Does the chance to win money change how we process emotional words?
Expecting to win money and reading an emotional word each changed brain responses, but at different times and in different places, and the two effects did not combine.
Source
Independence of valence and reward in emotional word processing: electrophysiological evidence
Study at a glance
- Design
- Human experiment — Within-subject design crossing word valence (positive, negative, neutral), reward cue (+5 cents gain, -5 cents loss, or nothing at stake) and word concreteness (concrete vs abstract); participants judged each word as concrete or abstract while 64-channel EEG was recorded
- N
- N=18 · 24 students were tested; 4 were excluded for EEG artifacts, 1 for too few trials and 1 for not following instructions, leaving 18 in the analyses
- Population
- Right-handed native-English-speaking UC Berkeley students
- Outcome
- Reaction time and accuracy of concreteness decisions, and event-related potentials (P2, early posterior negativity, N400, late positive complex) to the reward cues and the words
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What they did
Students read 300 English nouns that were positive, negative or neutral, and had to decide as fast as possible whether each was concrete or abstract. Before each word, a cue told them whether a correct answer would win 5 cents, an error would lose 5 cents, or nothing was at stake. EEG was recorded throughout so the researchers could track event-related brain potentials to the cue and to the word, and test whether reward expectancy boosted the brain's response to emotional words.
What they found
Reward cues sped up and slightly improved responses when gain was possible, and the gain cue produced a larger early P2 component to both the cue and the following word. Emotional words, both positive and negative, produced a larger late positive complex about 400-700 ms after the word than neutral words did. Crucially, reward expectancy and word emotion never interacted in behaviour or in any brain measure, suggesting two independent, successive processes. Unexpectedly, emotion helped with abstract words but slowed decisions for concrete words.
The limits
What it doesn't show
The final sample was only 18 students, so the key finding is a null interaction; the authors argue it is not a power problem because the main effects were significant, but small interactions could still be missed. The ERP analysis scanned many 100 ms windows across 64 electrodes without predefined components, which the authors themselves describe as exploratory. Emotional words differed from neutral words in arousal as well as valence, so the design cannot say which of the two drove the effects, and the stakes (5 cents) were small. The concreteness task may have suppressed early emotion effects such as the early posterior negativity, which was not found.
Key terms
- Event-related potential (ERP)
- The average EEG response time-locked to a stimulus, showing brain activity at millisecond resolution as a series of positive and negative peaks.
- Late positive complex (LPC)
- A sustained positive ERP over parietal sites from about 400 ms onwards, larger for emotional than neutral stimuli and thought to reflect deeper processing of motivationally significant material.
- P2
- A positive ERP peak about 150-250 ms after a stimulus at frontal and central sites, linked to selecting task-relevant items.
- Emotional valence
- How positive or negative a stimulus is; here words rated 7 or above were positive and 3 or below were negative on a 9-point scale.
- Reward expectancy
- Anticipation of a gain or loss signalled before a task, here by a cue showing +5, -5 or 0 cents.
- Interaction effect
- When the effect of one factor depends on the level of another; the study's key question was whether reward changed the size of the emotion effect.
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Quiz yourself
What did the cue before each word indicate?
Common questions
If both reward and emotion boost processing, why expect them to interact?
Both have been linked to the dopamine system, so if they share a mechanism, expecting reward should amplify the brain's extra response to emotional words; finding no interaction suggests separate mechanisms.
Did positive and negative words differ from each other?
No. Both produced a similar enlarged late positive complex compared with neutral words, suggesting the brain responds to emotional relevance in general rather than to good versus bad specifically.
Why use a concrete-versus-abstract task instead of asking about emotion?
It forces participants to process word meaning deeply without making emotion part of the task, so any emotion effect reflects automatic processing.
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