Diego Antonio De Simone
Istituto di Scienze e Tecnologie della Cognizione, CNR, Roma Dipartimento di Filosofia, Sapienza Università di Roma, Roma
diegoantonio.desimone@gmail.com
Eva Piano Mortari
Istituto di Scienze e Tecnologie della Cognizione, CNR, Roma Dipartimento di Neurobiologia, Sapienza Università di Roma, Roma
eva.pianomortari@gmail.com
Carlo De Lillo
School of Psychology, University of Leicester, Leicester cdl2@leicester.ac.uk
Valentina Truppa
Istituto di Scienze e Tecnologie della Cognizione, CNR, Roma valentina.truppa@istc.cnr.ir
The human visual system shares several neurophysiological mechanisms with many other diurnal primates. One of the main constrains in this common evolutionary history may be the limited amount of information that the Cen- tral Nervous System (CNS) can select and retain for further elaboration. Our
CNS has, in fact, a limited ability to store environmental information in a fairly unprocessed way for some short time after the removal of the stimuli. It has been argued that sensory inputs can be stored as representations in some relatively labile form for several hundred milliseconds at least for visual, au- ditory, and tactile inputs (Baddeley, 1990; Coltheart, 1980). In humans, this form of short-lived persistence of a sensory stimulus in the visual modality has been identified using the delayed partial report procedure by Sperling (1960) and Averbach and Coriell (1961) and subsequently defined as "iconic memory" by Neisser (1967). Building on those results, Atkinson and Shiffrin (1968) proposed the Multi-store Model of Memory, which includes three separate memory stores: Sensory Memory (SM), Short-Term Memory (STM) and Long-Term Memory (LTM). In this model, each store has a different du- ration, capacity and mode of encoding. It has been argued that the temporary permanence of information in SM allows the visual system to select which aspects of the input should be elaborated further before the trace decays (Coltheart et al., 1974). Consequently, Iconic Memory has been considered as a fundamental component of models of human vision. However, despite the ubiquity of this sensory store in models of visual processing, little is known about its physiological basis and how it works in other species. It is reasonable to expect that species with visual systems similar to that of hu- mans, such as nonhuman primate species, should be sensitive to manipula- tions affecting this type of memory.
Comparative studies on the ability to recognize previously observed vis- ual patterns have often employed variations of the Matching-to-Sample (MTS) task (e.g., Buffalo et al., 2000; Fujita, 2009; Galvao et al. 2005, 2008; Nelson and Wasserman, 1978; Mishkin and Delacour, 1975; Oden et al. 1988; Truppa et al. 2010; Vauclair et al., 1993; Washburn et al., 1989; Wright and Delius 2005). In this task, two or more comparison stimuli are presented and participants choose which of them most closely resembles a stimulus presented as the sample. In the simultaneous MTS (SMTS), the sample stimulus remains visible when the comparison stimuli appear. In the delayed matching-to-sample (DMTS), the sample stimulus disappears at the same time as the presentation of the comparison stimuli (0-delay MTS) or a variable time delay can be imposed between the disappearance of the sample and the presentation of the comparison stimuli. When no delays are imposed between the presentation of the sample and the comparison stimuli (either SMTS or 0-delay MTS) participants are not required to code the stimuli in capacity bound memory stores since they would always be available percep- tually either as physical stimuli (SMTS) or possibly as part of high capacity sensory memory (0-delay MTS). By contrast, when a delay is introduced be- tween the disappearance of the sample and the presentation of the compari-
son stimuli (DMTS), the recognition of the matching stimulus must rely on the memory representation of the sample and can prove more or less demand- ing as a function of the delay length. Because DMTS tasks are suitable for testing a variety of species, they can provide important insight into the mech- anisms of visual cognition by allowing meaningful interspecies comparisons. Previous studies using DMTS tasks in nonhuman species have focused main- ly on the assessment of the limits of the retrieval of information stored in short- and long-term memory. However, a thorough investigation of pattern of deterioration of memory at very short delays would be important to carry out to assess the role of rapidly decaying visual memory in pattern recogni- tion.
The present study was aimed at evaluating if visual Matching-to-Sample involves processes facilitating recognition in time frames comparable to those ascribed to sensory memory in humans. We carried out two experi- ments to evaluate the effect of (i) the disappearance of the sample stimulus, and (ii) the introduction of delay intervals between the disappearance of the sample and the presentation of the comparison stimuli. We tested five adults tufted capuchins (Sapajus spp.), two males and three females. All subjects were already familiar with the Simultaneous MTS procedure; however, they had never been tested with a Delayed MTS procedure before. The experi- mental apparatus consisted of a computerised testing station, comprising a PC connected to a 19‖ touchscreen and an automatic food dispenser. E-Prime software was used for the presentation of the stimuli and the recording of the subject‘s response. When the monkey provided the correct response, the food dispenser delivered a 45-mg banana-flavoured pellet. The stimulus set com- prised 192 stimuli. Each stimulus consisted of a white pattern on a black background.
