Hemispheric asymmetries in the resolution of lexical ambiguity Jeffrey Coney, Kimberly David Evans Presented by Chris Evans May 17, 2006

Bottom Line Q: Taking dominant meanings, context, and delay between prime and target into account, does the brain activate the dominant meaning first and then activate others as needed, or activate ALL meanings initially and then use the appropriate one, losing the others? A: Yes.

The Brain Left brain: linear, logic, detail, pieces math, science, concrete meanings Right brain: creative, pattern, “big picture”, relationships art, music, connotations, pattern recognition arousal and attention -- ?

The Brain and Vision Subject focuses on point in center of visual field, eliminating the overlap which normally occurs.

Task To identify as a word or non-word a target letter string presented to either the lvf or rvf, after being “primed” by a sentence ending in the prime homograph Target could be related to the dominant or subordinate meaning of the prime, or be unrelated, or be a pronounceable non- word letter string Delay between prime and target varied

Controlled Variables Dominant or subordinate priming Dominant or subordinate trigger word Left or right presentation of trigger word Delay in presenting trigger

Result measures Response times Errors

Complex interactions! Dominant or subordinate priming Agreement of target with prime Delay between prime and target LVF/RVF presentation of target

Method Looked good to me… Choice of subjects (e.g. all right handed) Use of both hands for responses Choice of dominant/subordinate meanings (by experimentation) Careful definition of user experience, and monitoring of user attention T-tests to separate different effects

RT Results – Level 1 Longer SOA resulted in faster correct responses Left hemisphere (RVF) provided faster correct responses Congruence of prime and target meaning resulted in fastest response times; un- related prime and target had slowest response times

RT Results—Level 2 Congruent targets improved most at longer SOA Responses were faster with a dominant target, for either context Left hemisphere was significantly faster with dominant contexts at lower SOA, less so with subordinate contexts and longer SOA

RT Results—Level 3 In-context targets improved more at longer SOA than out-of-context targets Confirmed advantage of dominant target At longer SOA, facilitation decreased for dominant targets, increased for non- dominant targets

RT Results—Level 4 RVF and dominant context: only dominant targets were facilitated LVF and dominant context: facilitation on all conditions EXCEPT incongruent non-dominant target at longer SOA RVF and subordinate context: facilitation only at longer SOA LVF and subordinate context: facilitation of congruent targets and non-congruent targets at longer SOA

Error Results Confirmed RT results No other significant results

Their conclusions Based on low SOA: left hemisphere is strongly sensitive to frequency and also to context; right hemisphere accesses all meanings and gives preference to the dominant only in dominant contexts Based on higher SOA: no differences between LVF/RVF; dominant context resulted in no facilitation of non-dominants; non-dominant context strongly activated non-dominant meaning

Questions?