2022
Ratcliff, R. & McKoon, G. (2022). Can neuropsychological testing be improved with model-based approaches? Trends in Cognitive Science, 11, 899-901.
2021
Ratcliff, R., Scharre, D.W., & McKoon, G. (2021). Discriminating memory disordered patients from controls using diffusion model parameters from recognition memory. Journal of Experimental Psychology: General. 151(6), 1377–1393.
2020
Huang-Pollock, C., Ratcliff, R., McKoon, G., Roul, A., Warner, T., Feldman, J., & Wise, S. (2020). A diffusion model analysis of sustained attention in children with ADHD. Neuropsychology, 34, 641-653.
Ratcliff, R., & McKoon, G. (2020). Decision making in numeracy tasks with spatially continuous scales. Cognitive Psychology, 116, e-pub ahead of print.
Ratcliff, R. & McKoon, G. (2020). Examining aging and numerosity using an integrated diffusion model. Journal of Experimental Psychology: Learning, Memory, and Cognition, 46, 2128-2152.
2018
McKoon, G., & Ratcliff, R. (2018). Adults with poor reading skills, older adults, and college students: The meanings they understand during reading using a diffusion model analysis. Journal of Memory and Language, 102, 115-129.
Ratcliff, R., Huang-Pollock, C., & McKoon, G. (2018). Modeling individual differences in the go/no-go task with a diffusion model. Decision, 5, 42-62.
Ratcliff, R., & McKoon, G. (2018). Modeling numeracy representation with an integrated diffusion model. Psychological Review, 125, 183-217.
Ratcliff, R., Voskuilen, C., & McKoon, G. (2018). Internal and external sources of variability in perceptual decision-making. Psychological Review, 125, 33-46.
Voskuilen, C., Ratcliff, R., & McKoon, G. (2018). Aging and confidence judgments in item recognition. Journal of Experimental Psychology: Learning, Memory, and Cognition, 44, 1-23.
2017
Huang-Pollock, C., Ratcliff, R., McKoon, G., Shapiro, Z., Weigard, A., & Galloway-Long, H. (2017). Using the diffusion model to explain cognitive deficits in Attention Deficit Hyperactivity Disorder. Journal of Abnormal Child Psychology, 45(1), 57-68.
McKoon, G., & Ratcliff, R. (2017). Adults with poor reading skills and the inferences they make during reading. Scientific Studies of Reading, 21, 292-309.
Voskuilen, C., Ratcliff, R., Fennell, A., & McKoon, G. (2017). Diffusion models of memory and decision making. In Wixted, J.T. (Ed.), Cognitive Psychology of Memory, Vol.2 of Learning and Memory: A Comprehensive Reference, 2nd Edition, Byrne, J.D. (Ed.), pp. 227-241. Oxford: Academic Press.
2016
McKoon, G. & Ratcliff, R. (2016). Adults with poor reading skills: How lexical knowledge interacts with scores on standardized reading comprehension tests. Cognition, 146, 453-469.
Ratcliff, R., Smith, P.L., Brown, S.D., & McKoon, G. (2016). Diffusion decision model: Current issues and history. Trends in Cognitive Science, 20, 260-281.
Thompson, C.A., Ratcliff, R., & McKoon, G. (2016). Individual differences in the components of children’s and adults’ information processing for simple symbolic and non-symbolic numeric decisions. Journal of Experimental Child Psychology, 150, 48-71.
2015
McKoon, G. & Ratcliff, R. (2015). Cognitive theories in discourse-processing research. In E.J. O’Brien, A.E. Cook, & R.F. Lorch, Jr., Inferences during reading. Cambridge: Cambridge University Press.
Ratcliff, R. & McKoon, G. (2015). Aging effects in item and associative recognition memory for pictures and words. Psychology and Aging, 30, 669-674.
Ratcliff, R., Smith, P.L., & McKoon, G. (2015). Modeling regularities in response time and accuracy data with the diffusion model. Current Directions in Psychological Science, 24, 458-470.
Ratcliff, R., Thompson, C.A., & McKoon, G. (2015). Modeling individual differences in response time and accuracy in numeracy. Cognition, 137, 115-136.
