It’s under control: Top-down search strategies can override attentional capture

Bacon and Egeth (1994) proposed that observed instances of attentional capture by feature singletons (e.g., color) were the result of a salience-based strategy adopted by subjects (singleton detection mode) and, thus, were not automatic. They showed that subjects could override capture by adopting strategies based on searching for specific target features (feature search mode). However, Theeuwes (2004) has recently argued that Bacon and Egeth’s results arose from experimental confounds. He elaborated a model in which attentional capture must be expected when salient distractors fall within a spatialwindow of attention. According to Theeuwes’s (2004) model, there exist two essential criteria for examining stimulus-driven capture. First, search latencies cannot increase with display size, since the search must be parallel; second, the salience of the irrelevant distractor must not be compromised by characteristics of the search display. Contrary to the predictions of Theeuwes’s (2004) model, we provide evidence that involuntary capture can be overridden when both of these criteria are met. Our results are consistent with Bacon and Egeth’s proposal.     

fMRI of parents of children with Asperger Syndrome: a pilot study

BACKGROUND: People with autism or Asperger Syndrome (AS) show altered patterns of brain activity during visual search and emotion recognition tasks. Autism and AS are genetic conditions and parents may show the 'broader autism phenotype.' AIMS: (1) To test if parents of children with AS show atypical brain activity during a visual search and an empathy task; (2) to test for sex differences during these tasks at the neural level; (3) to test if parents of children with autism are hyper-masculinized, as might be predicted by the 'extreme male brain' theory. METHOD: We used fMRI during a visual search task (the Embedded Figures Test (EFT)) and an emotion recognition test (the 'Reading the Mind in the Eyes' (or Eyes) test). SAMPLE: Twelve parents of children with AS, vs. 12 sex-matched controls. DESIGN: Factorial analysis was used to map main effects of sex, group (parents vs. controls), and sexxgroup interaction on brain function. An ordinal ANOVA also tested for regions of brain activity where females>males>fathers=mothers, to test for parental hyper-masculinization. RESULTS ON EFT TASK: Female controls showed more activity in extrastriate cortex than male controls, and both mothers and fathers showed even less activity in this area than sex-matched controls. There were no differences in group activation between mothers and fathers of children with AS. The ordinal ANOVA identified two specific regions in visual cortex (right and left, respectively) that showed the pattern Females>Males>Fathers=Mothers, both in BA 19. RESULTS ON EYES TASK: Male controls showed more activity in the left inferior frontal gyrus than female controls, and both mothers and fathers showed even more activity in this area compared to sex-matched controls. Female controls showed greater bilateral inferior frontal activation than males. This was not seen when comparing mothers to males, or mothers to fathers. The ordinal ANOVA identified two specific regions that showed the pattern Females>Males>Mothers=Fathers: left medial temporal gyrus (BA 21) and left dorsolateral prefrontal cortex (BA 44). CONCLUSIONS: Parents of children with AS show atypical brain function during both visual search and emotion recognition, in the direction of hyper-masculinization of the brain. Because of the small sample size, and lack of age-matching between parents and controls, such results constitute a pilot study that needs replicating with larger samples.     

Directional uncertainty in visually guided pointing

Studies of the relationship between stimulus-response uncertainty and reaction times indicate three qualitatively different functions: Hick's law, simple-choice step function, or flat curve (no effect at all). The extent of stimulus-response S-R) compatibility appears to interact with the effects of uncertainty on response times. One possible hypothesis regarding these various S-R uncertainty functions is that uncertainty will have an effect whenever the stimuli and their associated responses are not within the same egocentric spatial coordinates. We tested this hypothesis in 5 undergraduate participants (2 men, M age 18.7 yr., range 18-20) by investigating the time-course of pointing to peripherally located visual targets under four different levels of uncertainty (1, 2, 4, or 8 possible locations). Surprisingly, the resulting response function does not match any of those previously reported. Visually guided pointing produced a quadratic reaction time function as S-R uncertainty increases in log2 steps from 1 to 8.