The Stroop effect is commonly demonstrated by measuring the time required to identify the colour of the ink (e.g. blue) in which a colour word (e.g. RED) is printed and illustrates a strong interference effect when the prepotent response of processing the word must be inhibited to respond correctly to the colour of the ink. Longer response latencies in colour-identification tasks involving emotional words versus neutral words, an effect dubbed the Emotional Stroop (ES), is often likened to the type of interference found in the Stroop task. However, research has suggested that the effect of attentional modulation in Stroop tasks may be very different from the kind of emotional interference found when comparing reaction times to emotional versus neutral words (McKenna & Sharma, 2004). Proportional congruency experiments using the Stroop task manipulate the amount of incongruity present in a block of trials (Logan & Zbrodoff, 1979), and demonstrate attentional modulation as a change in the size of the Stroop effect such that a greater amount of Stroop interference in a block is associated with a smaller Stroop effect. Manipulating the proportion of interference trials may inform understanding of the differences between Stroop colour-word interference and emotional-word interference. In three experiments, we manipulated the proportion of emotional words in a mixed-list design to study the effect of proportion manipulation on the ES. An enlarged ES was found in blocks of trials that contained more emotional interference; a finding contrary to attentional modulation seen for proportion manipulations of congruency in the Stroop task. The differences between the ES effect and the Stroop effect are discussed, including the role of response incongruity as one possible reason for the discrepancy. / Thesis / Master of Science (MSc) / In three experiments, we investigated the role of proportionally more or less emotional interference on a colour naming task. Emotional interference in the form of emotional words was compared to response interference where participants see mismatched and matched colour words (e.g. the word ‘NIGHTMARE’ in green versus the word ‘BLUE’ in green). We expected participants to be able to learn which blocks contained more emotional word content and to adapt in order to reduce this slow-down effect. Instead, participants were especially slow on emotional words when they were in blocks that contained more emotional word interference. The possible importance of emotional stimuli to participants over the task demands of naming the colour of a word, as compared to other kinds of interference, is discussed.

Participants are slower to identify the print colour of incongruent colour words (e.g., the word ORANGE printed in green) than of congruent colour words (e.g., ORANGE printed in orange). The difference in time between these two conditions is the Stroop effect. The item-specific proportion congruent (ISPC) effect is the observation that the Stroop effect is larger for words that are presented mostly in congruent colours (e.g., BLUE presented 75% of the time in blue), and smaller for words that are presented mostly in a given incongruent colour (e.g., YELLOW presented 75% of the time in orange). One account of the ISPC effect, the modulation hypothesis, is that participants use the distracting word to modulate attention to the word (i.e., participants allow the word to influence responding when it is presented mostly in its congruent colour). Another account, the contingency hypothesis, is that participants use the word to predict the response that they will need to make (e.g., if the word is YELLOW, then the response is probably orange). Reanalyses of data from Jacoby, Lindsay, and Hessels (2003) along with results from new experiments are inconsistent with the modulation hypothesis, but entirely consistent with the contingency hypothesis. A mechanistic account of how responses are predicted is generated from the contingency hypothesis.

Participants are slower to identify the print colour of incongruent colour words (e.g., the word ORANGE printed in green) than of congruent colour words (e.g., ORANGE printed in orange). The difference in time between these two conditions is the Stroop effect. The item-specific proportion congruent (ISPC) effect is the observation that the Stroop effect is larger for words that are presented mostly in congruent colours (e.g., BLUE presented 75% of the time in blue), and smaller for words that are presented mostly in a given incongruent colour (e.g., YELLOW presented 75% of the time in orange). One account of the ISPC effect, the modulation hypothesis, is that participants use the distracting word to modulate attention to the word (i.e., participants allow the word to influence responding when it is presented mostly in its congruent colour). Another account, the contingency hypothesis, is that participants use the word to predict the response that they will need to make (e.g., if the word is YELLOW, then the response is probably orange). Reanalyses of data from Jacoby, Lindsay, and Hessels (2003) along with results from new experiments are inconsistent with the modulation hypothesis, but entirely consistent with the contingency hypothesis. A mechanistic account of how responses are predicted is generated from the contingency hypothesis.

A long-held belief is that human attention can be deployed voluntarily according to observers’ goals (top-down) or shifted automatically to the most salience object in the environment (bottom-up). Recent studies suggest a third category of attentional control: selection history. By this view, an observer’s experience in performing a task that requires the control of attention could automatically affect subsequent attention deployment in the task. This thesis examined selection history mechanisms of attentional control in two visual search phenomena. The first phenomenon is known as the Contextual Cueing Effect (CCE), and refers to an increased search efficiency when a specific distractor configuration is repeatedly associated with a specific target location (Chun and Jiang, 1998). In one study, we found a CCE when one repeated configuration was associated with up to four different target locations, suggesting that the CCE may involve mechanisms other than attentional guidance by one-to-one context-target associations. In another study, we found that the CCE was not affected by concurrent working memory load, and that there was little correlation between the magnitude of the CCE and working memory task performance when measured separately in the same participants. These results suggest that working memory may not be involved in such contextual learning. The second phenomenon is known as the the Item-Specific Proportion Congruent (ISPC) Effect, and refers to item-specific learning that controls the extent to which salient distractors capture attention. Through manual response and eye movement measures, we demonstrate that the ISPC effect reflects the search process itself, rather than processes that precede or follow search. We propose does item-specific learning produces transient changes in the activation of goal-related processes that mediate attention capture. / Thesis / Doctor of Psychology (PsyD) / Where we attend in visual space can be affected involuntarily by memories of how we have attended to visual space in the past. In other words, automatically retrieved memories can control our visual attention independent of volition. This thesis examines two visual search phenomena that display this type of memory-based control over attention. The first phenomenon reveals that search performance improves with experience searching through the same set of visual distractors on multiple occasions. We demonstrate that this form of learning is remarkably flexible; it can occur for multiple targets associated with the same set of distractors. We also demonstrate that this form of learning probably involves long-term rather than short-term memory mechanisms. The second phenomenon reveals how memory-based processes can prevent attention from being captured by a salient distractor. Eye movement data reveal that this form of learning impacts search itself, rather the processes that precede or follow search.

It is a widely held view that humans have control over their food choices and consumption. However, research also suggests that eating behavior is often triggered by contextual cues and guided by automaticities and habits. Interestingly, the dichotomy between automatic and controlled processing has recently been challenged, suggesting that they may be intertwined. In a large female sample (n = 567), we investigated the hypothesis that task-based and self-reported measures of automatic and controlled processing would interact and impact self-reported eating behavior. Results analyzed via structural equation modeling suggest that automatic, but not controlled processing, during a modified flanker task, including a context-specific proportion congruent (CSPC) manipulation, was inversely associated with self-reported self-control. The influence of self-control on unhealthy eating behavior (i.e., uncontrolled and emotional eating, heightened consumption of fat and sugar) was only indirect via habitual behavior, which itself had a strong direct impact. Unhealthy eating was further associated with real-life outcomes (e.g., body mass index (BMI)). Our findings suggest that eating behavior may indeed be guided primarily by automaticities and habits, whereas self-control might facilitate this association. Having self-control over eating might therefore be most effective by avoiding contextual cues eliciting undesired automatic behavior and establishing habits that serve long-term goals.