The ability of a preexposed (latently inhibited) conditioned stimulus (CS) to serve as (a) a blocker or (b) a second-order reinforcer in Pavlovian fear conditioning was tested in albino rats. Experiment 1 found that a preexposed CS was weakened in its ability to serve as a blocker. Experiment 2 found that a preexposed CS was weakened in its ability to serve as a reinforcer for second-order conditioning (SOC). Experiment 3 found that a 28-day retention interval between the last trial of element conditioning and the first trial of the SOC test did not enhance the ability of the preexposed CS to serve as a reinforcer for SOC, even though it did enhance the ability of that preexposed CS to evoke a first-order conditioned response. Experiment 4 was undertaken in an effort to show a contextually dependent attenuation of LI by employing a context shift between preexposure and element training. However, no attenuation of LI was found. Experiment 5 successfully demonstrated an attenuation of LI by reducing familiarity with the preexposure context prior to CS preexposure, reducing the amount of CS preexposure, and by using 100% reinforcement of the target CS during the first two days of the element training phase. Experiment 6 found that conducting stimulus preexposure and the test for blocking in different contexts did not enhance the ability of a preexposed CS to block conditioning to a neutral CS. Results are interpreted as supporting a learning-deficit view of latent inhibition.

Three experiments are presented that investigated the effects of distracting information on the processing of stimuli for younger and older adults. The first two experiments were controlled laboratory experiments, in which the flanker paradigm was used to investigate whether older and younger adults were affected differently by response compatible or incompatible information. Typically performance measures indicate better performance in terms of reaction times if distracting information is response compatible and reduced performance if distracting information is incompatible with a response to be executed. As an additional variable, the stimulus-to-response mapping was manipulated to investigate whether younger but not older adults were able to reduce the influence of interfering information. The stimulus-to-response mapping was either consistent or varied, and it was assumed that varied but not consistent mapping allowed subjects to reduce the interfering effects of response-incompatible information. The data in the first experiment indicated no differences between younger and older adults. However, the data in the second experiment showed that younger but not older adults were able to reduce the processing of irrelevant information. A reduction of interference in the varied mapping condition could be observed only for younger but not for older adults. Subsequently, the results of these experiments were modeled by means of a connectionist network. The test of the network using linear regression indicated a good fit between the model and the empirical data, separated by each age group, indicating the appropriateness of the theoretical assumptions of the model. The third experiment investigated the effect of compatibility using realistic stimuli, i.e., traffic signals and signs, in order to determine how compatibility governs performance in a more applied setting. No specific age-related performance deficits were observed, however, both age groups benefited from compatible information. This allowed us to derive recommendations for the design of traffic signals and signs.

A person's ability to see an object clearly is based on both the optical characteristics of their eyes and their ability to keep their eyes oriented toward the target. The ability to accomplish the latter can be compromised by self-motion if adequate compensation for the movement is not provided. The goal of the research presented here is to measure subjects' visual acuity during gaze tasks performed while walking. In addition, the effects of body movements on the gaze goals will be quantified using a measure of head fixation distance (HFD). By defining the distance between the subject and a point in space where minimal ocular compensation would be required, HFD provides a goal-relative measure that captures the integrated contributions from all non-ocular body movements. In Study I, subjects walked on a treadmill at 1.8 m/s and fixed their gaze on visual targets placed in front of them at 0.5 and 4 meters. During the "far" target condition, visual acuity was not different between standing and walking. Shorter HFDs during the "near" condition indicate changes in the coordinative relationships of non-ocular body movements. Although these changes appear to facilitate gaze stabilization by reducing the amplitude of the required eye movements, subjects' acuity was compromised while viewing the "near" target during locomotion. In Study II, treadmill speeds from 1.0 to 1.8 m/s were used to investigate the effects of walking velocity on gaze stabilization of the "near" target. Vertical HFD indicated that head pitch was compensating for more of the vertical trunk translation as walking velocity increased, yet visual acuity became progressively worse. In Study III, the "far" target condition from Study I was repeated to investigate visual acuity and vertical HFD at a sub-step timescale. The vertical HFD was shown to vary within the step-cycle and when compared to an assessment made mid-way between heelstrikes, visual acuity was shown to be compromised immediately following heel contact. The results from these experiments indicate that non-ocular mechanisms contribute to gaze stabilization while walking and provide evidence that ocular control is likely more complex than that provided by simple fixed-gain responses to vestibular stimulation.

