Calibration of a color monitor for visual psychophysics

It has become common for stimuli used in visual psychophysical experiments to be presented on high-resolution color cathode-ray tubes (CRTs) such as the Barco CDCT 6551. These enable a flexibility of color, spatial-frequency content, temporal-frequency content, duration, size, and position that is not provided by most other media. CRTs are, however, not perfect; they suffer from the effects of temporal instability, spatial variability, lack of phosphor constancy, gun interdependence, and gun nonlinearity. This paper describes methods of assessing these aspects of monitor performance with respect to how significant each may be in psychometric terms. Although every application of CRT use in visual psychophysics is different, some general rules can be formulated to help ensure that unwanted effects are kept to a minimum. For the CRT used in this study (Barco CDCT 6551), a warm-up time of 30-45 min is necessary before chromatic and luminous stability ensues. Restriction of individual gun outputs to within 10%-90% of the possible range ensures that the effects of gun interdependence and lack of phosphor constancy are negligible. Calibration methods dealing with the linearization of gun output are also discussed.     

Book reviews

Ohne Zusammenfassung

---

Book reviews

     

Mother-child communication about location: giving and following directions for finding hidden objects

We conducted 2 experiments to examine how mothers structure directions to young children for finding hidden objects and how young children use these directions to guide their searches. In Experiment 1, we examined the reference frames mothers use to communicate with their 2.5-, 3-, and 3.5-year-old children about location by asking mothers to verbally disambiguate a target hiding container from an identical nontarget hiding container. We found that mothers' reference frame use was primarily governed by the relative proximity of the target container to the landmark and themselves. Older children were more successful in following directions than were younger children, and children were more likely to search successfully in response to a person than to a landmark frame of reference. In Experiment 2, we further investigated how 3-year-old children follow directions involving person and landmark frames of reference by asking mothers to use either only themselves or only the landmark to describe the target location. Children in the person reference frame condition successfully followed their mother's directions when the target was relatively close to the mother, but not when the target was relatively far from the mother. Children in the landmark reference frame condition were at chance regardless of the relative proximity of the target to the landmark. The discussion focuses on the roles of spatial proximity and reference frames in mother-child spatial communication.