Investigating trial types putatively evidencing semantic conflict in the Stroop task

Interference in the Stroop task is thought to arise from various stages of processing, including the semantic and response stages. Different experimental methods have been used in an attempt to dissociate the cognitive processes involved in these stages. The work presented in this thesis evaluates two such methods that have been popular, namely the use of a two-to-one response mapping variant of the task and using colour-word distractors that are not valid response options (non-response set trials). The results from a series of experiments which utilised behavioural and eye-tracking measures, provided (Bayesian) evidence that two-to-one mapping trials do not involve additional interference compared to non-word neutral trials. Studies that have utilised this method are likely to have been measuring facilitation instead of the intended semantic-based interference, which has obvious ramifications to the conclusions of those studies. The experiments that evaluated non-response set trials indicated them as a better alternative, although during the course of the investigation, it was found that the make-up of Stroop interference is affected by experimental design. This is problematic to extant models of selective attention, as they cannot account for such findings. This led to further investigations of the cognitive mechanisms involved in processing relevant and irrelevant information during the Stroop task. The findings revealed that bottom-up implicit learning processes have a greater role in the allocation of attention and establishing task relevant stimuli, than previously thought. These concepts have generally not been given much consideration in theoretical accounts and the results from these experiments highlight their importance. The methodological and theoretical implications of the findings in this thesis are discussed in the context of theories of selective attention in the Stroop task and automaticity

Linking cognitive control to language comprehension: proportion congruency effects in syntactic ambiguity resolution

Two experiments investigated the effect of sustained cognitive control engagement on syntactic ambiguity resolution. Participants heard (Experiment 1) or read (Experiment 2) garden path sentences like “Put the kiwi on the rectangle on the circle”, in which “on the rectangle” could temporarily reflect either a destination of “Put” or modifier of “kiwi”, and they viewed visual arrays with a kiwi on a rectangle and an empty rectangle and circle. Cognitive control was manipulated experimentally by interleaving sentence trials among either mostly incongruent or mostly congruent Stroop trials. Across both experiments, garden path mouse cursor movements to incorrect destinations were reduced when sentence trials were interleaved among mostly incongruent Stroop trials, and in Experiment 2, garden path reading time effects were also reduced in this condition. These results suggest that a high proportion of incongruent trials supports the sustained engagement of cognitive control and causally improves sentence comprehension across (i.e. spoken and written) modalities

Trial type mixing substantially reduces the response set effect in the Stroop task.

The response set effect refers to the finding that an irrelevant incongruent colour-word produces greater interference when it is one of the response options (referred to as a response set trial), compared to when it is not (a non-response set trial). Despite being a key effect for models of selective attention, the magnitude of the effect varies considerably across studies. We report two within-subjects experiments that tested the hypothesis that presentation format modulates the magnitude of the response set effect. Trial types (e.g. response set, non-response set, neutral) were either presented in separate blocks (pure) or in blocks containing trials from all conditions presented randomly (mixed). In the first experiment we show that the response set effect is substantially reduced in the mixed block context as a result of a decrease in RTs to response set trials. By demonstrating the modulation of the response set effect under conditions of trial type mixing we present evidence that is difficult for models of the effect based on strategic, top-down biasing of attention to explain. In a second experiment we tested a stimulus-driven account of the response set effect by manipulating the number of colour-words that make up the non-response set of distractors. The results show that the greater the number of non-response set colour concepts, the smaller the response set effect. Alternative accounts of the data and its implications for research debating the automaticity of reading are discussed

