Form-specific visual priming for new associations in the right cerebral hemisphere

Abstract

In three experiments, we examined the internal processing mechanisms of relatively independent visual-form subsystems. Participants first viewed centrally presented word pairs and then completed word stems presented beneath context words in the left or right visual field. Letter-case-specific priming in stem completion was found only when the context word was the same word that had previously appeared above the primed completion word and the items were presented directly to the right cerebral hemisphere. This pattern of results was not found when participants deliberately recollected previously presented words when completing the stems. Results suggest that holistic processing, not parts-based processing as assumed in many contemporary theories of visual-form recognition, is performed in a subsystem that distinguishes specific instances in the same abstract category of form and that operates more effectively in the right hemisphere than in the left hemisphere.The ability to distinguish specific instances in the same abstract category of visual form is an important human faculty. One can differentiate a particular cup from other cups as well as an individual's signature from other written versions of the same set ofletters. An interesting aspect of this ability is that most theories of visual-form recognition, aside from theories that address only face recognition (e.g., Bruce & Young, 1986;Rhodes, 1985), do not focus on how it is accomplished. Most theories focus instead on the ability to distinguish different abstract types of visual forms (e.g., Biederman, 1987;Morton, 1979). Of course, the latter ability is also important and interesting. One can distinguish a cup from a pen, as well as the word form "cup" from the word form "pen," even when the input is an instance that has not been seen before. In the research reported in this article, we tested whether at least relatively independent processing subsystems support the two abilities. More importantly, we examined form-specific priming for novel holistic structures to test whether holistic processing, as opposed to parts-based processing of the sort assumed in many contemporary theories of visual form recognition (e.g., Biederman, 1987;Morton, 1979), characterizes the operations in a subsystem that distinguishes specific instances in an abstract category of form. VISUAL-FORM SUBSYSTEMSWe hypothesize that a specific visual-form (SVF) subsystem underlies recognition of specific instances of forms and operates more effectively in the right cerebral hemisphere (RH) than in the left cerebral hemisphere (LH). In contrast, an abstract visual-form (AVF) subsystem supports recognition of abstract categories of forms and operates more effectively in the LH than in the RH. These subsystems likely focus on different properties of visual-form inputs to achieve different goals. SVF SubsystemIn order to produce different outputs when different instances in the same abstract category appear as inputs, an SVF subsystem must process a form's visually distinctive information ef...

Dissociating Prelexical and Postlexical Processing of Affective Information in the Two Hemispheres: Effects of the Stimulus Presentation Format

“…They were asked to focus on the central fixation cross on the screen (approximately 1 cm ϫ 1 cm in size) presented for 2000 ms. A word or a nonword was then presented tachistoscopically in the periphery of the screen (adjusted to the vertical midline) for 160 ms with a subtending visual angle of at least 2.0°m easured between the inner edge of the stimulus and the center of the fixation cross (the average angle measured from the center of the stimuli to the center of the fixation cross was ϳ6°). These parameters were similar to (or exceeded) those successfully employed by Marsolek and colleagues (Marsolek, Kosslyn, & Squire, 1992;Marsolek, Squire, Kosslyn, & Lulenski, 1994;Marsolek, Schacter, & Nicholas, 1996). Stimulus displays were masked immediately by a noisy pattern of small white dots.…”

Interactive Visual and Postvisual Processes and Their Roles in Form-Specific Memory.

“…Our suggestion would be that it is because they used very unfamiliar fonts and presentation formats (e.g., upside down and backward printed words). We have found in previous research (Marsolek et al, 1996) that preexperimentally novel visual forms are special in that they require attention to perceptual information during encoding for the form-specific representations to be created in the first place. In contrast, familiar forms, such as those used in the present study, are well known and well represented preexperimentally.…”

“…Error bars indicate the (95%) "within-subjects confidence interval" (Loftus & Masson, 1994). visual and postvisual representations, at least when the encoding task involves deep processing. The reason why form-specific memory was observed when stems were presented directly to the right hemisphere but not when they were presented directly to the left hemisphere in Experiment 2 likely is that a form-specific subsystem of visual neocortex operates effectively in the right hemisphere, independently of a more abstract visual subsystem (for further evidence, see Marsolek et al, 1992Marsolek et al, , 1994Marsolek et al, , 1996Marsolek et al, , 2004.…”

“…This is important because storage of preexperimentally novel forms (e.g., words in highly unusual fonts, which may not match preexisting representations precisely) appears to require a specific subsystem in the right hemisphere (see Marsolek, 2004). This subsystem can store novel visual forms effectively, because it is effective at processing visual wholes and the novel information in unfamiliar forms is in their holistic configurations (see Marsolek et al, 1996). There may be a limit, however, to the finding that visually unusual words are stored effectively in a specific subsystem when perceptual identification is used.…”

Real-world categories don't allow uniform feature spaces – not just across categories but within categories also

“…Indeed, recent evidence from a study of visual priming supports this conclusion (Marsolek et al 1996). Participants first read centrally presented word pairs (one word above the other in each pair) and then completed word stems presented beneath context words in the left or right visual field.…”