More to 3-D vision than meets the eye

Does self-motion affect object recognition? Researchers have long studied how 3-D objects are recognized from different points of view, but have disregarded the observers' own movement by keeping them motionless. A recent study by Simons et al. shows that self-motion cannot be ignored, as it changes the way that objects are recognized.     

Depth perception by the active observer

The connection between perception and action has classically been studied in one direction only: the effect of perception on subsequent action. Although our actions can modify our perceptions externally, by modifying the world or our view of it, it has recently become clear that even without this external feedback the preparation and execution of a variety of motor actions can have an effect on three-dimensional perceptual processes. Here, we review the ways in which an observer's motor actions--locomotion, head and eye movements, and object manipulation--affect his or her perception and representation of three-dimensional objects and space. Allowing observers to act can drastically change the way they perceive the third dimension, as well as how scientists view depth perception.     

Voluntary head movement and allocentric perception of space

Although visual input is egocentric, at least some visual perceptions and representations are allocentric, that is, independent of the observer's vantage point or motion. Three experiments investigated the visual perception of three-dimensional object motion during voluntary and involuntary motion in human subjects. The results show that the motor command contributes to the objective perception of space: Observers are more likely to apply, consciously and unconsciously, spatial criteria relative to an allocentric frame of reference when they are executing voluntary head movements than while they are undergoing similar involuntary displacements (which lead to a more egocentric bias). Furthermore, details of the motor command are crucial to spatial vision, as allocentric bias decreases or disappears when self-motion and motor command do not match.     

Personality characteristics of drug addicts and alcoholics on the Millon Clinical Multiaxial Inventory

The Million Clinical Multiaxial Inventory (MCMI) was administered to 106 alcoholics and 100 addicts in separate VA inpatient rehabilitation treatment programs. The alcoholics scored higher on the personality style scales of Avoidant, Passive-Aggressive, Schizotypal, Borderline and Paranoid, while the opiate addicts scored higher on the Narcissistic personality disorder scale. Separate cluster analyses for both groups further revealed common personality styles among both groups. Several MCMI scales showed significant correlations with age, but in no case were the effects attributed to age larger than 5% of the total variance. The MCMI may alert clinicians to subtle similarities and differences between and among alcoholics and opiate addicts.