How Do We See a Changing World?

This chapter begins an analysis of how we see changing visual images and scenes. It explains why moving objects do not create unduly persistent trails, or streaks, of persistent visual images that could interfere with our ability to see what is there after they pass by. It does so by showing how the circuits already described for static visual form perception automatically reset themselves in response to changing visual cues, and thereby prevent undue persistence, when they are augmented with habituative transmitter gates, or MTM traces. The MTM traces gate specific connections among the hypercomplex cells that control completion of static boundaries. These MTM-gated circuits embody gated dipoles whose rebound properties autonomically reset boundaries at appropriate times in response to changing visual inputs. A tradeoff between boundary resonance and reset is clarified by this analysis. This kind of resonance and reset cycle shares many properties with the resonance and reset cycle that controls the learning of recognition categories in Adaptive Resonance Theory. The MTM-gated circuits quantitatively explain the main properties of visual persistence that do occur, including persistence of real and illusory contours, persistence after offset of oriented adapting stimuli, and persistence due to spatial competition. Psychophysical data about afterimages and residual traces are also explained by the same mechanisms.

Numerical Magnitude Processing in Deaf Adolescents and Its Contribution to Arithmetical Ability

Although most deaf individuals could use sign language or sign/spoken language mix, hearing loss would still affect their language acquisition. Compensatory plasticity holds that the lack of auditory stimulation experienced by deaf individuals, such as congenital deafness, can be met by enhancements in visual cognition. And the studies of hearing individuals have showed that visual form perception is the cognitive mechanism that could explain the association between numerical magnitude processing and arithmetic computation. Therefore, we examined numerical magnitude processing and its contribution to arithmetical ability in deaf adolescents, and explored the differences between the congenital and acquired deafness. 112 deaf adolescents (58 congenital deafness) and 58 hearing adolescents performed a series of cognitive and mathematical tests, and it was found there was no significant differences between the congenital group and the hearing group, but congenital group outperformed acquired group in numerical magnitude processing (reaction time) and arithmetic computation. It was also found there was a close association between numerical magnitude processing and arithmetic computation in all deaf adolescents, and after controlling for the demographic variables (age, gender, onset of hearing loss) and general cognitive abilities (non-verbal IQ, processing speed, reading comprehension), numerical magnitude processing could predict arithmetic computation in all deaf adolescents but not in congenital group. The role of numerical magnitude processing (symbolic and non-symbolic) in deaf adolescents' mathematical performance should be paid attention in the training of arithmetical ability.