2014
Smith, P. L., Ratcliff, R., & McKoon, G. (2014). The diffusion model is not a deterministic growth model: Comment on Jones and Dzhafarov (2013). Psychological Review, 121, 679-688.
2013
McKoon, G., & Ratcliff, R. (2013). Aging and predicting inferences: A diffusion model analysis. Journal of Memory and Language, 68, 240-254.
2012
McKoon, G., & Ratcliff, R. (2012). Aging and IQ effects on associative recognition and priming in item recognition. Journal of Memory and Language, 66, 416-437.
Starns, J.J., Ratcliff, R., & McKoon, G. (2012). Evaluating the unequal-variability and dual-process explanations of zROC slopes with response time data and the diffusion model. Cognitive Psychology, 64, 1-34.
Starns, J.J., Ratcliff, R., & McKoon, G. (2012). Modeling single versus multiple systems in implicit and explicit memory. Trends in Cognitive Sciences, 16, 195-196.
2011
McKoon, G., & Love, J. (2011). Verbs in the lexicon: Why is hitting easier than breaking? Language and Cognition, 3, 313-330.
Love, J., & McKoon, G. (2011). Rules of engagement: Incomplete and complete pronoun resolution. Journal of Experimental Psychology: Learning, Memory, and Cognition, 37, 874-887.
Ratcliff, R., Thapar, A., & McKoon, G. (2011). Effects of aging and IQ on item and associative memory. Journal of Experimental Psychology: General, 140, 464-487.
2010
Love, J., McKoon, G., & Gerrig, R.J. (2010). Searching for Judy: How small mysteries affect narrative processes and memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 36, 790-796.
Ratcliff, R., Thapar, A., & McKoon, G. (2010). Individual differences, aging, and IQ in two-choice tasks. Cognitive Psychology, 60, 127-157.
White, C. N., Ratcliff, R., Vasey, M. W., & McKoon, G. (2010). Anxiety enhances threat processing without competition among multiple inputs: A diffusion model analysis. Emotion, 10, 662-677.
White, C. N., Ratcliff, R., Vasey, M. W., & McKoon, G. (2010). Using diffusion models to understand clinical disorders. Journal of Mathematical Psychology, 54, 39-52.
2009
Gerrig, R.J., Love, J., & McKoon, G. (2009). Waiting for Brandon: How readers respond to small mysteries. Journal of Memory and Language, 60, 144-153.
White, C., Ratcliff, R., Vasey, M. & McKoon, G. (2009). Dysphoria and memory for emotional material: A diffusion model analysis. Cognition and Emotion, 23, 181-205.
2008
McKoon, G., & Ratcliff, R. (2008). Meanings, propositions, and verbs. Psychonomic Bulletin and Review, 15, 592-597.
Ratcliff, R., & McKoon, G. (2008). Passive parallel automatic minimalist processing. In, Better than Conscious? Decision Making, the Human Mind, and Implications for Institutions, C. Engel & W. Singer, (Eds.), Cambridge, MA: MIT Press.
Ratcliff, R., & McKoon, G. (2008). The diffusion decision model: Theory and data for two-choice decision tasks. Neural Computation, 20, 873-922.
Ratcliff, R., Schmiedek, F., & McKoon, G. (2008). A diffusion model explanation of the worst performance rule for reaction time and IQ. Intelligence, 36, 10-17.
Wagenmakers, E-J., Ratcliff, R., Gomez, P., & McKoon, G. (2008). A diffusion model account of criterion shifts in the lexical decision task. Journal of Memory and Language, 58, 140-159.
2007
Ratcliff, R., Thapar, A., & McKoon, G. (2007). Application of the diffusion model to two-choice tasks for adults 75-90 years old. Psychology and Aging, 22, 56-66.
McKoon, G. & Ratcliff, R. (2007). Interactions of meaning and syntax: Implications for models of sentence comprehension. Journal of Memory and Language, 56, 270-290.
2006
Ratcliff, R., Thapar, A., & McKoon, G. (2006). Aging and individual differences in rapid two-choice decisions. Psychonomic Bulletin and Review, 13, 626-635.
