ABSTRACT
Two experiments employing an identity matching-to-sample procedure were carried out to clarify the factors affecting global-local visual processing of capuchin monkeys (Sapajus spp.) in comparison with humans. In the first experiment, we assessed the relative ability of the two species to discriminate high, medium, or low spatial frequencies (HSFs, MSFs, or LSFs). Then, in a second experiment, we determined if the use of a procedure designed to induce a bias toward attending given spatial frequencies could produce a top-down or selection-history modulation of global-local visual processing in capuchins and humans. In the first experiment, monkeys discriminated better HSFs. By contrast, humans discriminated better MSFs and LSFs. The second experiment showed an effect of SF processing on global-local processing in both species. However, this effect was confined to local trials only and occurred under different conditions in the two species. In monkeys, it occurred following a bias toward attending HSFs, whereas in humans, it occurred following a bias toward attending LSFs. These results provide new information about the relative sensitivity of humans and capuchins to different spatial frequencies in vision. Moreover, they suggest that global-local visual processing can be modulated in both humans and monkeys by processes that are not confined to attending one or the other level of stimulus structure. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
Subject(s)
Sapajus , Animals , Humans , Cebus , Visual PerceptionABSTRACT
Using a Matching-To-Sample (MTS) procedure we assessed the effects of stimulus redundancy, defined on the basis of the information-theory approach to shape goodness proposed by Garner (1974) [20], and grouping on the processing of hierarchical visual patterns in capuchin monkeys and humans. In a first experiment, the MTS performance of both capuchin monkeys and humans benefitted from stimulus redundancy. Moreover, a local advantage in capuchins was observed with visual patterns that required grouping at both global and local level. In a second experiment we eliminated the requirement to group at the local level. This was done to determine if the effects of redundancy would have been evident in condition more similar to those used in previous studies of global-local processing in a comparative context. The benefits of stimulus redundancy emerged again in both species but were confined to local processing in monkeys and to global processing in humans. A local advantage was observed in both species. In a third experiment, the reduction of the size of the stimuli and the increase of the quantity of the local elements produced a shift to global dominance in humans but the local dominance in monkeys was preserved. The implications of these results are discussed in relation to other similarities and differences in higher visual functions in humans and monkeys.
Subject(s)
Discrimination Learning , Pattern Recognition, Visual , Visual Perception , Adolescent , Adult , Animals , Cebus , Female , Humans , Male , Photic Stimulation/methods , Psychomotor Performance , Reaction Time , Species SpecificityABSTRACT
Humans show a global advantage when processing hierarchical visual patterns, and they detect the global level of stimulus structure more accurately and faster than the local level in several stimulus contexts. By contrast, capuchins (Cebus apella) and other monkey species show a strong local advantage. A key factor which, if manipulated, could cause an inversion of this effect in monkeys is still to be found. In this study, we examined whether it was possible to induce attention allocation to global and local levels of perceptual analysis in capuchin monkeys and if by doing so, their local dominance could be reversed. We manipulated attentional bias using a matching-to-sample (MTS) task where the proportion of trials requiring global and local processing varied between conditions. The monkeys were compared with humans tested with the same paradigm. Monkeys showed a local advantage in the local bias condition but a global advantage in the global bias condition. The role of attention in processing was confined to the local trials in a first phase of testing but extended to both local and global trials in the course of task practice. Humans exhibited an overall global dominance and an effect of attentional bias on the speed of processing of the global and local level of the stimuli. These results indicate a role for attention in the processing of hierarchical stimuli in monkeys and are discussed in relation to the extent to which they can explain the differences between capuchin monkeys and humans observed in this and other studies.
