?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=On+the+possible+relations+between+discriminability+and+apparent+magnitude.&rft.creator=Ross%2C+Helen+E.&rft.subject=Perceptual+Cognitive+Psychology&rft.subject=Psychophysics&rft.description=Some+psychophysicists+seek+a+unified+theory+in+which+the+scaling+of+apparent+sensory+magnitude+and+the+discrimination+of+differences+in+intensity+can+be+encompassed.+When+contextual+factors+are+held+constant%2C+there+is+a+positive+correlation+over+many+sensory+continua+between+the+exponent+of+the+power+function+for+sensory+scaling+and+the+inverse+of+the+Weber+fraction.+Variations+in+neural+efficiency+also+show+a+similar+correlation+with+apparent+magnitude+and+discrimination.+The+role+of+other+factors+(such+as+contrast%2C+adaptation+and+size+scaling)+remains+unclear.+Both+Weber+and+Fechner+considered+aspects+of+these+issues.+Weber+held+that%2C+for+the+same+physical+stimulus+intensity%2C+apparent+magnitude+and+discriminatory+ability+increased+with+neural+efficiency.+Fechner+held+that+changes+in+apparent+magnitude+had+no+effect+on+discrimination%3A+a+stable+differential+threshold+was+predicted+by+the+Parallel+Law+(Weber's+Law+applied+to+internal+sensations).+Evidence+is+considered+for+the+tactile+sense+and+weight+perception%2C+and+for+visual+size.+The+relation+between+apparent+heaviness+and+weight+discrimination+is+complex%2C+varying+with+the+state+of+adaptation+and+with+neural+efficiency.+There+is+some+evidence+that+both+tactile+and+visual+apparent+size+increase+with+a+finer+underlying+neural+structure%3B+but+it+is+unclear+whether+other+tyoes+of+increase+in+apparent+size+lead+to+increased+spatial+acuity%2C+or+to+differences+in+the+Weber+fraction+for+line+length.+The+variety+of+values+of+apparent+magnitiude+and+discrimination%2C+and+the+lack+of+a+monotonic+relation+between+them%2C+makes+it+unlikely+that+all+known+relationships+could+be+encompassed+in+a+unified+psychophysical+theory.&rft.date=1997-12&rft.type=Journal+(Paginated)&rft.type=PeerReviewed&rft.format=text%2Fhtml&rft.identifier=http%3A%2F%2Fcogprints.org%2F697%2F1%2FBJMSP2.html&rft.identifier=++Ross%2C+Helen+E.++(1997)+On+the+possible+relations+between+discriminability+and+apparent+magnitude.++%5BJournal+(Paginated)%5D+++++&rft.relation=http%3A%2F%2Fcogprints.org%2F697%2F