Ratcliff, R., Thapar, A., & McKoon, G. (2006). Aging, practice, and perceptual tasks: A diffusion model analysis. Psychology and Aging, 21, 353-371.
2005
McKoon, G. & Ratcliff, R. (2005). “Meaning through Syntax” in sentence production and comprehension: Reply to McRae et al. (2005). Psychological Review, 112, 1032-1039.
Ratcliff, R., Thapar, A., Smith, P. L., & McKoon, G. (2005). Aging and response times: A comparison of sequential sampling models. In, Measuring the Mind: Speed, Control, and Age, (pp. 3-32), J. Duncan, P. McLeod, & L. Phillips (Eds.), Oxford University Press: Oxford, England.
2004
Ratcliff, R., Thapar, A., Gomez, P. & McKoon, G. (2004). A diffusion model analysis of the effects of aging in the lexical-decision task. Psychology and Aging, 19, 278-289.
Ratcliff, R., Thapar, A., & McKoon, G. (2004). A diffusion model analysis of the effects of aging on recognition memory. Journal of Memory and Language, 50, 408-424.
Ratcliff, R., Spieler, D. & McKoon, G. (2004). Analysis of group differences in processing speed: Where are the models of processing? Psychonomic Bulletin and Review, 11, 755-769.
Ratcliff, R., Gomez, P., & McKoon, G. (2004). A diffusion model account of the lexical decision task. Psychological Review, 111, 159-182.
2003
Thapar, A., Ratcliff, R., & McKoon, G. (2003). A diffusion model analysis of the effects of aging on letter discrimination. Psychology and Aging, 18, 415-429.
Ratcliff, R., Thapar, A. & McKoon, G. (2003). A diffusion model analysis of the effects of aging on brightness discrimination. Perception and Psychophysics, 65, 523-535.
McKoon, G. & Ratcliff, R. (2003). Meaning through syntax: Language comprehension and the reduced relative clause construction. Psychological Review, 110, 490-525.
2002
McKoon, G. & Macfarland, T. (2002). Event templates in the lexical representations of verbs. Cognitive Psychology, 45, 1-44.
2001
Gerrig, R., & McKoon, G. (2001). Memory processes and experiential continuity. Psychological Science, 12, 82-86.
Ratcliff, R., & McKoon, G. (2001). A multinomial model for short-term priming in word identification. Psychological Review, 108, 835-846.
Ratcliff, R., Thapar, A., & McKoon, G. (2001). The effects of aging on reaction time in a signal detection task. Psychology and Aging, 16, 323-341.
McKoon, G., & Ratcliff, R. (2001). Counter model for word identification: A reply to Bowers (1999). Psychological Review, 108, 674-681.
2000
Rouder, J.N., Ratcliff, R., & McKoon, G. (2000). A neural network model of implicit memory for object recognition. Psychological Science, 11, 13-19.
Ratcliff, R., Spieler, D. & McKoon, G. (2000). Explicitly modeling the effects of aging on response time. Psychonomic Bulletin and Review, 7, 1-25.
Ratcliff, R., & McKoon, G. (2000). Modeling the effects of repetition and word frequency in perceptual identification. Psychonomic Bulletin and Review, 7, 713-717.
Ratcliff, R., & McKoon, G. (2000). Memory models. In E. Tulving and F.I.M. Craik (Eds.), pp. 571-582. Oxford Handbook of Memory, Oxford University Press: New York.
1999
Ratcliff, R., Van Zandt, T., & McKoon, G. (1999). Connectionist and diffusion models of reaction time. Psychological Review, 106, 261-300.
1998
Gerrig, R., & McKoon, G. (1998). The readiness is all: The functionality of memory-based text processing. Invited article, Discourse Processes, 26, 67-86.
McKoon, G., & Ratcliff, R. (1998). Memory based language processing: Psycholinguistic research in the 1990s. Annual Review of Psychology, 49, 25-42.
1997
Ratcliff, R., Allbritton, D.W., & McKoon, G. (1997). Bias in auditory priming. Journal of Experimental Psychology: Learning, Memory, and Cognition, 23, 143-152.
Ratcliff, R., & McKoon, G. (1997). A counter model for implicit priming in perceptual word identification. Psychological Review, 104, 319-343.