Primacy of mouth over eyes to perceive audiovisual Mandarin lexical tones

The visual cues of lexical tones are more implicit and much less investigated than consonants and vowels, and it is still unclear what facial areas contribute to facial tones identification. This study investigated Chinese and English speakers’ eye movements when they were asked to identify audiovisual Mandarin lexical tones. The Chinese and English speakers were presented with an audiovisual clip of Mandarin monosyllables (for instance, /ă/, /à/, /ĭ/, /ì/) and were asked to identify whether the syllables were a dipping tone (/ă/, / ĭ/) or a falling tone (/ à/, /ì/). These audiovisual syllables were presented in clear, noisy and silent (absence of audio signal) conditions. An eye-tracker recorded the participants’ eye movements. Results showed that the participants gazed more at the mouth than the eyes. In addition, when acoustic conditions became adverse, both the Chinese and English speakers increased their gaze duration at the mouth rather than at the eyes. The findings suggested that the mouth is the primary area that listeners utilise in their perception of audiovisual lexical tones. The similar eye movements between the Chinese and English speakers imply that the mouth acts as a perceptual cue that provides articulatory information, as opposed to social and pragmatic information

EXPRESS: The Role of Contingency and Correlation in the Stroop Task

Facilitation (faster responses to Congruent trials compared to Neutral trials) in the Stroop task has been a difficult effect for models of cognitive control to explain. The current research investigated the role of word-response contingency, word-colour correlation, and proportion congruency in producing Stroop effects. Contingency and correlation refers to the probability of specific word-response and word-colour pairings that are implicitly learnt while performing the task. Pairs that have a higher probability of occurring are responded to faster, a finding that challenges top-down attention control accounts of Stroop task performance. However studies that try to experimentally control for contingency and correlation typically do so by increasing the proportion of incongruent trials in the task, which cognitive control accounts posit affects interference control via the top-down biasing of attention. The present research focused on whether facilitation is also affected by contingency and correlation while additionally looking at the effect of proportion congruency. This was done in two experiments that compared the typical design of Stroop task experiments (i.e., having equal proportions of Congruent and Incongruent trials but also contingency and correlational biases) to: a) a design that had unequal congruency proportions but no contingency or correlation (Experiment 1), and b) a design where the correlation is biased but proportion congruency and contingency were not (Experiment 2). Results did not support the hypotheses that contingency or correlation affected facilitation. Interference was almost halved in the alternative design of Experiment 2, demonstrating an effect of contingency learning in typical measures of Stroop interference

Response Time Distribution Analysis of Semantic and Response Interference in a Manual Response Stroop Task.

Previous analyses of response time distributions have shown that the Stroop effect is observed in the mode (μ) and standard deviation (σ) of the normal part of the distribution, as well as its tail (τ). Specifically, interference related to semantic and response processes has been suggested to specifically affect the mode and tail, respectively. However, only one study in the literature has directly manipulated semantic interference, and none manipulating response interference. The present research aims to address this gap by manipulating both semantic and response interference in a manual response Stroop task, and examining how these components of Stroop interference affect the response time distribution. Ex-Gaussian analysis showed both semantic and response conflict to only affect τ. Analyzing the distribution by rank-ordered response times (Vincentizing) showed converging results as the magnitude of both semantic and response conflict increased with slower response times. Additionally, response conflict appeared earlier on the distribution compared to semantic conflict. These findings further highlight the difficulty in attributing specific psychological processes to different parameters (i.e., μ, σ, and τ). The effect of different response modalities on the makeup of Stroop interference is also discussed

EXPRESS: Onset complexity and task conflict in the Stroop task

The present study examined the extent to which a key marker of task conflict, negative facilitation, is modified by onset complexity. Negative facilitation, slower RTs to congruent stimuli than to non-lexical neutral stimuli in the Stroop task, is thought to reflect competition between the task sets of colour naming and word reading in the Stroop task (also known as task conflict). That is, it reflects competition between whole task sets, over and above any competition between specific responses associated with a stimulus. An alternative account of negative facilitation argues that it reflects the specific phonological processing differences between pronounceable (e.g., congruent) and non-pronounceable (e.g., xxxx) stimuli that are magnified by the specific task contexts that produce negative facilitation (a mostly non-lexical trial context). Here we used onset complexity to manipulate pronounceability of the irrelevant words in the Stroop task to test this alternative account. However, before applying manipulations that produce negative facilitation, we initially tested whether there was an effect of onset complexity on Stroop task performance. The results from Experiment 1 (and 3) showed that complex onsets led to larger positive facilitation and congruency effects relative to simple onsets, but did not modify incongruent or neutral word RTs. Experiment 2 directly tested whether onset complexity modifies negative facilitation and provided strong evidence for no effect of onset complexity, contrary to the alternative account predictions. The implications of the results for task conflict theory, selective attention and phonological processing in the manual response Stroop task are discussed

