It is well documented that people are less interested in studying plants than animals. We tested whether university students would selectively recall more animal images than plant images even when equally-nameable plant and animal images were presented for equal lengths of time. Animal and plant images were pre-tested and 14 animal-plant pairs were selected, based on student ability to equally name the images. These images were randomly presented to two groups of university students: those currently enrolled in a psychology class and those currently enrolled in a botany class. Student recall of each image was recorded after a distracting task. The results confirmed that the animal images were recalled significantly more than the plant images. There was no apparent effect of attending a botany class on these results. However, gender effects were identified for recall of plant versus animal images in general (women recalled more plants than men) and for four specific plant images (carnation, rose, daisy, and venus fly trap). When teaching biology, teachers should present equal numbers of plant and animal examples and use the most memorable plant images possible to attempt to offset student selective attention to animals.

We describe a model of neural recoding in spatial vision that specifies how the outputs of selected units akin to VI cells are normalized and combined to signal information about particular stimulus attributes. The recoding portion of the model is linked to psychophysical behavior via a two-stage signal-detection decision module that specifies how the outputs of the combining mechanisms are used in making fine spatial discriminations. We describe how masking and cue summation experiments isolate each of the processing stages, how earlier results from such studies guided development of the model, and we demonstrate how these procedures permit empirical estimates of model parameters as well as tests of alternative formulations. An important part of our work describes the characteristics of two complementary types of higher-level mechanisms isolated from previously published discrimination data. One sums normalized primary-level responses over disparate frequencies to signal precise information about the orientation of a stimulus; the other sums over all orientations to signal the spatial grain of texture-like patterns. We demonstrate how the model accounts for a large body of previously published discrimination data, and present the results of a new quantitative test of model predictions.

The effect of contrast gain control mechanisms on discrimination between highly similar simple and complex stimuli is examined, with a focus on how discrimination accuracy changes as a function of the contrast of stimulus components. Two models of contrast gain control are evaluated. In both, the response of each pathway is attenuated by a factor determined by the total activity in a large pool of pathways. One model bases attenuation on the sum of linear filter responses within this pool; the other, based on Heeger's contrast energy-driven model [J. Neurophysiol. 70, 1985 (1993)], uses squared filter response. Predictions generated from the models are compared with data from experiments reported here and from the literature. Predictions are made for simple grafting stimuli of different sizes and for stimuli to which a second grafting component is added either as a second cue or as a mask. With one exception, predictions of the models agree closely with each other and with the data. The exception is a masking study that differentiates the models and supports the filter-driven model over the energy-driven model.

Spatial interactions among orientation-tuned gain control processes are presumed to mediate center-surround contrast-contrast phenomena. In this paper, we assess contributions of gain control processes that pool over orientation. We measured the apparent contrast of a luminance-modulated center disk embedded in various modulated surrounds. In all conditions, observers compared the apparent contrast of the test center to an identically modulated disk with no surround. When center and surround are simple, vertical sinusoids and presented in phase, suppression depends upon surround contrast and is marked at high contrasts. When components are presented 180 degrees out of phase, no suppression occurs at any contrast. When a horizontal component is added to the surround, much less suppression occurs. However, strong suppression is reinstated when both center and surround are plaids. Neither of the latter two effects are phase dependent. We suggest that two different sources of gain control are revealed by the simple sinusoidal and the plaid stimuli. One is orientation tuned and phase-dependent. The other pools over all orientations and includes neurons tuned to multiple phases.

Many psychophysical experiments generate data that form multidimensional tables of frequencies. Although these tables are conventionally analyzed by such theoretical models as signal-detection theory, a direct and atheoretical analysis of the associations present in the data gives additional valuable information about the underlying detection processes. Direct frequency analysis can investigate quite complicated patterns of association; furthermore, it allows approximate statistical tests of specific hypotheses to be run. Thus, it provides a valuable adjunct to theoretical models.