Martha J. Farah

Parts and wholes in face recognition

Are faces recognized using more holistic representations than other types of stimuli? Taking holistic representation to mean representation without an internal part structure, we interpret the available evidence on this issue and then design new empirical tests. Based on previous research, we reasoned that if a portion of an object corresponds to an explicitly represented part in a hierarchical visual representation, then when that portion is presented in isolation it will be identified relatively more easily than if it did not have the status of an explicitly represented part. The hypothesis that face recognition is holistic therefore predicts that a part of a face will be disproportionately more easily recognized in the whole face than as an isolated part, relative to recognition of the parts and wholes of other kinds of stimuli. This prediction was borne out in three experiments: subjects were more accurate at identifying the parts of faces, presented in the whole object, than they were at identifying the same part presented in isolation, even though both parts and wholes were tested in a forced-choice format and the whole faces differed only by one part. In contrast, three other types of stimuli–-scrambled faces, inverted faces, and houses–-did not show this advantage for part identification in whole object recognition.

Socioeconomic status and the developing brain

Childhood socioeconomic status (SES) is associated with cognitive achievement throughout life. How does SES relate to brain development, and what are the mechanisms by which SES might exert its influence? We review studies in which behavioral, electrophysiological and neuroimaging methods have been used to characterize SES disparities in neurocognitive function. These studies indicate that SES is an important predictor of neurocognitive performance, particularly of language and executive function, and that SES differences are found in neural processing even when performance levels are equal. Implications for basic cognitive neuroscience and for understanding and ameliorating the problems related to childhood poverty are discussed.

A computational model of semantic memory impairment : modality specificity and emergent category specificity

It is demonstrated how a modality-specific semantic memory system can account for category-specific impairments after brain damage. In Experiment 1, the hypothesis that visual and functional knowledge play different roles in the representation of living things and nonliving things is tested and confirmed. A parallel distributed processing model of semantic memory in which knowledge is subdivided by modality into visual and functional components is described. In Experiment 2, the model is lesioned, and it is confirmed that damage to visual semantics primarily impairs knowledge of living things, and damage to functional semantics primarily impairs knowledge of nonliving things. In Experiment 3, it is demonstrated that the model accounts naturally for a finding that had appeared problematic for a modality-specific architecture, namely, impaired retrieval of functional knowledge about living things. Finally, in Experiment 4, it is shown how the model can account for a recent observation of impaired knowledge of living things only when knowledge is probed verbally.

Socioeconomic status and the brain: mechanistic insights from human and animal research

Human brain development occurs within a socioeconomic context and childhood socioeconomic status (SES) influences neural development — particularly of the systems that subserve language and executive function. Research in humans and in animal models has implicated prenatal factors, parent–child interactions and cognitive stimulation in the home environment in the effects of SES on neural development. These findings provide a unique opportunity for understanding how environmental factors can lead to individual differences in brain development, and for improving the programmes and policies that are designed to alleviate SES-related disparities in mental health and academic achievement.

Childhood poverty: specific associations with neurocognitive development.

Growing up in poverty is associated with reduced cognitive achievement as measured by standardized intelligence tests, but little is known about the underlying neurocognitive systems responsible for this effect. We administered a battery of tasks designed to tax-specific neurocognitive systems to healthy low and middle SES children screened for medical history and matched for age, gender and ethnicity. Higher SES was associated with better performance on the tasks, as expected, but the SES disparity was significantly nonuniform across neurocognitive systems. Pronounced differences were found in Left perisylvian/Language and Medial temporal/Memory systems, along with significant differences in Lateral/Prefrontal/Working memory and Anterior cingulate/Cognitive control and smaller, nonsignificant differences in Occipitotemporal/Pattern vision and Parietal/Spatial cognition.

Neurocognitive enhancement: what can we do and what should we do?

Our growing ability to alter brain function can be used to enhance the mental processes of normal individuals as well as to treat mental dysfunction in people who are ill. The prospect of neurocognitive enhancement raises many issues about what is safe, fair and otherwise morally acceptable. This article resulted from a meeting on neurocognitive enhancement that was held by the authors. Our goal is to review the state of the art in neurocognitive enhancement, its attendant social and ethical problems, and the ways in which society can address these problems.

Visual and spatial mental imagery: Dissociable systems of representation

Abstract We argue that the debate over whether mental images are visual or spatial representations is based on the false premise that they must be one or the other. In support of the hypothesis that mental imagery has distinct visual and spatial components of representation, we (1) point out a correspondence between the notions of visual appearance and spatial location representations in visual neurophysiology, on the one hand, and the notions of visual and spatial representations as used in the debate about mental imagery, on the other; and (2) present the performance of a brain-damaged patient with impaired visual appearance representations on a variety of tasks used by cognitive psychologists on one side or other of the visual vs spatial imagery debate. The patient is severely impaired on tasks previously used to argue for the visual nature of imagery, but performs normally on tasks previously used to argue for the spatial nature of imagery. This implies that the two groups of tasks tap distinct types of representation, which are neurologically dissociable and hence comprise functionally independent subsystems of imagery representation.

Does visual attention select objects or locations

Much research supports location-based attentional selection, but J. Duncan (1984) presented data favoring object-based selection in a shape discrimination task. Does attention select objects or locations? We confirmed that Duncans task elicits selection from spatially invariant object representations rather than from a grouped location-based representation. We next asked whether this finding was due to location-based filtering; the results again supported object-based selection. Finally, we demonstrated that when Duncans objects were used in a cued detection task the results were consistent with location-based selection. These results suggest that there may not be a single attention mechanism, consistent with Duncans original claim that object-based and location-based attentional selection are not mutually exclusive. Rather, attentional limitations may depend on the type of stimulus representation used in performing a given task.

The neurological basis of mental imagery: A componential analysis

Abstract The neurological literature contains numerous reports of loss of mental imagery following brain damage. This paper represents an attempt to interpret the patterns of deficits and preserved abilities in these reports in terms of a componential information-processing model of imagery. The principal result was a consistent pattern of deficit in a subset of patients, which could be attributed to a loss of the image generation component of imagery; examination of the lesion sites in this subset of patients implicated a region in the posterior left hemispheres as critical for the image generation process. The analysis also provided evidence that the long-term visual memories used in imagery are also used in recognition, and that dreaming and waking visual imagery share some underlying processes.

Is Visual Imagery Really Visual? Overlooked Evidence from Neuropsychology.

Does visual imagery engage some of the same representations used in visual perception? The evidence collected by cognitive psychologists in support of this claim has been challenged by three types of alternative explanation: Tacit knowledge, according to which subjects use nonvisual representations to simulate the use of visual representations during imagery tasks, guided by their tacit knowledge of their visual systems; experimenter expectancy, according to which the data implicating shared representations for imagery and perception is an artifact of experimenter expectancies; and nonvisual spatial representation, according to which imagery representations are partially similar to visual representations in the way they code spatial relations but are not visual representations. This article reviews previously overlooked neuropsychological evidence on the relation between imagery and perception, and discusses its relative immunity to the foregoing alternative explanations. This evidence includes electrophysiological and cerebral blood flow studies localizing brain activity during imagery to cortical visual areas, and parallels between the selective effects of brain damage on visual perception and imagery. Because these findings cannot be accounted for in the same way as traditional cognitive data using the alternative explanations listed earlier, they can play a decisive role in answering the title question.