The main objective of this dissertation was to characterize the tool-using ability of rhesus monkeys and children by examining the acquisition and comprehension of tool-using behavior, and by identifying factors that might be related to individual differences in the ability to use tools. The first study examined whether twenty rhesus monkeys could use a rake to extend reach, whether they understood the required properties of the tool, and whether tool-using ability was correlated with behavioral characteristics. Fifteen monkeys used the rake to retrieve treats placed out-of-reach; however, none of the monkeys tested selected an effective rake from an ineffective rake. The level of tactile oral exploration in non-tool-using contexts was positively correlated with the number of rewards retrieved. The second study examined whether rhesus monkeys could use a rod to insert and probe and whether they understood the effects of using the tool. Only two monkeys used a rod to push a reward out of a clear tube. Subsequent manipulations involving multi-tube combinations, in which only one tube was baited, indicated that the monkeys were unable to select the correct path or tube. However, these monkeys correctly selected the baited tube over empty tubes when the tubes were presented on separate walls. The third study examined whether rhesus monkeys and 36-month-old children were able to use two different tools in series to retrieve a desired object. Both of the two monkeys tested used a rake to retrieve a rod and then used the rod to push a reward out of a clear tube, and all but one of the children tested used the tools in series either on their own or following hints or demonstrations. The fourth study revealed that certain types of object manipulation and behavior were related to tool-using ability in monkeys. In summary, this dissertation characterized tool-using in rhesus monkeys and children, validated new procedures for assessing comprehension in tool-using tasks, and identified certain factors related to individual differences in tool-using ability. The implications of these results are discussed.

The goal of this dissertation was to test the hypothesis that great apes can solve both visible and invisible displacements, whereas monkeys can solve only visible displacements. First, rhesus monkeys, squirrel monkeys, and orangutans received visible and invisible displacement tests that correspond to Stages 4, 5, and 6 of object permanence. Monkeys and orangutans were successful on the visible displacement tests. Most orangutans were successful on all invisible displacement tests except the double displacements. The monkeys were not successful on invisible displacement tests and they had a location preference. Subsequent testing revealed that (1) rhesus monkeys eventually solved single and control invisible displacements, (2) two rhesus monkeys eventually solved double displacements, (3) using a familiar containment device improved performance on invisible displacements and (4) most orangutans eventually solved double invisible displacements when the object was concealed in a cup. In the second part of the dissertation, I determined if poorer performance on invisible displacements was related to increased memory requirement. The primates received three types of problems that had equivalent memory requirement. On Invisible transfer problems, the object was hidden in a box and then invisibly transferred to another box, whereas on Visible transfer problems the object was visibly transferred, and on No transfer problems, it was not transferred. The rhesus monkeys and the squirrel monkeys solved the Visible and the No transfer problems. Only one monkey was successful on the Invisible transfer problems. Given that all problems had equivalent memory requirements, this variable cannot account for poorer performance on Invisible transfer problems. Most orangutans solved all three types of problems. Nevertheless, the performance of the orangutans on Invisible transfer problems was poorer than that on the other problems. Next, cueing sessions were instituted during which a clear box was used in order to allow the primates to see if and how the object was transferred. Then, the primates were re-tested on the three problems. Cuing helped monkeys and orangutans find the object on Invisible transfer problems. In summary, the results of this dissertation indicated that overall, the orangutans outperformed the monkeys on invisible displacements. However, a few orangutans performed as poorly as the monkeys on invisible displacements, and a few monkeys performed as well as the orangutans. Thus, individual differences must be taken into account to adequately portray the distribution of object permanence skills in non-human primates.

Object-oriented behavior requires the fine interplay between perception and action. Two visuomotor cortical channels are typically implicated in grasping. One is described as specifically sensitive to extrinsic object parameters (e.g., location). The other is described as specifically sensitive to intrinsic object parameters (e.g., shape). According to Jeannerod (1981), the first, dorsal, channel directs the arm transport component of a grasp, while the second, ventral, channel directs the object manipulation component of a grasp. The role of both types of object information in planning a grasp is examined. Specifically, questions directed at the degree of planning by each component, their independence from one another, as well as their mode of planning (serial vs. parallel) are addressed. Two experiments employed a precueing paradigm to manipulate the type of information available prior to movement onset. Variables examined were the location of an object (left/right), its shape (sphere/dowel), as well as its distance from the hand. The primary measure of interest was reaction time to a "go" signal. The kinematics of the ensuing movements were also analyzed. Sizable reaction time costs were found when either type of information was precued ambiguously or incorrectly. Such costs illustrate that both extrinsic and intrinsic object parameters are critical for planning a grasp, supporting the active participation of both components in planning. The overall pattern of reaction time results implies that the arm transport channel is responsible for 'sketching out' an overall plan of action upon which the plan for object manipulation 'rides.' The absence of an interaction between extrinsic and intrinsic parameters, furthermore, suggests that the two channels are functionally independent. The additive effects of extrinsic and intrinsic parameters, finally, is evidence for a serial mode of planning by the two channels. The kinematics of the movements support findings from the literature, and suggest that movements are not time-scaled variations of a prototypical movement. They also reveal that the arm transport component of the movement is affected by both extrinsic and intrinsic object properties; the object manipulation component, on the other hand, appears only sensitive to intrinsic object properties.

