• Attention capture: Stimulus, group, individual, and moment-to-moment factors contributing to distraction

      Stokes, Kirk; Department of Psychology
      Over four studies, some containing multiple experiments, attention capture is explored in a variety of experimental contexts. The over-arching goals were to better understand attention capture at the stimulus level (Chapter 2), the group and the individual-differences level (Chapters 3 and 4), and in terms of moment-to-moment fluctuations in susceptibility to distraction by task-irrelevant stimuli (Chapter 5). Rare or unexpected stimulus changes are known to capture attention and disrupt behavioural performance. Detection is typically thought to depend on changes to the physical properties (e.g., tone pitch) of a stimulus. Chapter 2 explores whether physical change is a necessary antecedent for attention capture. Here, evidence suggests that unexpected semantic change is sufficient to produce a distraction effect and that an accompanying physical/acoustic change is not required to induce semantic processing of task-irrelevant stimuli even when the semantic deviants are unrelated to the primary task. Attention capture is typically robust at the group level and has been observed in a variety of popular paradigms. Chapter 3 explores whether attention capture can be viewed as a stable and generalizable individual trait. The study examined involuntary attention capture across a set of prototypical stimulus-driven capture tasks and contingent-capture tasks in both spatial and/or temporal paradigms. Results showed the expected pattern of capture in each of the tasks as well as modest to good test-retest reliability over the span of one week for each of the capture measures. However, no evidence is found for a common attention capture factor providing evidence that attention capture within an individual is reliable but not generalizable. Chapter 4 extends the results of Chapter 3 and shows that attention capture in these tasks is not related to off-line self-report measures of attentional ability and day-to-day functioning. The lack of evidence for a common factor that can predict attention capture in one or more paradigms suggests that attention capture is not characterized by trait individual differences in executive function or predicted by individuals’ meta-awareness of their own attentional ability. Chapter 5, however, shows that attention capture can be characterized by moment-to-moment lapses of attention as it varies trial-to-trial as a function of internally generated task-irrelevant thought (i.e., mind-wandering). Mind-wandering slowed RTs overall and increased non-contingent, but not contingent, forms of capture providing evidence that some forms of attention capture are exacerbated by moment-to-moment lapses of attention. Self-reports on a dispositional mind-wandering scale did not predict capture when mind-wandering was used as an individual differences variable. Results suggest that attention capture may be better explained by cognitive processes engaged moment-to-moment rather than individual dispositions.
    • Individual Differences in Global/Local Processing Bias and the Attentional Blink

      Dale, Gillian; Department of Psychology (Brock University, 2014-01-27)
      When the second of two targets (T2) is presented temporally close to the first target (T1) in rapid serial visual presentation, accuracy to detect/identify T2 is markedly reduced as compared to longer target separations. This is known as the attentional blink (AB), and is thought to reflect a limitation of selective attention. While most individuals show an AB, research has demonstrated that individuals are variously susceptible to this effect. To explain these differences, Dale and Arnell (2010) examined whether dispositional differences in attentional breadth, as measured by the Navon letter task, could predict individual AB magnitude. They found that individuals who showed a natural bias toward the broad, global level of Navon letter stimuli were less susceptible to the AB as compared to individuals who showed a natural bias toward the detailed, local aspects of Navon letter stimuli. This suggests that individuals who naturally broaden their attention can overcome the AB. However, it was unclear how stable these individual differences were over time, and whether a variety of global/local tasks could predict AB performance. As such, the purpose of this dissertation was to investigate, through four empirical studies, the nature of individual differences in both global/local bias and the AB, and how these differences in attentional breadth can modulate AB performance. Study 1 was designed to examine the stability of dispositional global/local biases over time, as well as the relationships among three different global/local processing measures. Study 2 examined the stability of individual differences in the AB, as well as the relationship among two distinct AB tasks. Study 3 examined whether the three distinct global/local tasks used in Study 1 could predict performance on the two AB tasks from Study 2. Finally, Study 4 explored whether individual differences in global/local bias could be manipulated by exposing participants to high/low spatial frequencies and Navon stimuli. In Study 1, I showed that dispositional differences in global/local bias were reliable over a period of at least a week, demonstrating that these individual biases may be trait-like. However, the three tasks that purportedly measure global/local bias were unrelated to each other, suggesting that they measure unique aspects of global/local processing. In Study 2, I found that individual variation in AB performance was also reliable over a period of at least a week, and that the two AB task versions were correlated. Study 3 showed that dispositional global/local biases, as measured by the three tasks from Study 1, predicted AB magnitude, such that individuals who were naturally globally biased had smaller ABs. Finally, in Study 4 I demonstrated that these dispositional global/local biases are resistant to both spatial frequency and Navon letter manipulations, indicating that these differences are robust and intractable. Overall, the results of the four studies in this dissertation help clarify the role of individual differences in attentional breadth in selective attention.