The results demonstrated that the simple disappearance of the sample and the introduction of a delay of 0.5 seconds did not affect capuchins‘ perfor- mance either in terms of accuracy or response time. A delay interval of 1.0 second produced a significant increase in response time but still did not affect recognition accuracy. By contrast, delays of 2 and 3 seconds determined a significant increase in response time and a reduction in recognition accuracy. These findings indicate the existence in capuchin monkeys of sensory memory mechanisms facilitating visual recognition in time frames compara- ble to those reported for humans (0.5-1.0 seconds). Moreover, they suggest the presence of a system that allows a high degree of recognition accuracy for delays up to 1.0 second, albeit with increased response times. Overall, our study on capuchin monkeys suggest that mechanisms supporting the brief storage of detailed visual information in aid of recognition may have emerged relatively early during the evolutionary history of primate species.
References
Atkinson, R.C., Shiffrin, R.M. (1968) Human memory: A proposed system and its control processes. In Spence K.W., Spence J.T. (eds.) Psychology Learn. Motiv., vol. 2, pp. 89 – 195. Academic Press, New York.
Averbach, E., Coriell, A.S. (1961) Short-term memory in vision. Bell. Syst. Tech. J. 40, 309-328.
Baddeley, A. (1990) Human memory. Theory and practice. Lawrence Erlbaum Asso- ciates, London.
Buffalo, E.A., Ramus, S.J., Squire, R.L., Zola, S.M. (2000) Perception and recogni- tion memory in monkeys following lesions of area TE and perirhinal cortex. Learn. Memory. 7, 375-382.
Coltheart, M. (1980) The persistence of vision. Philos. T. Roy. Soc. B. 290, 57-69. Coltheart, M., Lea, C.D., Thompson, K. (1974) In defence of iconic memory. Q. J.
Exp. Psychol. 26, 633-641.
Fujita, K. (2009). Metamemory in tufted capuchin monkeys (Cebus apella). Anim. Cogn. 12, 575-585.
Galvão O.F., Barros R.S., Dos Santos J.R., Brino A.L.F., Brandão S., Lavratti C.M., Dube W.V., McIlvane W.J. (2005) Extent and limits of the matching concept in
Cebus apella: a matter of experimental control? Psychol. Rec. 55, 219-232.
Galvão O.F., Soares-Filho P.S.D., Barros R.S., Souza C.B.A. (2008) Matching-to- sample as a model of symbolic behavior for bio-behavioral investigations. Rev. Neuroscience. 19, 149-156.
Mishkin, M., Delacour, J. (1975) An analysis of short-term visual memory in the monkey. J. Exp. Psychol. Anim. B. 1, 326-334.
Neisser, U. (1967) Cognitive Psychology. Appleton-Century-Crofts, New York. Nelson, K.R., Wasserman, E.A. (1978) Temporal factors influencing the pigeon‘s
successive matching-to-sample performance: sample duration, intertrial interval, and retention interval. J. Exp. Anal. Behav. 30, 153-162.
Oden, D.L., Thompson, R.K.R., Premack, D. (1988) Spontaneous transfer of match- ing by infant chimpanzees (Pan troglodytes). J. Exp. Psychol. Anim. B. 14, 140- 145.
Sperling, G. (1960) The information available in brief visual presentations. Psychol. Monogr. Gen. A. 74, 1-29.
Truppa, V., Garofoli, D., Castorina, G., Piano Mortari, E., Natale, F., Visalberghi, E. (2010) Identity concept learning in matching-to-sample tasks by tufted capuchin monkeys (Cebus apella). Anim. Cogn. 13, 1-14.
Vauclair, J., Fagot, J., Hopkins, W.D. (1993) Rotations of mental images in baboons when the visual input is directed to the left cerebral hemisphere. Psychol. Sci. 2, 99-103.
Washburn, D.A., Hopkins, W.D., Rumbaugh, D.M. (1989) Video-task assessment of learning and memory in macaques (Macaca mulatta): Effects of stimulus move- ment on performance. J. Exp. Psychol. Anim. B. 15, 393-400.
Wright, A.A., Delius, J.D. (2005) Learning processes in matching and oddity: the oddity preference effect and sample reinforcement. J. Exp. Psychol. Anim. B. 31, 425-432.