The primary goal of this study is to develop a theory of the processing of doubly-quantified sentences such as A squirrel picked up every nut, particularly how the scope ambiguity in such sentences is resolved. The research departs from most psycholinguistic work in drawing upon current linguistic theories of LF, the syntax-semantics interface, and formal semantics. First, I investigate the issue of how structural factors affect quantifier scope preferences. I argue that the processor takes an economic stance towards scope assignment. The preferred relative scoping of two quantified phrases is computed from the 'required' LF structure--the LF constructed from required grammatical operations acting on S-structure. Furthermore, I contend that when every has scope over a, the processor does not commit to how many entities the a-phrase represents. Next, I present an analysis of the semantic differences between each and every with respect to event distributivity, in preparation for considering the scope behavior of these quantifiers. I demonstrate that a sentence containing each can only be true of an event which has a totally distributive event structure, where each individual object in the restrictor set of the quantified phrase is associated with its own subevent, and all the subevents are differentiated on some relevant dimension. Every is subject to the weaker requirement that there be at least two different subevents. Finally, I apply the semantic analysis of each and every to the question of how individual quantifiers affect scope preferences. Each has often been said to have a stronger preference for wide scope than every. I argue that this observation arises from cases where each takes wide scope in order to fulfill its condition requiring total event distributivity and differentiation of subevents. Otherwise the scope behavior of each and every is quite similar; they preferentially take wide scope only when that is the scoping computed off the required LF structure. More generally, I hypothesize that a quantifier's scope behavior is driven by the lexical condition(s) which are part of its meaning. Experimental evidence is presented in support of each of these claims.

The following four eye movement experiments examined the hypothesis that sentence context has a similar effect on words with higher frequency neighbors and lexically ambiguous words. This would be consistent with the notion that lexically ambiguous words can be thought of as extreme examples of word neighbors (word roommates). Experiment 1 presented words with higher frequency neighbors (birch, birth) in sentences that provided either a neutral context (i.e., the target word and its higher frequency neighbor could both fit equally well into the sentence) or biased context (i.e., the target word was a better fit than its higher frequency neighbor). Experiment 2 used the items from Experiment 1 with a group of elderly readers (65 years of age or older) to investigate age related differences in the neighbor frequency effect. A prior study by Rayner, Reichle, Stroud, Williams & Pollatsek (2006) concluded that elderly readers adopt a riskier reading strategy that relies heavily on partial parafoveal information. Therefore, elderly readers may be more likely to miscode words that have higher frequency neighbors. Experiment 3 examined the role that syntax plays in the neighbor frequency effect during reading. Prior research by Folk and Morris (2003) using ambiguous word stimuli that spanned syntactic category suggests that syntax can mediate the meaning resolution process. A critical difference between lexically ambiguous words and the words used in experiments 1-3 is that the two meanings of lexically ambiguous words have the phonological code. Therefore, Experiment 4 used words that are homonyms with their higher frequency neighbor (beech, beach).

No description available.

This study assessed the effectiveness of pavement markings painted along the curbs of a two-lane street on reducing driving speed around a curve. Three different types of marking patterns were investigated in a single-case design. The velocity and perceived speed of vehicles passing through a frequently used entrance road on a university campus were measured. Velocity was measured by recording the time it took vehicles to travel 150 ft (45.7 m). To measure perceived speed, volunteer observers rated the speed of videotaped vehicles using a 15 item questionnaire developed for this study. Data were collected only on passenger vehicles during clear weather conditions. The velocity measure indicated that markings, particularly those in a checkerboard pattern, were effective in reducing the number of drivers exceeding 35 mph. This outcome is consistent with the findings from previous studies with similar interventions. The perceived speed measure did not show meaningful trends across phases. Future research with this type of inexpensive intervention and the need to develop a valid and reliable measure of perceived speed, which takes into consideration safety factors in assessing driving behavior, is discussed.