1996
Allbritton, D.W., McKoon, G., & Ratcliff, R. (1996). Reliability of prosodic cues for resolving syntactic ambiguity. Journal of Experimental Psychology: Learning, Memory, and Cognition, 22, 714-735.
McKoon, G., Allbritton, D.W., & Ratcliff, R. (1996). Sentential context effects on lexical decisions with a cross-modal instead of an all-visual procedure. Journal of Experimental Psychology: Learning, Memory, and Cognition, 22, 1494-1497.
McKoon, G., Gerrig, R.J. & Greene, S.B. (1996). Pronoun resolution without pronouns: Some consequences of memory based text processing. Journal of Experimental Psychology: Learning, Memory, and Cognition, 22, 919-932.
McKoon, G., & Ratcliff, R. (1996). Separating implicit from explicit retrieval processes in perceptual identification. Consciousness and Cognition, 5, 500-511.
Ratcliff, R., & McKoon, G. (1996). Bias effects in implicit memory tasks. Journal of Experimental Psychology: General, 125, 403-421.
1995
Allbritton, D.W., McKoon, G., & Gerrig, R. (1995). Metaphor-based schemas and text representations: Making connections through conceptual metaphors. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 612-625.
Greene, S.B., & McKoon, G. (1995). Telling something we can’t know: Experimental approaches to verbs exhibiting implicit causality. Psychological Science, 6, 262-270.
McKoon, G., & Ratcliff, R. (1995). The minimalist hypothesis: Directions for research. In Weaver, C.A., Mannes, S., & Fletcher, C.R. (Eds.), Discourse comprehension: Essays in honor of Walter Kintsch. Hillsdale, NJ: Lawrence Erlbaum Associates.
McKoon, G., & Ratcliff, R. (1995). Conceptual combinations and relational contexts in free association and in priming in lexical decision. Psychonomic Bulletin and Review, 2, 527-533.
McKoon, G., & Ratcliff, R. (1995). How should implicit memory phenomena be modeled? Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 777-784.
Ratcliff, R., & McKoon, G. (1995). Sequential effects in lexical decision: Tests of compound cue retrieval theory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 1380-1388.
Ratcliff, R., & McKoon, G. (1995). Bias in the priming of object decisions. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 754-767.
Ratcliff, R., Van Zandt, T., & McKoon, G. (1995). Process dissociation, single process theories, and recognition memory. Journal of Experimental Psychology: General, 124, 352-374.
1994
McKoon, G. & Ratcliff, R. (1994). Sentential context and on-line lexical decision. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20, 1239-1243.
Ratcliff, R., & McKoon, G. (1994). Retrieving information from memory: Spreading activation theories versus compound cue theories. Psychological Review, 101, 177-184.
Ratcliff, R., McKoon, G. & Tindall, M.H. (1994). Empirical generality of data from recognition memory receiver-operating characteristic functions and implications for the global memory models. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20, 763-785.
McKoon, G., Ratcliff, R., & Ward, G. (1994). Testing theories of language processing: An empirical investigation of the on-line lexical decision task. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20, 1219-1228.
Greene, S.B., Gerrig, R.J., McKoon, G., & Ratcliff, R. (1994). Unheralded pronouns and the management of common ground. Journal of Memory and Language, 33, 511-526.
1993
McKoon, G., Ward, G., Ratcliff, R., & Sproat, R. (1993). Morphosyntactic and pragmatic factors affecting the accessibility of discourse entities. Journal of Memory and Language, 32, 56-75.
McKoon, G., Ratcliff, R., Ward, G, & Sproat, R. (1993). Syntactic prominence effects on discourse processing. Journal of Memory and Language, 32, 593-607.
McKoon, G., Greene, S., & Ratcliff, R. (1993). Discourse models, pronoun resolution, and the implicit causality of verbs. Journal of Experimental Psychology: Learning, Memory, and Cognition, 19, 1-13.
1992
McKoon, G. & Ratcliff, R. (1992). Inference during reading. Psychological Review, 99, 440-466.
McKoon, G. & Ratcliff, R. (1992). Spreading activation versus compound cue accounts of priming: Mediated priming revisited. Journal of Experimental Psychology: Learning Memory and Cognition, 18, 1155-1172.
