Why are there eccentricity effects in visual search? Visual and attentional hypotheses

In standard visual search experiments, observers search for a target item among distracting items. The locations of target items are generally random within the display and ignored as a factor in data analysis. Previous work has shown that targets presented near fixation are, in fact, found more efficiently than are targets presented at more peripheral locations. This paper proposes that the primary cause of this “eccentricity effect” (Carrasco, Evert, Chang, & Katz, 1995) is an attentional bias that allocates attention preferentially to central items. The first four experiments dealt with the possibility that visual, and not attentional, factors underlie the eccentricity effect. They showed that the eccentricity effect cannot be accounted for by the peripheral reduction in visual sensitivity, peripheral crowding, or cortical magnification. Experiment 5 tested the attention allocation model and also showed that RT X set size effects can be independent of eccentricity effects. Experiment 6 showed that the effective set size in a search task depends, in part, on the eccentricity of the target because observers search from fixation outward.     

The Relation of ERP Components to Complex Memory Processing

The relation between various ERP components generated during encoding of a word and its subsequent recall were investigated using a “rote” serial-order and an “elaborative” category memory task. Words (flashed separately) were time-locked to EEG recordings from 21 cortical sites. ERP components from the five subjects having the highest recall scores were compared to the five lowest scoring subjects. Results based on the P200 peak amplitude data as well as the N400 and late positive component peak amplitude and latency data suggest that anterior and posterior distributional differences are elicited during encoding of words for rote and elaborative memory tasks. Furthermore, strong individual differences in these patterns were found as a function of task. A tentative argument was made that the obtained anterior and posterior differences may index different word feature selection and encoding processes, which are differentially utilized by high and low recallers.     

Prehension movements and perceived object depth structure

This study asked the question, “Will the motor pattern to a perceived two-dimensional (2-D) object differ from that same object when it is perceived as three dimensional (3-D)?” Subjects were required to reach and grasp an apple that could appear to be 2-D or 3-D. Two experimental sessions were conducted. In Condition A, the apple was initially perceived to be 2-D, but, for 20% of trials, it suddenly shifted to a 3-D apple at movement onset. In Condition B, the apple was initially perceived to be 3-D, but, for 20% of trials, it suddenly shifted to a 2-D silhouette of the same apple. For control trials, subjects grasped the perceived 2-D apple as if it were a disc (82%), and they grasped the 3-D apple, as they would a normal apple, with a whole-hand grasp (86%). For Condition A perturbed trials, there was a rapid change from a 2-D precision grip to a 3-D whole-hand prehension, whereas the converse was true for the opposite perturbation. Peak acceleration was anticipated for Condition A perturbed trials but not for Condition B perturbed trials. These results indicate that the motor patterns we use in interacting with an object are strongly influenced by the way we perceive the object in real time, and that object affordances, such as dimension, can override the influence exerted by existing representations.     

ARTICULATION TRAINING OF TWO HEARING-IMPAIRED GIRLS1

Two 4-yr-old hearing-impaired girls were trained to articulate correctly /f/ and /sh/ phonemes in the initial position of words in response to pictures. They were first trained to imitate, and then to respond on demand of “what's this?” As a result, both girls generalized correct articulation to words requiring both phonemes in the initial and final positions.     

The definition of sex stereotypes via the adjective check list

The Adjective Check List (ACL) was employed in the empirical definition of male and female stereotypes by 50 male and 50 female college student subjects. Judgments by male and female subjects correlated highly. There were 33 male adjectives and 30 female adjectives on which at least 75% of both sexes agreed. With a 60% agreement criterion, there were 98 male and 83 female adjectives. Both male and female stereotypes were treated as hypothetical persons and were shown to be highly deviant on standard ACL norms, with the male stereotype being more deviant and perhaps more “disturbed” than the female stereotype. It was concluded that the ACL is a promising method for the definition and study of sex stereotypes.     

The effect of continuous, intermittent, and "placebo" reinforcement on the effectiveness of the conditioning treatment for enuresis nocturna

It has been suggested that intermittent reinforcement may be of value in reducing the rate of relapse in bedwetting conditioning therapy. An experiment was conducted with 30 enuretic boys to examine acquisition and extinction parameters of continuous (100%), intermittent (70% variable ratio), and “placebo” (0%) reinforcement schedules. Reinforced trials were administered as in the typical Mowrer conditioning procedure. Non-reinforced trials were achieved by means of a time delay with the subsequent alarm being activated in the parent's room rather than in the child's room. These procedures required the development of a new conditioning device which could be programmed to automatically administer the desired schedule of reinforcement. The results of the field investigation revealed that continuous reinforcement (CR) and intermittent reinforcement (IR) groups attained acquisition in approximately the same number of trials and with essentially the same success rate. Relapse rate was significantly greater in the CR group than in the IR group. The placebo group showed no improvement over the 6 weeks of treatment. The results of this study may be interpreted as supporting the tenet that relapse can be viewed and treated as an extinction of the acquired response.     

Teaching a complex verbal response to a hearing-impaired girl

A 3-yr-old hearing-impaired girl, who used neither the article "the" nor the auxiliary verb "is" was taught to use these words in describing a picture, initially through imitation and then in response to the command, "Tell me about this". As a result, she was able to use sentences in the present progressive form to describe a number of pictures on which she had received no training. This newly acquired behavior was subsequently extinguished and then reinstated.     

Order effects in Rokeach's Value Survey

Two-hundred-twelve sociology students completed a version of Rokeach's Value Survey in which the presentation order of the values was randomized. Each respondent received a unique randomization pattern. Spearman's correlations were computed between the presentation order and the order of ranking done by the respondent. The magnitude of the correlations obtained was such that the amount of bias created by presentation order was sufficiently small as to suggest that order effects are not a problem in the instrument.