detect repetitions in only the sound stream (i.e., ignore the words). A surprise test measured recognition for the previously played words. Overall, when comparing target-aligned and non-aligned information in a later recognition task, facilitation was observed for words that had been aligned with target repetitions, despite equal presentation frequency and being irrelevant to the primary repetition task. This enhancement was mediated by the sensory modality of presentation in the surprise recognition task. Congruent auditory presentations between the exposure and recognition tasks yielded improved performance, and under cross-modal presentations the magnitude of the enhancement was greatest. Introduction An emerging body of research has explored how unattended information (explicitly or implicitly presented) that appears simultaneously with a task-target in a separate task is later recognized in a subsequently presented surprise recognition test (Dewald, Sinnett, & Doumas, 2011; Seitz & Watanabe, 2003, 2005; Swallow & Jiang, 2010, 2011; Tsushima, Sasaki, & Watanabe, 2006; Tsushima, Seitz, & Watanabe, 2008). These investigations have generally consisted of a primary task involving visually presented task-relevant and previously irrelevant stimuli, with a later surprise recognition test for the irrelevant stimuli. Collectively, the findings suggest that the task-irrelevant stimuli are indeed processed, as long as they were previously aligned with a task-relevant target. However, two opposing patterns have been observed, with facilitatory (see for example Seitz & Watanabe, 2003; Watanabe, Nanez, & Seitz, 2001) or inhibitory (see for example Tsushima et al., 2006, 2008) effects for the previously aligned, but irrelevant material, seemingly dependent on whether it had originally been presented below or above, respectively, the threshold for conscious awareness. Seitz and Watanabe (2003) required participants to identify differently colored target letters in a rapid serial visual presentation (RSVP) of the letters. Importantly, an array of randomly moving dots (irrelevant to the task) was