Greene, S.B., McKoon, G. & Ratcliff, R. (1992). Pronoun resolution and discourse models. Journal of Experimental Psychology: Learning, Memory, and Cognition, 18, 266-283.
1991
Ratcliff, R. & McKoon, G. (1991). Using ROC data and priming results to test global memory models. In S. Lewandowsky and W.E. Hockley (Eds.), Relating Theory and Data: Essays on Human Memory in Honor of Bennet B. Murdock, Jr. (pp.279-296). Hillsdale, NJ: Erlbaum.
Ward, G., Sproat, R., & McKoon, G. (1991). A pragmatic analysis of so-called anaphoric islands. Language, 67, 439-474.
1990
McKoon, G. & Ratcliff, R. (1990). Dimensions of inference. In A. Graesser and G. Bower (Eds.), The Psychology of Learning and Motivation: Vol. 25. Inferences and text comprehension (pp 313-328). New York: Academic Press.
McKoon, G. & Ratcliff, R. (1990). Textual inferences: Models and measures. In D.A. Balota, G.B. Flores d’Arcais, & K. Rayner (Eds.), Comprehension Processes in Reading (pp. 403-421). Hillsdale, N.J.: Erlbaum.
1989
Ratcliff, R. & McKoon, G. (1989). Similarity information versus relational information: Differences in the time course of retrieval. Cognitive Psychology, 21, 139-155.
Ratcliff, R., McKoon, G. & Verwoerd, M. (1989). A bias interpretation of facilitation in perceptual identification. Journal of Experimental Psychology: Learning, Memory, and Cognition, 15, 378-387.
Ratcliff, R. & McKoon, G. (1989). Memory models, text processing, and cue-dependent retrieval. In F.I.M. Craik & H.L. Roediger (Eds.), pp 73-92. Varieties of memory and consciousness: Essays in honour of Endel Tulving. Hillsdale, NJ: Erlbaum.
McKoon, G., & Ratcliff, R. (1989). Semantic associations and elaborative inference. Journal of Experimental Psychology: Learning, Memory, and Cognition, 15, 326-338.
McKoon, G. & Ratcliff, R. (1989). Assessing the occurrence of elaborative inference with recognition: Compatibility checking vs compound cue theory. Journal of Memory and Language, 28, 547-563.
McKoon, G. & Ratcliff, R. (1989). Inferences about Contextually-Defined Categories. Journal of Experimental Psychology: Learning, Memory, and Cognition, 15, 1134-1146.
McKoon, G., Ratcliff, R., & Seifert, C. (1989). Making the connection: Generalized knowledge structures in story understanding. Journal of Memory and Language, 28, 711-734.
1988
Greene, S., Ratcliff, R, & McKoon, G. (1988). A flexible programming language for cognitive psychology experiments. Behavior Research Methods, Instruments, & Computers, 20, 119-128.
Steve Greene won the Student Award from the Society for Computers in Psychology for this article.
McKoon, G. & Ratcliff, R. (1988). Contextually relevant aspects of meaning. Journal of Experimental Psychology: Learning, Memory, and Cognition, 14, 331-343.
Ratcliff, R. & McKoon, G. (1988). A retrieval theory of priming in memory. Psychological Review, 95, 385-408.
1986
McKoon, G. & Ratcliff, R. (1986). Inferences about predictable events. Journal of Experimental Psychology: Learning, Memory and Cognition, 12, 82-91.
McKoon, G. & Ratcliff, R. (1986). The automatic activation of episodic information in a semantic memory task. Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 108-115.
McKoon, G., Ratcliff, R., & Dell, G. (1986). A critical evaluation of the semantic/episodic distinction. Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 295-306.
Ratcliff, R. & McKoon, G. (1986). More on the distinction between episodic and semantic memories. Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 312-313.
Seifert, C.M., Abelson, R.P., & McKoon, G. (1986). The role of thematic knowledge structures in reminding. In J.A. Galambos & R.P. Abelson (Eds.), Knowledge Structures. Hillsdale, NJ: Erlbaum.
Seifert, C., McKoon, G., Abelson, R.P., & Ratcliff, R. (1986). Memory connections between thematically similar episodes. Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 220-231.