Do Task Sets Compete in the Stroop Task and Other Selective Attention Paradigms?

Task sets have been argued to play an important role in cognition, giving rise to the notions of needing to switch between active task sets and to control competing task sets in selective attention tasks. For example, it has been argued that Stroop interference results from two categories of conflict: informational and task (set) conflict. Informational conflict arises from processing the word and is resolved by a late selection mechanism; task conflict arises when two task sets (i.e., word reading and colour identification) compete for activation and can be construed as involving an early selection mechanism. However, recent work has argued that task set control might not be needed to explain all of the switching cost in task switching studies. Here we consider whether task conflict plays a role in selective attention tasks. In particular, we consider whether S-R associations, which lead to informational conflict, are enough on their own to explain findings attributed to task set conflict. We review and critically evaluate both the findings that provided the original impetus for proposing task conflict in selective attention tasks and more recent findings reporting negative facilitation (longer RTs to congruent than to neutral stimuli) – a unique marker of task conflict. We then provide a tentative alternative account of negative facilitation based on poor control over informational conflict and apply it to a number of paradigms including the Colour-Object interference and Affordances tasks. It is argued that invoking competition between task sets in selective attention tasks might not be necessary

Assessing stimulus–stimulus (semantic) conflict in the Stroop task using saccadic two-to-one color response mapping and preresponse pupillary measures

© 2015, The Psychonomic Society, Inc. Conflict in the Stroop task is thought to come from various stages of processing, including semantics. Two-to-one response mappings, in which two response-set colors share a common response location, have been used to isolate stimulus–stimulus (semantic) from stimulus–response conflict in the Stroop task. However, the use of congruent trials as a baseline means that the measured effects could be exaggerated by facilitation, and recent research using neutral, non-color-word trials as a baseline has supported this notion. In the present study, we sought to provide evidence for stimulus–stimulus conflict using an oculomotor Stroop task and an early, preresponse pupillometric measure of effort. The results provided strong (Bayesian) evidence for no statistical difference between two-to-one response-mapping trials and neutral trials in both saccadic response latencies and preresponse pupillometric measures, supporting the notion that the difference between same-response and congruent trials indexes facilitation in congruent trials, and not stimulus–stimulus conflict, thus providing evidence against the presence of semantic conflict in the Stroop task. We also demonstrated the utility of preresponse pupillometry in measuring Stroop interference, supporting the idea that pupillary effects are not simply a residue of making a response

Linking cognitive control to language comprehension: proportion congruency effects in syntactic ambiguity resolution

Two experiments investigated the effect of sustained cognitive control engagement on syntactic ambiguity resolution. Participants heard (Experiment 1) or read (Experiment 2) garden path sentences like “Put the kiwi on the rectangle on the circle”, in which “on the rectangle” could temporarily reflect either a destination of “Put” or modifier of “kiwi”, and they viewed visual arrays with a kiwi on a rectangle and an empty rectangle and circle. Cognitive control was manipulated experimentally by interleaving sentence trials among either mostly incongruent or mostly congruent Stroop trials. Across both experiments, garden path mouse cursor movements to incorrect destinations were reduced when sentence trials were interleaved among mostly incongruent Stroop trials, and in Experiment 2, garden path reading time effects were also reduced in this condition. These results suggest that a high proportion of incongruent trials supports the sustained engagement of cognitive control and causally improves sentence comprehension across (i.e. spoken and written) modalities.</p