Paulo Roney Kilpp Goulart

A note on select- and reject-controlling relations in the simple discrimination of capuchin monkeys (Cebus apella)

Controlling relations in the simple discrimination performances of capuchin monkeys (Cebus apella) were studied in two experiments using a blank-comparison procedure. The main goal was to determine whether monkeys would (a) select an S+ stimulus if another stimulus was substituted for the S- (indicating a select-controlling relation) and (b) reject an S- if another stimulus was substituted for S+ (indicating a reject-controlling relation). In experiment 1, two simple simultaneous discriminations were established, one of which was reversed repeatedly until rapid reversal learning was exhibited. During subsequent probe tests, some behavior was consistent with select- and reject-controlling relations, but there was also substantial variability. To control the variability, the procedures of experiment 2 were designed to establish select- and reject-control relations directly by training with the blank-comparison procedure. On subsequent probe trials, new stimuli were substituted for the blank comparison. Both animals exhibited consistent, reliable select- and reject-controlling relations. These experiments are the first to employ the blank-comparison procedure with non-human subjects. They also demonstrate a reliable method for generating select- and reject-controlling relations for experimental study.

Testes de identidade generalizada com objetos em macaco-prego (Cebus apella)

Capuchin monkeys show generalized identity (GI) when tests are preceded by repeated shifts of simple discrimination training (RSSD) with stimuli used in tests. The present study evaluated if that facilitating effect of RSSD training could be due exclusively to the previous contact with the testing stimuli. It was given to a male capuchin monkey four GI tests with objects: Test 1 - an identity conditional discrimination task with new stimuli; Test 2 - with the same stimuli used in Test 1 after RSSD training to induce conditional control; Test 3 - with new stimuli, freely manipulated by the subject previously; and Test 4 - with the same stimuli used in Test 3 after RSSD training. The subjects performance reached the learning criterion in Tests 2 and 4. RSSD training was more effective than free manipulation to produce immediate matching to sample with new stimuli.

A novel nonsense mutation in the tyrosinase gene is related to the albinism in a capuchin monkey (Sapajus apella)

BackgroundOculocutaneous Albinism (OCA) is an autosomal recessive inherited condition that affects the pigmentation of eyes, hair and skin. The OCA phenotype may be caused by mutations in the tyrosinase gene (TYR), which expresses the tyrosinase enzyme and has an important role in the synthesis of melanin pigment. The aim of this study was to identify the genetic mutation responsible for the albinism in a captive capuchin monkey, and to describe the TYR gene of normal phenotype individuals. In addition, we identified the subject’s species.ResultsA homozygous nonsense mutation was identified in exon 1 of the TYR gene, with the substitution of a cytosine for a thymine nucleotide (C64T) at codon 22, leading to a premature stop codon (R22X) in the albino robust capuchin monkey. The albino and five non-albino robust capuchin monkeys were identified as Sapajus apella, based on phylogenetic analyses, pelage pattern and geographic provenance. One individual was identified as S. macrocephalus.ConclusionWe conclude that the point mutation C64T in the TYR gene is responsible for the OCA1 albino phenotype in the capuchin monkey, classified as Sapajus apella.

Reduced Discrimination in the Tritanopic Confusion Line for Congenital Color Deficiency Adults

In congenital color blindness the red–green discrimination is impaired resulting in an increased confusion between those colors with yellow. Our post-receptoral physiological mechanisms are organized in two pathways for color perception, a red–green (protanopic and deuteranopic) and a blue–yellow (tritanopic). We argue that the discrimination losses in the yellow area in congenital color vision deficiency subjects could generate a subtle loss of discriminability in the tritanopic channel considering discrepancies with yellow perception. We measured color discrimination thresholds for blue and yellow of tritanopic channel in congenital color deficiency subjects. Chromaticity thresholds were measured around a white background (0.1977 u′, 0.4689 v′ in the CIE 1976) consisting of a blue–white and white–yellow thresholds in a tritanopic color confusion line of 21 congenital colorblindness subjects (mean age = 27.7; SD = 5.6 years; 14 deuteranomalous and 7 protanomalous) and of 82 (mean age = 25.1; SD = 3.7 years) normal color vision subjects. Significant increase in the whole tritanopic axis was found for both deuteranomalous and protanomalous subjects compared to controls for the blue–white (F2,100 = 18.80; p < 0.0001) and white–yellow (F2,100 = 22.10; p < 0.0001) thresholds. A Principal Component Analysis (PCA) found a weighting toward to the yellow thresholds induced by deuteranomalous subjects. In conclusion, the discrimination in the tritanopic color confusion axis is significantly reduced in congenital color vision deficiency compared to normal subjects. Since yellow discrimination was impaired the balance of the blue–yellow channels is impaired justifying the increased thresholds found for blue–white discrimination. The weighting toward the yellow region of the color space with the deuteranomalous contributing to that perceptual distortion is discussed in terms of physiological mechanisms.

Simple discrimination by exclusion in infant capuchin monkeys.

Learning by exclusion in capuchin monkeys is reported. Two infant female capuchin monkeys were tested for control of choices by exclusion and by novelty and for incorporation of novel stimuli into functional classes after establishment of a robust baseline for exclusion in a 2-choice simultaneous simple discrimination task including 4 positive and 4 negative stimuli. Control by exclusion was assessed by substituting novel stimuli for familiar baseline positive stimuli, resulting in 16 stimulus pairs of combinations of 4 novel stimuli and 4 negative stimuli. Control by novelty was assessed by replacing new stimuli for baseline negative stimuli while maintaining the positive stimuli from the exclusion phase. Finally, the learning of new simple discriminations by exclusion was assessed by replacing novel stimuli with the 4 familiar negative stimuli used in the previous exclusion test. Both subjects demonstrated control by exclusion but not by novelty. One subject learned new stimulus functions without errors after exposure to very few training trials in the exclusion context, consistent with the “fast mapping” phenomenon.