1985
McKoon, G., Ratcliff, R., & Dell, G. (1985). The role of semantic facilitation in episodic retrieval. Journal of Experimental Psychology: Learning, Memory, and Cognition, 11, 742-751.
Ratcliff, R., Hockley, W., & McKoon, G. (1985). Components of activation: Repetition and priming effects in lexical decision and recognition. Journal of Experimental Psychology: General, 114, 435-450.
1984
McKoon, G. & Ratcliff, R. (1984). Priming and on-line text comprehension. In: Kieras, D.E., & M.A. Just (Eds.), New Methods in Reading Comprehension Research (pp. 119-128). Hillsdale, N.J.: Erlbaum.
McNamara, T., Ratcliff, R., & McKoon, G. (1984). The mental representation of knowledge acquired from maps. Journal of Experimental Psychology: Learning, Memory & Cognition, 10, 723-732.
1983
Dell, G., McKoon, G., & Ratcliff, R. (1983). The activation of antecedent information during the processing of anaphoric reference in reading. Journal of Verbal Learning and Verbal Behavior, 22, 121-132.
1982
Ratcliff, R. & McKoon, G. (1982). Speed and accuracy in the processing of false statements about semantic information. Journal of Experimental Psychology: Learning, Memory and Cognition, 8, 16-36.
1981
Dell, G., Ratcliff, R. & McKoon, G. (1981). Study and test repetition effects in item recognition priming. American Journal of Psychology, 94, 497-511.
McKoon, G. (1981). The representation of pictures in memory. Journal of Experimental Psychology: Human Learning and Memory, 7, 216-221.
McKoon, G. & Ratcliff, R. (1981). The comprehension processes and memory structures involved in instrumental inference. Journal of Verbal Learning and Verbal Behavior, 20, 671-682.
Ratcliff, R. & McKoon, G. (1981). Does activation really spread? Psychological Review, 88, 454-462.
Ratcliff, R. & McKoon, G. (1981). Automatic and strategic priming in recognition. Journal of Verbal Learning and Verbal Behavior, 20, 204-215.
1980
McKoon, G., & Ratcliff, R. (1980). Priming in item recognition: The organization of propositions in memory for text. Journal of Verbal Learning and Verbal Behavior. 19, 369-386.
McKoon, G. & Ratcliff, R. (1980). The comprehension processes and memory structures involved in anaphoric reference. Journal of Verbal Learning and Verbal Behavior, 19, 668-682.
1979
McKoon, G. & Ratcliff, R. (1979). Priming in episodic and semantic memory. Journal of Verbal Learning and Verbal Behavior, 18, 463-480.
Ratcliff, R., & McKoon, G. (1979). Roots of modern cognitive psychology. (Review of Cognitive Psychology and Information Processing by Lachman, Lachman, & Butterfield). Contemporary Psychology, 24, 917-918.
1978
Ratcliff, R. & McKoon, G. (1978). Priming in item recognition: Evidence for the propositional structure of sentences. Journal of Verbal Learning and Verbal Behavior, 17, 403-417.
1974
Kintsch, Crothers, Glass, Keenan, McKoon, & Monk. (1974). The representation of meaning in memory. Hillsdale, NJ: Erlbaum.
McKoon, G., & Keenan, J.M. (1974). Response latencies to explicit and implicit statements as a function of the delay between reading and test. In W. Kintsch (Ed.), The representation of meaning in memory. Hillsdale, NJ: Erlbaum.
1977
McKoon, G. (1977). Organization of information in text memory. Journal of Verbal Learning and Verbal Behavior, 16, 247-260.
1975
Kintsch, W., Kozminsky, E., Streby, W.J., McKoon, G., & Keenan, J.M. (1975). Comprehension and recall of text as a function of content variables. Journal of Verbal Learning and Verbal Behavior, 14, 196-214.
1973
Hinrichs, J.V., & McKoon, G. (1973). Set size and order requirements in immediate memory. Memory and Cognition, 1, 73-77.
1971
Hinrichs, J.V., & McKoon, G. (1971). Order and number requirements in immediate serial recall. Journal of Experimental Psychology, 87, 215-219.