week 3 Flashcards
(7 cards)
emotional stimuli
Categorisation is fundamental to perception, and by extension to other cognitive processes.
Depends on a combination of bottom-up (i.e., info from the stimulus) and top-down processes (i.e., prior knowledge, expectations)
Emotions of the brain
You may remember a structure called the amygdala from last year’s BBB module:
A small, almond-shaped structure forming part of the limbic system involved in emotion processing
Receives sensory (e.g., visual) inputs and sends information onwards to other neural structures
The amygdala plays an important part in giving emotional stimuli privileged access to cognitive processing:
Enhanced memory for positive/negative stimuli is related to level of amygdala activity at encoding (Hamann et al., 1999)
Patients with amygdala lesions (damage) do not show enhan
Visual search
Search for a target among a field of distractors
RTs to find target are recorded and compared across a range of set sizes (N distractors)
Feature vs. conjunction searches – does the target differ on one or multiple features?
This method has been adapted to study possible enhancing effects of emotional target stimuli
This has been found to reflect both quicker orienting of attention (attention drawn to emotional stimulus) and slower disengagement (Flykt, 2005)
Attentional blink
Attentional blink (AB) is a phenomenon where the 2nd of two rapidly presented targets is not consciously registered/reported
Uses a technique called rapid serial visual presentation (RSVP)
‘Blink size’ is about 200-500 ms (see Shapiro et al., 1997)
Anderson (2005) investigated whether effects were specific to negative stimuli, or present for both valences;
and whether they could be explained by word distinctiveness (possible confound)
He found that having an emotional target word (taboo words like anus and herpes) tended to improve accuracy at reporting
Perceptual identification
Another way of testing the processing advantage of emotional stimuli is using a forced-choice perceptual identification task:
Single very brief stimulus (word)
Followed by mask to prevent further processing
Two alternative choices then appear, and ppt has to select the one they think they saw.
Attentional bias view
Implicit bias to detect emotionally significant stimuli (Ratcliff & McKoon, 1997)
Internal mechanism separate from perceptual processing
Consistent with wider models of attentional control systems (Corbetta & Shulman, 2002; Vuilleumier, 2005)
Perceptual enhancement view
Emotional stimuli receive enhanced perceptual encoding, in addition to possible attentional bias (Zeelenberg et al., 2002)
In other words, a positive word (e.g. ‘good’) should produce more visual activation than a similar neutral word (e.g. ‘gone’; see Schupp et al., 2003)
Background Mood and Attention
As well as investigating emotion inherent to the stimuli, we can look at background emotional states (or traits) in the observer
For instance, what effect does background anxiety have on performance in visual attention tasks?
A meta-analysis by Bar-Haim et al. (2007) looked at the level of attentional bias (tendency to focus on negative/threatening stimuli) in different anxious and non-anxious populations.
In the emotional Stroop, RTs to name/identify the colour of the word are compared for neutral-word trials (left) and negative trials (right)
Negative emotional words are expected to exogenously ‘capture’ attention, leading to slower responses.
A ‘Stroop effect’ can be computed for each ppt as the difference between average RTs in the two conditions.
Explaining Attentional Bias in Anxiety
The standard interpretation is that individuals high in anxiety exhibit higher threat sensitivity than others.
Quicker to respond to negative/threatening cues in the environment, and slower to disengage (see Posner & Peterson, 1990).
There is evidence that this may partly be explained by differences in amygdala function, discussed earlier (Rauch et al., 2003);
There is also evidence of differences in interoceptive prediction signals provided by the anterior insula (Paulus & Stein, 2006)
N.B. The insula is a neural structure embedded underneath the major brain lobes (frontal and temporal)
