An Inhibited Recognition Performance for Explicitly Presented Target-Aligned Irrelevant Stimuli in the Auditory Modality

An Inhibited Recognition Performance for Explicitly Presented Target-Aligned Irrelevant Stimuli in the Auditory Modality Andrew D. Dewald (adewald@hawaii.edu) Department of Psychology, University of Hawaii at Manoa 2530 Dole Street, Honolulu, HI 96822 Scott Sinnett (ssinnett@hawaii.edu) Department of Psychology, University of Hawaii at Manoa 2530 Dole Street, Honolulu, HI 96822 Abstract Overtly presented, but ignored visual stimuli are inhibited in a later recognition task if previously presented synchronously with an attended visual target. Here, we extend these findings to auditory presentations. Participants were required to respond to immediate sound repetitions in a stream of simultaneously presented spoken words, and later given a surprise recognition test that measured recognition for the unattended words. Words that had been simultaneously presented with a sound repetition in the previous repetition detection task were later recognized at levels significantly below chance. These data suggest the existence of an inhibitory mechanism that is exhibited in later recognition tests for salient auditory information that was previously unattended and had been simultaneously presented with an attended auditory target in a separate task. Introduction Anecdotal and scientific evidence suggest that stimuli that receive attention are more efficiently processed than stimuli that go unattended (Ahissar & Hochstein, 1993; Broadbent, 1953; Cherry, 1953; Mack & Rock, 1998; Moray, 1954; Sinnett, Costa, & Soto-Faraco, 2006; Spence & Squire, 2003; Triesman, 1960). However, a number of investigations have demonstrated that unattended information can nevertheless be processed and affect behavior. For instance, researchers have explored how information is processed when it is explicitly or implicitly presented, and the fate of this information when it receives or does not receive direct and focused attention (Rees, Russell, Frith, & Driver, 1999, Seitz & Watanabe, 2003; 2005, Sinnett et al., 2006, Tsushima, Sasaki, & Watanabe, 2006; Tsushima, Seitz, & Watanabe, 2008, Swallow & Jiang, 2010). However, the findings from these investigations fail to yield a clear picture as to the degree to which unattended stimuli can influence behavioral processing. That is, while the presentation of unattended information has consistently lead to behavioral effects, the nature of these effects have ranged from facilitation to inhibition depending on whether it was presented above or below threshold (i.e., explicit awareness). Watanabe, Nanez, and Sasaki (2001, see also Seitz & Watanabe, 2003; 2005) demonstrated significant perceptual learning enhancements in the absence of focused attention for stimuli that were presented below the threshold for visual awareness. Yet, more recently and contrary to these findings, Tsushima and colleagues (Tsushima, Sasaki & Watanabe, 2006; Tsushima, Seitz & Watanabe, 2008) demonstrated that when the implicit stimulus is made explicit (i.e., observable), a later inhibition is observed. Accordingly, behavioral facilitation or inhibition appears to be partly dependent on whether or not stimulus presentation is sub- or superthreshold. Furthermore, collectively these investigations indicate that the temporal relationship between the irrelevant stimulus and an attended target in a separate task is critical to observing these facilitatory or inhibitory effects in a later recognition task. Highlighting the need for temporal synchronicity between attended and unattended stimuli, Seitz and Watanabe’s (2003) participants viewed random moving dot displays with a subthreshold amount of coherent motion (see also Watanabe et al., 2001 for further examples using a similar paradigm). Critically, the subthreshold motion did not influence post exposure motion detection unless it had previously been presented simultaneously with targets from a secondary task (identify white target letters occurring in a rapid serial visual presentation (RSVP) of black and white letters). When this temporal alignment occurred, motion detection improved when subsequently recognizing that same direction after exposure, suggesting that the subthreshold motion had been processed to a degree to facilitate future judgments. Note, the exposure motion was always subthreshold, thereby suggesting that the direction of the motion was implicitly learned to a level sufficient to affect later decisions on motion discrimination. Being that performance enhancements for motions that were not temporally aligned with targets from the secondary task were never observed, the temporal relationship between the task-relevant stimulus (presence of white letter) and the task-irrelevant exposure stimulus (motion) appears to be critical to the effect (Seitz & Watanabe, 2003; 2005). Thus, it would appear that if two stimuli were presented simultaneously, then the learning associated with attention being directed to one stimulus would spill over to the other, thereby facilitating processing of this unattended stimulus. However, it is important to note that the irrelevant stimuli in these investigations were exclusively implicit in nature. As the mechanisms involved in implicit and explicit information processing are likely different, it is important to