Article Figures & Data
Figures
- Figure 1.
Psychological task. In each trial, the instruction figure (i.e., the bigger figure that is hollow in the middle) determined which task the volunteers had to perform. If the instruction figure was a square (right), the volunteers had to decide whether the word was bisyllabic (i.e., has two syllables). If the instruction figure was a diamond (left), the volunteers had to decide whether the upcoming word referred to concrete objects. Before the presentation of the instruction, the prime was presented. The prime was a small figure occupying the central space left out in the instruction figure and could also be either square-shaped or diamond-shaped. The instruction figure did not overlap spatially with the prime figure, but their contours did, such that the instruction figure acted as a metacontrast mask for the prime and reduced the visibility of the prime. This was particularly true when the SOA was at 83 ms, as in the Low-Visibility conditions, compared with High-Visibility conditions when the SOA was at 16 ms.
- Figure 2.
Behavioral demonstration of the priming effect. HiVis and LoVis, respectively, refer to the high and low visibility of the primes. Con and InCon refer to the congruency and incongruency between the primes and the instructions. When the primes were incongruent with the instructions, volunteers were primed to perform the alternative (i.e., wrong) task, and their accuracies were lower (left) and response times bigger (right). Interestingly, this was particularly true when the visibility of the primes was low, as reflected by interactions between the factors of Congruency and Visibility in both the accuracies (p = 0.001) and the response times (p < 0.0005). This justifies the claim that the priming effect operates fundamentally at an unconscious level.
- Figure 3.
Neural activity associated with priming. Data were extracted from the brain areas that were previously found to be associated with the Phonological task (left ventral premotor area) and the Semantic task (left inferior frontal cortex and middle temporal gyrus). The location of these is schematically illustrated on the brain above. Here, task relevant means activity from the Semantic areas when the volunteers were instructed to perform the Semantic task, and activity from the Phonological areas when they were instructed to perform the Phonological task. Task irrelevant means the activity was extracted from the alternative areas, which was more important for the primed task than the instructed task. When the visibility of the primes was low (LoVis), which means the priming effect was strongest (see Fig. 2), activity in task-relevant areas was significantly reduced (p = 0.019), and activity in task-irrelevant areas was significantly increased (p = 0.045). This suggests that the volunteers were actually engaged in exercising the wrong neural circuits when they were primed to perform the wrong task. This effect is not present when the visibility of the primes was high (HiVis), suggesting that this effect could not be attributable to the degree of conscious perception of the prime. This is reflected by a three-way interaction between Task Relevance (i.e., activity in task relevant areas vs activity in task irrelevant areas), Congruency (Con; between prime and instruction), and Visibility (of the prime) (p = 0.040). InCon, Incongruency; n.s., not significant.
- Figure 4.
Mid-DLPFC and unconscious priming. We looked for activity in the brain that was associated with the unconscious priming effect in general, regardless of which task was explicitly cued, by testing for the interaction between Congruency (Con; between prime and instruction) and Visibility (of the prime). This test revealed activity in the mid-DLPFC (right; x = −38). This effect was specific to the Low-Visibility condition, in which volunteers did not consciously perceive the primes. InCon, Incongruency; n.s., not significant; HiVis, high visibility; LoVis, low visibility.
Tables
Task Congruency Phonological Semantic Congruent Congruent Phonological Semantic Incongruent Incongruent -
Volunteers could be instructed to perform either the Phonological task or the Semantic task, and the prime in each trial could either be Congruent or Incongruent with the instruction. These were repeated for the conditions in which the primes were of either High Visibility or Low Visibility. Together, these constitute a 2 × 2 × 2 factorial design, with Task, Congruency, and Prime Visibility as experimental factors.
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